Hydrology Bowla Nand Prayag

Uttaranchal Jal Vidyut Nigam Ltd

300MW Bowala Nand Prayag Hydro-Electric Project

Detailed Project Report

April 2007

Volume I – Section 4

Hydrology

Halcrow Consulting India Limited

Halcrow Consulting India Limited 153 Okhla Industrial Estate Phase 3, New Delhi 110020

Tel +91 (11)4650 1500 Fax +91 (11)4650 1599

www.halcrow.com

Halcrow Consulting India Limited has prepared this report in

accordance with the instructions of their client, Uttaranchal Jal

Vidyut Nigam, for their sole and specific use. Any other persons

who use any information contained herein do so at their own risk.

© Halcrow Consulting India Limited 2015




April 2007


Hydrology

Halcrow Consulting India Limited

Halcrow Consulting India Limited 153 Okhla Industrial Estate Phase 3, New Delhi 110020

Tel +91 (11) 4650 1500 Fax +91 (11) 4650 1599

www.halcrow.com





Hydrology

Contents Amendment Record

This report has been issued and amended as follows:

Issue Revision Description Date Signed

1 0 Preliminary Draft Feb 06

1 1 First Draft Dec 06

1 2 Revised Jan 07

2 0 Final Apr 07 IWB

2 1 Revised using data up to 2007 Aug 07 IWB

Contents

4 Hydrology 4-1

4.1 General Context 4-1

4.2 Basin Characteristics 4-1

4.3 Climate 4-2

4.4 Availability of Water and Dependable Flows 4-4

4.5 Data analyses 4-5

4.6 Flood Risk Analysis 4-17

4.7 Design Discharge 4-26

TABLES

Table 4-1: Available Gauge & Discharge Data

Table 4-2 Summary of Flood Analysis

FIGURES

Figure 4-1: Mean Monthly Maximum & Minimum Temperatures at Joshimath

Figure 4-2: Annual Rainfall Distribution at Joshimath

Figure 4-3: Matching of Flow-Duration Curves

Figure 4-4: Long-Term Flow-Duration Curves at Chamoli by FDC Method

Figure 4-5: Comparison of FDC Method with Non-Linear Regression Analysis

Figure 4-6: 50% and 90% Dependable Years

Figure 4-7: Comparison of Long-Term Flow-Duration Curves - Present Study v 1992 DPR

Figure 4-8: Catchment Area Characteristics

ANNEXES

Annex 4.1: Observations at Chamoli

Annex 4-2: Observations at Rudraprayag

Annex 4-3: Observations at Joshimath

Annex 4-4: Data Consistency Checks

Annex 4-5: Regression Analysis: Joshimath v Chamoli

Annex 4-6: Estimated Discharge Data for Intake Site

Annex 4-7: Determination of 50% and 90% Dependable Years

Annex 4-8: Regional Flood Data

Annex 4-9: Flood Frequency Analysis

Annex 4-10: Flood Estimate by Unit Hydrograph

300MW Bowala Nand Prayag Hydro Electric Project Detailed Project Report

4-1

4 Hydrology

4.1 General Context

The River Alaknanda, which along with Bhagirathi and other tributaries constitutes river

Ganga, originates in glacial regions of the Himalayas in the extreme northern parts of the

district of Chamoli in Uttaranchal.

The proposed barrage site is situated on the River Alaknanda at Bowala, which is

approximately 208 km from Rishikesh. At this site the catchment area is 5,590 km2, of which

2,740 km2 is snow bound.

This chapter describes the study of the hydrology of the catchment area and the

methodology adopted for establishing various parameters, which are basic inputs for the

project planning and design. The hydrological analysis has been carried out to assess the

availability of water for power generation by establishing long term discharge data and to

establish design floods for various components of the project.

All hydrological studies have been based primarily on records, data and criteria presented in

the Detailed Project Report-1992 (DPR-1992) and on additional up-to-date available records.

The studies consist principally of:

• A review of previous hydrological studies.

• Updating the hydrology with recently available data.

• Verification of the quality and completeness of meteorological and

hydrometric data.

• Generation of a long-term flow series for the Alaknanda River at the intake

site.

• Comparison with the results of previous studies

• Analysis of design floods by various methods.

4.2 Basin Characteristics

Bowala Nand Prayag Barrage and Intake are located at the River Alaknanda, which is one of

the main tributaries of the River Ganges in the state of Uttaranchal. It originates from the twin

glaciers of Bhagirath Kharak and Satopanth near the holy shrine of Badrinah at an elevation

of about 3750 m a.s.l. Initially it flows in an easterly direction until it is joined by the Saraswati

River at Mana. From Mana the general direction of flow is South South-East to Joshimath

where it is joined by the major tributary of Dhauliganga. From Joshimath the river flows

South West, and then West until it joins the Bhagirathi River at Devprayag to form the

Ganga.

The catchment of River Alaknanda up to the intake site for Bowala Nand Prayag extends

from latitude 30° 24’N to 31° 02’N and longitude 79° 12’E to 80° 15’E. It is generally

mountainous, and about 50% is snow covered. The highest altitude in the catchment is over

7800 m a.s.l. (the peak of Nanda Devi) and the lowest point near the intake site is at 1025 m.


4-2

The catchment area has been remeasured from the Survey of India 1:250,000 topo sheet

with the following results.

Previous Studies Present Study

Total Catchment Area 5,590 km2 5,590 km

2

Snowbound Catchment 2,890 km2 2,740 km

2

Rainfed Catchment 2,700 km2 2,850 km

2

The area of snow fed catchment has been measured as the area enclosed by the 4,500m

contour. The difference between the previous and present studies is thought to be due to the

more accurate measurement for the present study, which was measured using AutoCAD.

Drawing no WH/BNPP/007 in Volume III of this report shows the catchment area of the

Project.

4.3 Climate

4.3.1 Temperature

The climate of the area is generally temperate and varies with elevation. It is warm in

summer, humid in monsoon and cool in winter months. The winter months are from

December to March. The summer or pre monsoon months are from April to May. The

monsoon months are from June to September. The post monsoon months are from October

to November. The nearest Indian Meteorological Department (IMD) observatory is at

Joshimath which is approximately 30 km from the Intake Site at an elevation of 1875m. The

lowest temperature at Joshimath of -15° C was recorded in the month of January 1974 and

the highest temperature of 34° C was recorded in the month of June 1978. The mean

monthly maximum and minimum temperatures at Joshimath are shown in Figure 4.1.

Temperatures at the intake site, which is about 850m lower than Joshimath, will be about

5.5° C higher than the temperatures at Joshimath on average.

Figure 4-1: Mean Monthly Maximum & Minimum Temperatures at Joshimath

10.912.0

17.5

21.3

23.725.0

23.5 23.122.4

20.3

16.9

13.5

4.0

6.6

10.7

14.6

16.716.516.2

2.03.0

6.3

10.9

13.6

0

5

10

15

20

25

30

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Tem

pera

ture

(0C

)

Maximum Mean Monthly Temperature

Minimum Mean Monthly Temperature


4-3

4.3.2 Precipitation

There are several rain gauge stations established in the upper part of the catchment area,

however, due to the difficulty of access the records from these stations are generally

incomplete, particularly during the winter months. The rain guage at Joshimath provides a

rainfall record from 1958 to 2003 which is more or less complete, and which, due to its

central location in the catchment, gives an indication of the annual rainfall distribution.

The mean annual rainfall in the catchment estimated from isohyetal map of IMD is 1050 mm.

The maximum rainfall is observed in monsoon months. In monsoon months rainfall is due to

south west monsoons which normally strike the Garhwal Himalayas towards the end of June

and withdraws from the region towards the end of September. The precipitation is due to the

passage of depressions and or cyclonic storms from the Bay of Bengal over the region.

These disturbances after originating from the Bay of Bengal move in north west direction,

after reaching west Madhya Pradesh, south Rajasthan move in a north to northeast direction

and strike the Garhwal Himalayas. The winter precipitation in the basin is due to western

disturbances advancing from Afghanistan and West Pakistan.

Figure 4-2: Annual Rainfall Distribution at Joshimath

103.4115.1

77.5

60.5

98.1

245.9

214.0

112.9

43.5

15.5

33.7

0

50

100

150

200

250

300

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov

Me

an

Mo

nth

ly R

ain

fall

(m

m)

4.3.3 Source of Runoff

The catchment is fed by both snow and rain. A significant percentage of the runoff is from

snow- and glacier-melt which constitute a potential reservoir. Winter precipitation which

occurs in the form of snow accumulates until early summer. As summer advances, the

accumulation melts to release water in to the stream. Glaciers and permanent snowfields are

located at altitudes above about 4800 m. During winter season the seasonal snowline drops

to a height of about 2000 m.


4-4

4.3.4 Evaporation

No records of lake evaporation or pan evaporation are available for the project area.

However, since the project is planned as a run of river scheme, with provision only for daily

storage for peaking, the evaporation losses can be safely neglected.

4.4 Availability of Water and Dependable Flows

4.4.1 Available Data

Though no gauge discharge data is available for the barrage site, data from 1971 to 1982 is

available at Chamoli, which is located 5 km downstream of the barrage site. Discharge data

of River Ganga at Raiwala is also available from 1945-46 to 1978-79. At Raiwala the

catchment of River Ganga is 22,936 km2 (out of this 5,988 km

2 is snow bound).

Data is also available for the gauging stations at Rudraprayag, downstream of the project

site and at Joshimath, upstream of the project site. The locations of stations and the period

of availability of discharge data for the Alaknanda and the Ganga Rivers is given below.

Table 4-1: Available Gauge & Discharge Data

River Location of

Station

Catchment

Area

From To

km2

Alaknanda Joshimath 4,508 1971-72 2006-07

Alaknanda Chamoli 5,590

(at Bowala)

1970-71 1981-82

Alaknanda Rudraprayag 9,042 1977-78 2006-07

Ganga Raiwala 22,936 1945-46 1978-79

The DPR of 1992 has used the discharges from 1970-71 to 1981-82 at Chamoli, for

computing the annual run off for the Project. But since the data is for a short period the

record has been extended by transferring discharges from Raiwala.

For this the runoff of ten day period at Chamoli has been compared with the corresponding

runoff at Raiwala, taking into account the time lag.

The stations at Joshimath and Rudraprayag are much closer to Bowala than Raiwala and

are of sufficient duration (36 years and 30 years respectively) to provide a reliable record, so

it is proposed to use the data from these stations to augment the time series at Chamoli.

Discharge data for Joshimath, Chamoli and Rudraprayag is presented in Annexes 4-1, 4-2

and 4-3.

The hydrological parameters for the scheme in the present study are thus estimated directly

from the discharges observed on the Alaknanda River and there is no need to subvent this

material with rainfall or snowmelt observations. These data have been used only to indicate

the wider climatological context of the Project, as reported above, and for checking the

consistency of the discharge data by rainfall-runoff relationship.


4-5

4.5 Data analyses

Hydrological time series may exhibit trends referred to as inconsistencies or non-

homogeneities. Inconsistencies result from changes in the amount of systematic errors

married with recording of data, such as those arising from changes in instrumentation or

observational practices. Non-homogeneity of the data is defined as the change in statistics of

the data set which are caused by natural or man-made changes like change in landuse,

water use and climatic change.

The quality and quantity of the data for the station Joshimath are controlled and assured in

data analysis. It refers to the internal and external pre-processing of data. The external is

checked and verified from the double mass curve analysis where as, internally the data itself

is analysed by conducting the tests as described in the following sub-sections. In toto, 33

years of annual flood data are available for analysis.

4.5.1 Test for randomness

A random series is the one in which the value of the next discrete value is unknown. There

are number of statistical tests to check the randomness of the data series i.e. turning point

test, difference sign test, Run test, Serial rank Correlation test .etc. The Turning Point Test is

applied to check the randomness of the series at 5% significance level. The number of

turning points is the total number of crest or trough in the sample of peak annual flood

values.

Qt is the turning point and is defined in the form,

Qt is crest when Qt-1 < Qt > Qt +1

Qt is trough when Qt -1 > Qt < Qt +1

The randomness of data is determined by the normal variate of the data and is given by,

−

=σ

µαυ

where, α

is the total number of crests and troughs.

µ

is the mean such that

( )23

2−= Nµ

and N is the sample size

σ

is the standard deviation of the sample.

If υ < 1.9, the series is random at 5% significant level. The computations for the same have

been tabulated and results are depicted in Annex - 4-4

4.5.2 Test for trend: Spearman’s rank correlation method

The presence or absence of trend is determined by using Spearman’s rank correlation

method. The co-efficient is denoted by ρ .The 33 years of peak annual flood data are

converted to ranks before computing the coefficient and then, the data is sorted in

descending order ranking the highest value as one. The differeneces Di between the ranks

of each observation on the two variables are calculated and. The Spearman’s rank

correlation coefficient , ρ is expressed as,


4-6

( )1

61

2

2

−−= ∑

nn

Diρ

The test statistics t is given by,

−−

=21

2

ρρ n

t

Where n represents the number of observations in both the equation. The test variable t has

a Student’s t-distribution with degree of freedom, 2−= nν .

The critical region with a 5% signifacnce level in the Student’s t- distribution is expressed as,

{ } { }∞+∞− %),5.97,(%)5.2,(, νν tUt

Therefore, the data has no trend if

%)5.97,(%)5.2,( νν ttt <<

In the current study, the method is applied for the data of Joshimath duly transposed to BNP

site and no trend is found in the peak annual flood data. The results of the same have been

tabulated in Annex-4-5

4.5.3 Test for outliers

Outliers are the observations that deviate significantly from the remaining data points of the

sample set. The test for ouliers holds a stand while assessing the retention, modification and

deletion of these outliers because any such treatment would affect the statistical parameters

of the data.

The skewness, Sk of the annual peak flood of BNP set rules to check the outliers

categorizing them into high outliers and low outliers and the following expressions define the

limits of skewness that is applicable for the data set.

If Sk < -0.4 then, check for Low outliers first

If Sk > +0.4 then, check for High outliers first

If -0.4< Sk <+0.4 then, check for High outliers first

The threshold values of the outliers are governed by the following equations:

Low outlier threshold = exp[ Rp(log)Avg - Kn * σRp(log) ]

High outlier threshold = exp[ Rp(log)Avg +Kn * σRp(log) ]

where, Rp(log)Avg is the mean of log transformed annual peak flood.

σRp(log) is standard deviation of Rp(log) series

n is the number of years

Kn is the outlier test values for 10% significance level for a Normal distribution


4-7

4.5.4 Test for stability of variance: F-test

F-test is taken to assess the stability of variance in which the same sample of data is split up

into two different series randomly chosen without affecting the order of the data set.

However, in the current study the bar chart showing the peak annual rainfall series is

indicative of peaks to be considered in the first series or the second one. The first and

second subsets are termed as X1 and X2.

The variances of each of the two series are represented as 2

1sand

2

2s.

The test statistics is given by,

2

2

2

1

s

sFt =

The investigation of the data series of BNP results in differences in the variance and

therefore, a confidence limit for stability of the variance using Fisher –F distribution is also

observed and found that the test statistics are confined to the domain which is essentially

based on the degree of freedom of each data series.

From the Fisher-F distribution, the critical region with 5% significance level is set as,

{ } { }∞%),5.97,,(%)5.2,,(,0 2121 νννν FUF

where, 1ν and 2ν

are the respective numbers of degrees of freedom of the numerator and

the denominator.

11 2211 −=−= nandn νν

where, 21 nandn are the numbers of observation in each sub-set.

The results of the F-test for all the abovementioned three stations have been computed and

are shown in Annex-4-6 which also includes the result of t-test described below.

4.5.5 Test for stability of mean: t-test

The same parted series investigated on F-test is subjected to the test for stability of the

mean and is widely known as t-Test. This test is based on null hypothesis that when the two

data series aforesaid are normally distributed then, the difference between the mean values

of the two series is equal to zero. Assuming this to be true the test statistic has a Student’s t

distribution.

The subsets X1 and X2 used in the F-test are tested for stability of mean.

Taking 21 XandX as the averages , the test statistic is given by,

( ) ( ) 5.0

2121

2

22

2

1

21

11

2

111

+

−+

−+−

−=

nnnn

snsn

XXt

where , in is the number of data in the subset


4-8

iX is the mean of the subset i

2

is is the variance of the subset i

From the Student’s- t distribution, the critical region with 5% significance level is set as,

{ } { }∞+∞− %),5.97,(%)5.2,(, νν tUt

where, ν is the number of degrees of freedom, 221 −+= nnν

From the above statistics, the stability is inferred and the results of test for all the three

stations are included in Annex- 4-7

4.5.6 Consistency Check.

This examines the mean 10-daily discharge time series at Joshimath, Chamoli and

Rudraprag and has the objective of assessing data quality and therefore the confidence that

can be attached to the results, particularly with respect to the assurance of the flows

available for diversion. These time-series are initially examined to ensure that they are

statistically “stationary”, that is that they contain no systematic trends or inconsistencies over

the period of record, which would otherwise lead to bias and potential inaccuracies in the

results of interest. The consistency check has been carried out using both internal checks

(runoff-runoff relationships by regression analysis and double mass curve methods) and

external checks (rainfall-runoff relationship).

a) Regression Analysis

This test has been performed by simple regression analysis of the data from different

stations over the common period of record. Both linear and non-linear regression methods

were explored and the best-fit curves gave the following result:

Stations Best – fit equation

R2

Coefficient of

Correlation

R

Joshimath v Rudraprayag y = 0.2453x1.1139

0.84 0.92

Joshimath v Chamoli y = 1.3382x0.9039

0.91 0.95

Chamoli v Rudraprayag y = 0.5996x - 6.6157 0.90 0.95

Details of this analysis are given in Annex 4-8. These coefficients of correlation show that the

data from the three stations have a satisfactory degree of consistency.

b) Double Mass Curve

The double mass curves for Joshimath v Chamoli v Joshimath and Joshimath v Rudraprayag

have been prepared. The calculations are appended in Annex 4- 4 of this report. From the

trend of the double mass curves it can be concluded that the data from the three stations is

generally consistent, although the year 1998-99 shows an anomaly between the stations at

Joshimath and Rudraprayag.

c) Rainfall-Runoff


4-9

The calculations are appended in Annex 4-4 of this report. The runoff from the snow fed

catchment has been calculated using the method described in Ref [1]. This figure is

deducted from the total runoff calculated from the gauge & discharge data to give the runoff

from the rainfed area, which is then compared with the mean annual rainfall at Joshimath

with the following result:

Mean Annual Runoff at Joshimath (rain fed catchment) = 1120mm

Mean Annual Rainfall at Joshimath = 1160mm

This shows that the discharges measured at Joshimath are consistent with the rainfall and

may be used for further analysis

With the consistency of the gauge and discharge data established, the next step is to

augment the discharge data for Chamoli by estimating the flows from 1982 to 2002 using the

data at the Rudraprag and Joshimath stations.

4.5.7 Procedures used to extend the daily flows observed at Chamoli using data at the Joshimath

gauge upstream.

Three methods of extending the discharge series at Chamoli have been considered:

a) Catchment Area Ratio

The discharges at Bowala intake site were calculated by factoring the discharges at

Joshimath by the Catchment Area Ratio (5590/4672 = 1.196). The results are presented in

Annex 4-6 of this report.

b) Seasonal Non-Linear Regression Analysis

The discharge series at Chamoli was extended using data from Joshimath by means of a

non-linear regression analysis on a seasonal basis. The calculations are presented in Annex

4-5 of this report.

c) Method of Matching Flow-Duration Curves (FDC Method)

Hughes and Smatkhin. (1996) (see Reference [2]) have shown that rather than use

regression analysis directly to estimate the target flows, there are very significant statistical

advantages to “matching” the flow duration curves. The reasons for this are:

• the regression model smoothes the distribution of the estimated flows

(unless the error term is included);

• the relationship between flows at 2 sites is rarely linear, as is assumed

in simple regression;

• the use of the flow duration curves overcomes the non-linear issue and

exploits a knowledge of the probability distribution of the flows at the 2

sites (which is what the FDC’s are).

The flow records available at the two sites are as below, the “target” being the data to be

treated and the “control” the data means for doing so. In this case the objective is to extend

the target time series at Chamoli for the period after September 1982 (when observations at

Chamoli stopped) using the data from Joshimath.

Control Site: Joshimath 1971 – 2002


4-10

Target Site: Chamoli. 1971 – 1982

Between 1971 and 1982 (the common observation period) 408 paired 10-daily observations

at the two sites are available. For the present application and given the available common

sample size at the two sites (408), the FDC’s were computed using every set of paired data

(i.e. giving 408 ordinates at intervals of 0. 25%)

The procedure is illustrated below in Figure 4-3. Given (for example) a mean 10-daily flow of

600 m3/s at the control station, this has an exceedance probability of 21%. The flow with the

same exceedance probability at the target station is 369 m3/s. Where discharge values in the

extended time series at the control site lie between points on the FDC for the common period

the values at the target site are obtained by linear interpolation between the adjacent points.

Where discharge values are greater than the maximum value of the FDC for the common

period values at the target site are obtained by extrapolation using the average ratio between

the two staions.

Figure 4-3: Matching of Flow-Duration Curves

0

200

400

600

800

1000

1200

1400

1600

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

% Exceedence

Dis

ch

arg

e (

cu

me

cs

)

Control Station

Target Station

600

369

21%

Proceeding in this way the missing period of data at the target site (in this case post-1982)

can be estimated.

This method overcomes the non-linear aspects and data smoothing that are usually the

inevitable consequences of simple regression analysis.

Thus there is no “fixed” ratio between flows at the 2 locations across the whole flow range –

thus reflecting reality. Instead the ratio varies as a function of the mutual distribution of flows

in terms of the FDC’s. This approach is simple and statistically efficient and accurate.


4-11

As a diagnostic check, however, the mean ratio of the flows between the 2 sites should

remain the same over the common and treatment periods, unless one was wetter (drier) than

the other. Here:

1978-1982 (common observations = 408): ratio target / control = 1.19

1982-2002 (estimated observations = 708): ratio target / control = 1.20

The long term flow duration curve at Chamoli (from 1971 to 2002) generated in this way,

using data from Joshimath, is compared with the corresponding data derived using data from

Rudraprayag (from 1978 to 2002) in Figure 4-4, below:


4-12

Figure 4-4: Long-Term Flow-Duration Curves at Chamoli by FDC Method

0

200

400

600

800

1000

1200

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Exceedance Probability

Dis

ch

arg

e (

m3/s

)

Data transferred from Rudraprayag

Data transferred from Joshimath

It can be seen that the differences between two Flow-Duration Curves are small. In view of

the relatively short period of common record between Rudraprayag and Chamoli the values

derived from Joshimath are considered to be more reliable.

4.5.8 Comparison of Different Methods for Estimating Discharges at the Intake Site

The discharges at the intake calculated by the above methods are compared in Figure 4.5

below. The coefficient of correlation for the regression analysis was found to be lower than

for the other methods so the results from the regression analysis were discarded. The results

from FDC method compared well with those based on catchment area ratio, however when

the results are compared in chronological order the values for the same period were found to

vary considerably.

In view of this, and because the catchment at Joshimath is 84% of the catchment at Bowala

intake, it is proposed to adopt the discharges determined by catchment area ratio for the

discharge series at the intake site. The estimated 10-daily timeseries at the Intake Site are

presented in Annex 4-6.

.


4-13

Figure 4-5 a): Comparison of FDC Method with Non-Linear Regression Analysis

y = 1.0294x

R2 = 0.9656

0

200

400

600

800

1000

1200

1400

0 100 200 300 400 500 600 700 800 900 1000

Discharge Estimated by Regression Analysis

Dis

ch

arg

e E

sti

mate

d b

y F

DC

Me

tho

d

Figure 4-5 b): Comparison of FDC Method with Catchment Area Ratio Method

y = 1.01x

R2 = 0.99

0

200

400

600

800

1000

1200

1400

1600

0 200 400 600 800 1000 1200 1400 1600

Transferred by Catchment Area Ratio

Tra

ns

ferr

ed

by

FD

C M

eth

od


4-14

Figure 4-5 c): Comparison of FDC Method with Catchment Area Ratio Method

0

200

400

600

800

1000

1200

1400

1600

1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Dis

ch

arg

e (

m3/s

)

Transferred by Cathment Area Ratio

Transferred by FDC Method


4-15

4.5.9 Determination of 50% and 90% Dependable Years

The estimated discharges at the Barrage Site are ranked in descending order according to

the total annual discharge and the exceedance probability for each year is calculated using

Weibull’s formula.

The 50% and 90% dependable years are found to be 1983-84 and 1971-72.

The resulting values are presented in Annex 4-7 and Figure 4-6.

Figure 4-6: 50% and 90% Dependable Years

0

100

200

300

400

500

600

700

800

900

Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May

Dis

ch

arg

e (

m3/s

)

50% year (1983-84)

90% year (1971-72)


4-16

4.5.10 Comparison with Previous Studies

The discharges at the barrage site estimated by the above procedure are expressed as a

long-term flow-duration curve for comparison with the corresponding data that was presented

in the 1992 DPR in Figure 4-7, below.

It can be seen that, although the two curves generally lie close together the discharges

estimated using the latest data from Joshimath are lower than those from the 1992 DPR

during the lean season, but higher during the monsoon season. The most significant

difference is in the values for 90% dependable discharge, which is 35m3/s in the present

analysis, compared with 41m3/s in the 1992 DPR.

Figure 4-7: Comparison of Long-Term Flow-Duration Curves

Present Study v 1992 DPR

0

200

400

600

800

1000

1200

1400

1600

1800

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Exceedance Probability

Dis

ch

arg

e (

m3/s

)

1992 DPR (Data Transferred from Raiwala)

Proposed Discharge Series at Intake (Data Transferred from Joshimath)


4-17

4.6 Flood Risk Analysis

4.6.1 General Issues

It is inevitably difficult to compute floods of such magnitude as those of the Ganga tributaries

with accuracy, and uncertainties over historic flood peaks cannot be avoided. Factors that

complicate a full understanding of the flood characteristics of the basin include the fact that

large areas of the upper basin are snow-bound, at high elevations the terrain is excluded

from normal cloud ranges, and there are many man-made influences on floods, such as

major dams or diversions. Each catchment tends to be individual and not closely similar to

another.

Several approaches can be used to estimate floods of different return periods. These

include:

• Flood Frequency Analysis

• Unit Hydrograph Method

• Empirical Formula

4.6.2 Hydrological Data

The observed peak annual discharges for a number of sites in the region have been made

available and these are given Annex 4-8. The sites for which data is available include

Joshimath, Rudraprayag and Raiwala on the Alaknanda and Ganga rivers.

Daily rainfall records are available for Joshimath and Badrinath stations both of which lie

within the catchment area.

4.6.3 Flood Frequency Analysis

The peak annual flood data for a record of 33 years are transposed to BNP on the basis of

catchment area ratio raising it to a power of 0.75. In order to obtain the instantaneous flood

peaks, the observed flood peaks are increased by 30%. The flood frequency analysis is

conducted by applying, analysis of extremes for annual series (Gumbel type-I and Log

Pearson type –III) and analysis of exceedances for partial duration series)

1) Analysis of extremes

a) Gumbel type-I

The peak annual discharge values are sorted and fitted in extreme value distribution i.e.,

Gumbel type-I and Log Pearson Type-III.

The simplified relation of Gumbel’s distribution is given by,

XT = Xext(avg) + KT * Sext

where, XT estimated flood for a period T

Xext(avg) mean of observed extreme floods

KT Gumbel's factor for varying T


4-18

Sext standard deviation of extreme flood records

The probability of exceedance is given by Gringerton’s formula,

αα

21−+−

=N

mp

where, m rank

α = 0.44 plotting position number by Gringerton

N number of years

The return period, T is the reciprocal of probability of exceedance. The reduced variate y is

calculated as,

[ ])1ln((ln py −−−=

From the mean yN, standard deviation σN of Gumbel variate y and recorded length N, the

factor KT is expressed as,

ext

N

N

T Syy

K *

−=

σ

The computations for XT have been shown for each station in Annexure 4-9 which also

includes results of analysis of exceedance.

b) Log-Pearson type-III

This method is defined by three standard statistical parameters: the mean, standard

deviation and coefficient of skew. These parameters are determined from the logs of 33

years annual peak flood of BNP.

The aforesaid parameters are derived as,

N

yym

∑=

ym is the mean of logs (peak annual flood)

N is the length of record

2

1

2

1

)(

−

−= ∑

N

yy m

yσ

yσ is the standard deviation of the logs

( ) ( )∑

−−−

=3

21 y

m

k

yy

NN

NS

σ

kS is the coefficient of skew of the logs


4-19

Using these three parameters, the magnitude of the flood of the desired frequency can be

determined from the equation,

yTmT Kyy σ*+=

Ty = log Q = the logarithm of the flood magnitude.

TK = a frequency factor for a particular return period and coefficient of skew

If the skew of the sample data happens to be equal to zero, the plot of the log-Pearson fit to

the data will be a straight line.

If the skew is negative the plot will be a curve with a downward concavity.

If the skew is positive, the plot will be a curve with upward concavity.

The resulting skew from the analysis is found to be negative and the the characteristics of

the curve conforms to downward concavity. The results are shown below :

Return Period in years

Flood (m

3/sec)

2 1547

5 2041

10 2336

25 2678

50 2915

100 3138

200 3455

500 3618

1000 3814

Based on the Chi-square test results the Log Pearson type-III distribution results are

adopted.

The detail computations are shown in Annexure 4-9

2) Analysis of exceedances

The analysis of exceedance is based on the assumption of thereshold value selected from

the full series of data in such a way that the number of values above the threshold equals the

number of years of data. The flood value referring to this exceedance is termed as, Xexc.

The relationship between the above two methods is shown by Langbein (Chow, 1964) and

the expression for the same is,

−

−= pT

T

1

exp11

where, T is the return period of annual extremes and pTis the return period for the partial

duration series.


4-20

The computations for XT and Xexc have been shown for each station in Annexure 4-9 which

also includes results of analysis of exceedance.

4.6.4 Unit Hydrograph Approach

The unit hydrograph approach is dependent on rainfall uniformly covering the catchment

area, and the area for which this is applicable is normally constrained by this consideration.

Areal rainfall during the Indian monsoon can be widespread and can be fairly uniform over

quite large areas. However, where there are large variations in elevation such as in mountain

areas, rainfall will inevitably vary because of orographic effects at different elevations. In this

case, the snow-bound upper catchment adds to the mountain complication when considering

the use of a unit hydrograph approach.

For the synthetic unit hydrograph, hydrometeorological approach is adopted for developing a

regional method for estimating design flood for small and medium catchments in various

hydrometeorologically homogenous sub-zones. In this approach, the effective rainfall is the

input derived from design storm and then it is applied to the unit hydrograph as a transfer

function to obtain the design flood as output.

Well-researched estimates of storm rainfall intensities for critical durations are needed for the

unit hydrograph approach, and these are likely to be available for much of India. However,

catchment storm loss rates are usually difficult to determine without onerous analysis of a

good network of raingauges together with a lengthy and accurate flood record at the site of

interest. Cumulative uncertainties in storm cell characteristics, catchment losses and pre-

storm catchment state all add to overall limitations in the confidence with which this approach

can be used to derive standard return period floods. In recognition of this fact, flood

hydrographs in countries such as the UK use flood peak frequency analysis to scale back

UH-derived design flood hydrographs.

The synthetic unit hydrograph in the present study is a unit hydrograph of unit duration for

the studied catchment of Alaknanda. The analysis to obtain the synthetic unit hydrograph is

described in three phases below:

• Physiographic parameters of the catchment

• Derivation of 1-hour Unit hydrograph

• Estimation of flood


4-21

U.G = Unit Hydrograph

Tr = Unit rainfall duration adopted in a specific study (hours)

Tm = Time from the start of rise to the peak of the U.G.(hours)

tp = Time from centre of the effective rainfall duration to U.G. peak (hours)

Qp = Peak discharge of unit hydrograph (cumecs)

W50 = Width of U.G. measured at 50% of the peak discharge ordinate (hour)

W75 = Width of U.G. measured at 75% of the peak discharge ordinate (hour)

WR50 = Width of rising limb of U.G. measured at 50% of the peak discharge ordinate (hour)

WR75 = Width of rising limb of U.G. measured at 75% of the peak discharge ordinate (hour)

TB = Base width of U.G (hours)

qp = Discharge per unit area ,Qp /A (cumecs/sq.km)

a) Physiographic parameters of the catchment

Catchment Area (A):

The toposheet is digitised for the desired catchment with gauging site is located watershed

boundary duly marked on it. The area enclosed in this boundary is measured.

Length of the Main Stream (L):


4-22

This implies the longest length of the main river from the farthest. watershed boundary of the

catchment area to the gauging site. The centre of gravity of the catchment is found out by

graphical method for closed polygon. The stream may or may not pass through the centre of

gravity but the nearest point to the centre of gravity is considered to find the length of the

main river from the centre of gravity to the point of study (Lc).

Equivalent Stream Slope (S):

One of the physiographical parameters is slope. The slope may be equivalent slope or

statistical slope. In this report equivalent stream slope has been used for developing SUG

relations.

The L section is broadly divided into segments representing broad ranges of the slopes of

the segments. Following formula is used to compute equivalent slope (S).

2

)1( )(

L

DDLS

iii∑ += −

Elevations of river bed at intersection points of contours reckoned from the bed elevation at

points of interest considered as datum and D (i-1) and Di are the heights of successive bed

location at contour arid intersections. Details of catchment plan and elevation are shown in

Figure 4-9 below.

b) Derivation of 1-hour Unit hydrograph

The empirical relation for unit hydrograph derivation is referred from [4] and the same

formulae are listed below:

The 1-hour unit graph is obtained from the above parameters and is convoluted to obtain the

flood peaks and total flood for various return periods applying the storm depth corresponding

to the return period. The 50 and 100 years 24 hours rainfall depths are adopted from Flood

estimation report, Zone-7, CWC.

The design storm study of Vishnugad Pipalkoti H.E. project was carried out by Indian

Meteorological Department, New Delhi and SPS hyetograph maps for 1-day, 2-day and 3-

day SPS have been depicted in the report. In the present study, since the base perios of unit

hydrograph is less than 24-hours, the 1-Day SPS value is referred from the report .The

tp = 2.498*(L*Lc/S)^0.156

qp = 1.048*tp^-0.178

W50 = 1.954*(L*Lc/S)^0.099

W75 = 0.972*(L*Lc/S)^0.124

WR50 = 0.189*(W50)^1.769

WR75 = 0.419*(W75)^1.246

TB = 7.845*tp^0.453

Tm = tp+0.5

Qp = qp*A

TD = 1.1*tp


4-23

catchment area is superimposed over the catchment drawn for Vishnugad Pipalkoti H E

Project and 1-day SPS value is estimated as 15.6 cm and the same is adopted for computing

SPF.

The moisture adjustment factor, MAF for the zone is estimated as 1.57 by IMD for Vishnugad

Pipalkoti H.E. project and the same value is adopted for BNP to estimte the PMP.The

adopted value of PMP is 24.5 cm

Design Loss Rate:

As recommended in the CWC report, the design loss has been adopted as 0.5 cm/hr.The

base flow and snowmelt contribution are adopted @ 0.05 Cumec/SqKm (rainfed area).As a

result, the base flow estimated is 143 cumecs and 180 cumec is the considered snowmelt

contribution added to the base flow to compute the total flood.


4-24

Figure 4-8: Catchment Area Characteristics


4-25

c) Estimation of flood.

The effective rainfall for design storm duration is to be applied to the unit hydrograph of a

catchment to obtain the design flood of required return period. The procedure for computing

design flood peak and design flood hydrograph for T year returns period by synthetic unit

hydrograph approach is as under :

d) Computation of design flood peak

Flood peaks of 50 and 100 years return period have been computed with a prior analysis of

24 hours rainfall for the corresponding return periods duly obtained from the isopluvial lines

as given in Plate-9 and Plate-10 for 50 and 100 years respectively. Detailed steps for flood

peak estimation are followed using [4]. The SPF and PMF hydrographs are generated using

SPS and PMP respectively. The PMP values are referred from 1-day PMP atlas, IMD, 1988

and the SPS is obtained using the moisture adjustment factor value for the zone reported in

PMP atlas IMD,1988.

The computation of flood by Synthetic Unit Hydrograph equation is attached in Annex 4-10.

4.6.5 Probable Maximum Flood (PMF)

For a catchment of nearly 5,600 km2, design floods of PMF level are best derived from the

enveloping curve of the world maximum observed floods. The latest version of this

publication is “World catalogue of Maximum Observed Floods”, compiled for IASH by Reg

Herschy in 2003 (Ref [2]). It shows that the enveloping world maximum curve, which is

clearly heavily influenced by Indian historic floods, has the simplified formula of:

Q = 500A0.43

m3/s, where A is the catchment area in km

2, and this has the Francou index, k,

of approximately 6.

For the 2,850 km2 rain-fed catchment area at Bowala Nand Prayag, this formula results in a

PMF of 15,300 m3/s.

The PMF is also estimated from the PMP storm in Annex 4-10 by synthetic unit hydrograph

method. This estimate gives a figure of 17,400 m3/s which corresponds reasonably well with

the value above derived from the enveloping curve.

4.6.6 Summary of Flood Analysis

Table 4-2 Summary of Flood Analysis

Flood Based on

Enveloping

Curve

Based on

Flood Frequency

Analysis

Based on

Unit Hydrograph

PMF 15,300 17367

SPF 9780

500 year 3,930

100 year 3,240 8709

50 year 2,950 5335


4-26

Given the relatively short length of record for annual flood peaks it is considered that the

flood peaks estimated by flood frequency analysis are not reliable and it is proposed to adopt

the more conservative values for flood peaks given by the unit hydrograph method for the

design of Bowala Nand Prayag HEP. This gives the following values, as compared with the

values proposed in the 1992 DPR:

Annual Flood Peak for return periods (m3/s)

50 years 100 years 500 years 1000 years

Present Study 7,210 8,240 10,630

1992 DPR 7,041 8,207 9,610

4.7 Design Discharge

4.7.1 Design Discharge for Barrage

According to the CWC ‘Manual on Estimation of Design Flood’, for weirs and barrages, which

are diversion structures having small storage capacities, the risk of loss of life and property

down stream would rarely be increased by failure of the structure. Apart from the damage to

the structure itself the failure would cause disruption of water supply to the power station.

Existing practice for design of barrages and weirs is based on BIS Code, IS 6966 (Part I),

1989: “Hydraulic Design of Barrages and Weirs”. For purposes of design of items other, than

free board, a design flood of 50- year frequency may normally suffice. In such cases where

risks and hazards are involved, a review of this criteria based on site conditions may be

necessary.

For deciding the free board, a minimum of 500-year frequency flood or the standard project

flood (SPF) may be desirable.

In the case of Bowala Nand Prayag the SPF has the same magnitude as the 500-year flood

and accordingly it is proposed to adopt the 500-year flood for determining the dimensions,

and hence the freeboard, of the barrage. This flood has a magnitude of 10,630m3/s.

4.7.2 Design Discharge for Diversion Works

For construction of the Barrage and Intake structure a working season from 1 October to 31

May is assumed. Over this period, average monthly river flows typically lie in the range 30 –

150 m3/s. Monthly peak discharges at Chamoli for the months of October through March for

the years 1971 to 1981 are available and these have been used in a flood frequency analysis

to determine floods of various return periods during the working season. The results are

given in below


4-27

Figure 4-9: Flood Frequencies during Non-Monsoon

Season

Semi-log Flood Frequencies for Bowala

(Non-Monsoon Period)

5 10 20 50 100

y = 152.23x + 126.06

R2 = 0.8844

0

100

200

300

400

500

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Log Return Period

Flo

w -

m3/s

Return Period

95% Confidence

Upper Boundary

Taking the 95% upper confidence boundary, the non-monsoon floods for various return

periods are:

Return Period (years) 5 10 20 50 100

Flood Discharge (01 Oct – 31 May) 264 314 364 430 481

The design flood for the diversion works is typically taken as the flood of return period 10

times the period for which the temporary works are at risk from flooding. This would suggest

the use of the following design discharges for various construction periods for the Barrage

and Intake Structure:

Construction Period (years) 2 3 4 5

Flood Return Period (years) 20 30 40 50

Design Discharge 364 393 414 430


4-28

4.8 Sediment Studies

4.8.1 Available Data

Daily records of suspended sediment have been obtained from the G&D station at

Rudraprayag on Alaknanda River from June 1994 to May 1998 and from the G&D station at

Nand Prayag on Alaknanda River from March 2007 to May 2008.

4.8.2 Sediment Concentrations

The annual variation in the concentration of suspended sediment is presented in Figure 4-10

and the variation in the concentration of suspended sediment as a function of the river flow is

given in Figure 4-11. The amount of suspended sediment is dependent on a number of

factors including the rate of erosion in the catchment area, landslips which can deposit large

volumes of material into the river channel and human activities. Consequently the amount of

suspended sediment is highly variable.

4.8.3 Petrographic Analysis

Petrographic analyses of samples of suspended sediments have been carried out by GSI

Laboratory in Faridabad giving the following composition:

Due to the high quartz content the sediments in the Alaknanda River will be highly abrasive,

so it is important that the desilting basins operate effectively to remove suspended

sediments. Consideration should also be given to applying a protective coating to the turbine

runners when the specifications are prepared.


4-29

Figure 4-10: Annual Variation in Suspended Sediment at Intake Site

Variation in Suspended Sediment at Intake Site

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

1994 1995 1996 1997 1998

Sed

imen

t (p

pm

)

Figure 4-11: Variation in Suspended Sediment with Discharge

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

0 200 400 600 800 1,000 1,200 1,400 1,600 1,800

Discharge at Intake (m3/s)

Sed

imen

t C

on

cen

trati

on

(p

pm

)


4-30

References

[1] “Hydrological Modelling of Snow & Glacier Covered Basins”. Proc. National Academy of

Science India, special issue 2001

[2] Hughes D. A and V Smatkhin. (1996) “Daily flow time series patching: A spatial interpolation

approach based on flow duration curves”. Hydrological Sciences Journal. Vol 41 (6). pp 852 –

871.

[3] Herschy R . (2003) “World catalogue of Maximum Observed Floods”, IASH

[4] Flood Estimation Report for Western Himalayas- Zone 7, CWC


4-31

Annex 4-1

1971-72 1972-73 1973-74 1974-75 1975-76 1976-77 1977-78 1978-79 1979-80 1980-81 1981-82 1982-83

Jun I 359 192 286 131 196 281 222 391 150 210 217 263II 592 305 592 219 277 344 175 356 249 294 221 354

III 589 372 571 190 315 262 369 516 500 430 335 331Jul I 540 577 626 283 285 480 519 636 442 485 477 445

II 404 630 646 434 390 615 605 528 551 534 572 503

III 455 620 627 536 373 919 564 590 515 539 702 511Aug I 595 573 598 565 386 698 627 703 495 636 807 609

II 498 581 615 513 400 504 551 546 486 412 536 597III 377 515 512 396 344 344 482 548 348 331 378 455

Sep I 262 493 514 298 345 468 387 410 296 265 268 270

II 160 437 363 180 279 294 315 278 166 175 183 221III 119 210 259 135 197 200 239 216 123 141 140 154

Oct I 254 166 170 115 179 172 166 156 86 100 132II 216 116 106 119 147 139 115 121 68 80 95

III 149 95 82 93 101 104 96 102 46 64 76

Nov I 116 83 73 83 81 88 90 76 43 55 68II 74 75 62 73 71 73 68 65 41 54 51

III 76 70 53 66 64 60 56 57 39 46 30Dec I 67 72 50 64 57 52 48 47 36 41 26

II 61 63 44 63 52 49 42 41 32 37 26

III 57 60 40 61 49 47 42 41 29 33 24Jan I 54 56 38 61 45 44 44 40 32 28 25

II 50 55 36 59 43 41 39 39 32 26 23III 48 55 36 60 43 42 35 38 30 26 23

Feb I 49 52 34 62 42 41 34 37 29 25 22

II 48 52 32 64 43 39 34 35 28 24 22III 47 52 30 64 45 39 35 37 31 23 20

Mar I 51 53 32 69 45 40 46 38 33 24 25II 48 57 32 72 44 40 55 40 29 25 28

III 67 74 51 84 48 43 48 43 38 30 43

Apr I 66 80 57 113 54 53 55 67 42 40 65II 74 97 72 104 71 43 129 94 52 83 78

III 68 185 107 131 132 59 119 126 71 87 90May I 128 360 143 142 134 68 211 147 116 133 126

II 98 376 116 203 163 88 282 164 127 149 130

III 213 223 99 180 187 183 314 112 131 204 103

Annex 4-1

Average 10 Daily Discharge Data at Chamoli Site


4-32

Annex 4-2

Page 1/2

Year 1977-78 1978-79 1979-80 1980-81 1981-82 1982-83 1983-84 1984-85 1985-86 1986-87 1987-88 1988-89 1989-90 1990-91 1991-92

Jun I 238.5 328.4 148.9 301.2 355.0 319.0 365.4 512.1 223.6 260.9 356.0 290.0 341.9 378.0 566.7

II 203.8 391.2 235.1 345.7 304.3 482.9 267.8 484.3 291.3 529.5 356.2 282.5 288.5 352.2 663.9

III 432.8 494.5 761.2 707.7 578.3 455.5 427.0 461.2 369.3 772.6 412.6 453.0 360.9 787.8 666.5

Jul I 860.6 998.5 593.3 795.5 643.9 632.5 523.2 643.8 481.8 538.8 599.9 696.9 321.3 948.1 825.9

II 875.5 904.6 759.0 754.4 862.4 756.7 429.6 476.4 720.2 1100.9 526.4 1046.7 681.7 1008.2 821.5

III 954.2 835.3 773.4 882.6 1140.1 800.6 691.1 731.3 651.7 1366.4 1081.4 1225.6 800.0 884.5 1105.0

Aug I 1038.8 718.6 1179.4 1253.4 1334.6 948.2 777.5 596.9 582.5 1172.6 727.3 1269.5 612.5 937.3 1075.8

II 927.8 671.9 1235.3 704.9 1064.8 1082.9 1252.6 692.9 919.6 1161.7 737.1 1249.2 899.5 1155.4 1005.4

III 765.0 1045.8 678.4 678.9 707.6 825.9 818.8 664.7 800.2 610.4 842.5 914.1 1145.9 909.5 1037.1

Sep I 613.2 947.1 513.0 603.6 434.8 580.6 723.4 711.9 616.9 509.8 725.0 503.5 785.1 789.1 806.9

II 586.1 560.6 299.8 469.8 382.3 272.2 672.4 394.8 477.4 367.0 573.5 361.1 428.4 687.0 628.6

III 411.8 294.4 182.3 441.7 388.9 334.2 548.6 291.5 420.9 306.6 331.1 386.8 314.6 457.6 464.9

Oct I 244.7 239.5 211.3 304.6 323.6 237.3 338.4 218.5 334.4 225.4 202.7 268.3 242.5 290.6 362.1

II 227.7 208.6 198.4 229.6 299.9 201.5 281.2 155.9 432.7 191.2 147.9 206.6 202.6 229.5 260.8

III 182.3 162.9 174.5 343.5 280.2 174.2 222.5 150.9 279.1 141.2 116.8 180.4 176.7 167.5 197.9

Nov I 157.0 138.0 159.9 199.2 282.4 149.8 166.1 114.5 212.4 117.7 99.8 157.2 153.6 152.4 163.4

II 145.4 141.4 128.4 179.5 190.5 126.8 133.5 107.7 160.6 112.1 90.5 138.1 135.7 143.2 143.5

III 121.0 155.7 105.0 127.1 95.9 110.8 111.6 102.2 132.5 102.2 81.1 121.4 121.7 136.9 126.4

Dec I 117.8 138.0 96.7 108.0 91.4 99.9 106.0 94.4 128.4 96.8 70.0 109.5 113.0 124.9 116.5

II 106.3 100.0 76.5 99.6 90.6 90.4 99.4 83.5 114.4 94.6 73.8 99.8 101.1 113.1 109.0

III 99.4 94.7 72.8 99.0 92.9 90.5 92.3 80.0 112.2 94.2 68.8 98.9 99.3 109.5 110.7

Jan I 96.9 87.9 74.2 95.7 85.1 86.3 88.0 90.3 108.9 87.3 62.7 111.6 94.3 121.2 107.7

II 84.7 86.1 68.6 99.5 73.4 81.5 83.9 75.0 102.4 86.4 60.3 101.1 90.8 109.4 110.2

III 78.7 81.6 65.0 102.6 79.9 84.3 79.6 70.1 89.1 73.2 53.9 89.1 89.1 103.3 108.8

Feb I 77.0 67.5 67.0 99.9 77.1 80.8 76.4 69.3 82.9 72.1 50.5 84.1 87.5 97.1 107.6

II 86.0 61.9 63.5 98.1 81.1 77.7 72.1 64.8 82.1 76.8 52.8 79.0 91.5 98.9 96.1

III 86.7 89.0 60.9 101.3 76.8 75.2 76.6 68.1 82.6 74.4 55.8 73.0 88.5 95.1 92.0

Mar I 99.2 91.7 76.6 109.0 101.8 80.4 75.2 74.5 72.8 70.6 67.8 75.9 95.9 108.0 93.6

II 202.1 84.5 57.8 108.1 111.3 84.5 84.2 68.4 90.7 72.5 117.8 74.6 97.2 115.7 100.4

III 131.2 98.1 72.6 115.6 144.8 101.8 97.6 79.0 100.6 82.1 93.2 86.1 132.2 128.9 116.0

Apr I 136.3 109.7 88.7 113.7 168.6 107.7 85.8 81.1 95.6 104.9 92.7 94.2 118.8 146.2 114.1

II 198.0 113.6 117.1 191.5 167.4 146.6 97.0 105.1 133.6 102.0 132.1 97.5 166.7 158.9 131.0

III 155.2 131.5 137.1 201.8 175.7 176.2 114.2 115.1 161.2 136.8 141.9 104.9 194.6 177.5 161.8

May I 167.0 130.8 199.3 240.3 213.2 233.2 181.2 138.2 194.3 185.9 190.9 124.4 197.0 221.3 185.4

II 239.4 185.9 178.3 270.1 205.8 267.9 236.5 163.0 280.7 149.6 279.8 206.5 335.1 254.3 286.7

III 257.7 141.8 199.7 331.2 222.3 266.4 324.4 245.3 264.7 229.6 313.2 262.4 349.5 297.4 218.3

Average 10 Daily Discharge Data of Alaknanda at Rudraprayag (CA = 9930km2)


4-33

Annex 4-2

Page 2/2

Year 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99 1999-00 2000-01 2001-02 2002-03 2003-04 2004-05 2005-06 2006-07

Jun I 245.9 340.0 309.3 705.7 380.2 213.3 580.6 307.7 555.6 385.7 450.4 627.2 208.7 215.5 361.7

II 475.1 495.7 356.5 691.2 663.5 314.7 472.6 586.3 701.6 568.6 590.7 747.7 319.5 408.3 268.4

III 632.9 487.3 817.2 402.6 988.2 649.0 1062.9 808.9 832.2 719.7 653.3 803.1 372.8 1056.7 349.4

Jul I 410.6 603.4 1087.2 721.3 586.7 766.7 1348.5 1255.7 857.2 829.9 860.3 1025.4 990.2 1335.2 981.8

II 745.4 1014.9 1029.3 900.2 1223.9 934.0 1280.0 1320.2 1219.2 1338.1 797.3 1159.0 982.6 1427.9 1258.5

III 968.8 777.3 1403.0 1068.9 1233.9 1205.5 1178.3 1502.0 1313.9 1742.7 830.7 1278.8 1025.9 1717.2 1482.5

Aug I 1160.9 818.3 1257.3 1220.5 1356.0 1225.7 1573.3 1674.3 1237.8 1264.4 967.9 1406.3 1675.9 1709.2 1159.4

II 1157.3 709.0 1083.3 926.4 1470.0 916.6 1857.9 1342.1 1351.1 1429.0 937.4 1321.2 1549.3 1214.3 1086.8

III 1215.4 654.4 1482.4 1039.2 1173.6 692.1 1432.0 1173.4 1015.0 1214.9 900.2 1504.5 1209.6 1125.2 1376.8

Sep I 1006.1 960.2 1342.6 1270.6 1054.4 691.9 968.5 944.2 1052.1 756.1 961.8 1261.4 802.1 1099.1 1009.1

II 793.4 812.4 715.1 618.3 637.5 664.9 755.1 960.7 665.5 456.8 1045.8 935.0 613.6 977.5 822.6

III 455.7 399.5 424.9 410.4 447.9 425.8 801.2 726.9 438.9 318.1 304.5 733.8 543.0 1142.2 599.1

Oct I 328.3 280.6 228.1 259.6 392.8 221.2 586.1 488.0 282.8 247.0 179.0 428.0 278.5 646.6 317.7

II 238.8 201.9 174.8 213.2 277.8 182.8 764.8 292.7 230.2 201.9 164.9 380.9 228.7 279.8 257.8

III 195.9 153.7 144.9 166.9 143.9 153.1 558.9 263.0 216.7 169.5 128.1 266.5 184.1 231.2 222.5

Nov I 167.6 122.4 118.1 137.7 122.5 133.1 504.0 211.0 210.3 137.3 96.6 233.6 160.0 204.8 160.8

II 150.6 112.0 97.1 121.7 107.8 122.1 409.2 182.5 194.7 109.5 949.8 167.1 147.2 169.4 146.5

III 134.3 102.7 86.2 101.9 101.1 118.1 343.8 153.1 131.0 104.5 119.8 150.2 132.0 177.5 117.9

Dec I 122.5 91.9 78.3 91.9 91.9 119.1 316.0 131.7 95.7 87.6 117.0 142.1 103.0 149.3 98.5

II 112.1 101.8 71.2 76.6 76.1 118.1 294.7 120.9 87.2 81.1 109.9 130.3 103.6 139.5 93.4

III 104.7 95.9 67.7 72.0 69.6 105.4 260.9 201.9 83.1 77.3 101.3 113.8 92.7 130.6 81.3

Jan I 104.2 87.8 65.3 67.1 65.3 100.5 219.9 98.2 93.6 72.8 94.7 104.8 87.7 124.1 77.4

II 97.2 88.2 61.4 62.6 64.8 91.2 194.6 83.2 115.0 74.6 87.3 98.5 84.2 124.3 70.4

III 87.3 88.3 58.6 62.6 63.3 87.8 180.4 87.7 112.8 71.2 83.0 94.6 88.0 118.7 67.4

Feb I 83.4 83.5 52.0 53.2 59.8 84.2 163.7 93.1 108.8 78.2 83.5 92.5 92.5 112.6 65.8

II 74.5 79.3 59.8 56.0 57.6 82.9 156.6 86.5 107.8 83.4 88.6 90.1 101.3 108.7 72.2

III 76.9 80.3 54.4 63.8 57.2 87.3 148.8 76.4 105.7 83.8 102.0 87.8 93.6 101.7 67.4

Mar I 79.3 79.0 54.0 61.1 56.7 99.2 88.2 77.1 100.2 142.6 116.4 82.3 111.0 90.7 79.5

II 87.0 85.8 52.6 75.6 57.6 103.8 54.2 76.2 96.5 116.3 101.8 89.1 133.1 104.1 123.0

III 109.5 89.4 74.8 89.6 62.0 103.7 61.4 88.7 94.7 112.9 111.1 88.8 120.1 102.5 210.9

Apr I 95.2 104.9 79.2 95.0 79.2 115.0 96.3 114.8 85.1 121.2 125.9 88.4 188.9 105.8 130.6

II 131.4 91.1 76.3 162.5 82.7 151.1 121.5 126.9 90.4 155.1 148.7 95.6 132.9 118.4 162.1

III 205.2 97.1 96.9 220.4 103.1 215.2 182.8 156.9 107.2 178.7 188.4 109.9 174.4 207.5 146.3

May I 305.6 154.6 119.8 280.7 121.6 245.5 285.0 191.8 191.2 244.4 172.3 114.7 216.4 224.1 178.0

II 193.3 152.8 466.4 238.4 109.3 258.8 334.4 396.1 239.3 640.1 253.3 186.4 216.5 310.2 223.9

III 319.2 323.1 203.8 345.6 167.4 642.9 481.2 524.8 228.3 416.1 301.3 211.8 199.2 344.7 271.7

Average 10 Daily Discharge Data of Alaknanda at Rudraprayag (CA = 9930km2)


4-34

Annex 4-3

Page : 1/2

Year 1971-72 1972-73 1973-74 1974-75 1975-76 1976-77 1977-78 1978-79 1979-80 1980-81 1981-82 1982-83 1983-84 1984-85 1985-86 1986-87 1987-88 1988-89

Jun I 259 132 188 150 261 294 203 370 152 309 178 106 235 478 237 176 299 355 II 247 150 299 229 379 233 142 371 311 434 180 201 188 496 286 409 329 304 III 236 169 246 175 466 229 355 486 535 556 287 206 274 447 364 626 363 505 Jul I 225 266 258 229 402 333 550 569 472 572 293 320 353 464 351 502 526 540 II 174 188 258 332 577 478 603 436 565 641 354 348 324 373 432 572 476 632 III 251 193 268 392 502 573 546 512 517 667 415 350 515 458 418 698 634 709 Aug I 252 217 242 367 528 535 592 599 502 620 389 400 533 453 409 587 518 622 II 239 200 262 338 553 411 474 412 481 431 347 358 624 500 453 592 474 544 III 212 204 229 269 503 383 398 429 381 379 227 286 548 473 449 419 528 454 Sep I 177 298 215 230 418 397 376 337 341 300 180 157 438 389 350 375 434 351 II 137 298 212 189 325 300 242 240 185 153 173 127 349 292 268 256 339 232 III 122 171 211 170 217 182 172 233 114 122 129 78 239 145 211 214 285 237 Oct I 114 139 133 140 183 140 107 159 124 106 81 52 123 12 175 148 155 132 II 110 158 89 135 150 102 88 109 96 80 66 39 99 88 151 127 101 117 III 87 117 75 95 116 87 84 107 68 66 54 33 70 88 103 97 81 114 Nov I 88 104 68 76 92 76 78 83 62 56 42 29 55 64 80 85 73 100 II 61 88 72 68 76 69 62 63 52 48 35 26 49 54 65 75 64 85 III 50 74 62 60 70 64 55 75 45 40 30 22 43 46 55 63 56 71 Dec I 45 68 55 53 68 60 49 63 41 33 21 21 37 36 49 56 52 59 II 43 68 56 46 57 53 42 56 36 28 18 20 37 34 44 52 50 46 III 41 53 53 41 47 47 36 56 34 26 16 18 36 31 40 51 47 40 Jan I 43 47 46 39 42 41 36 45 33 27 15 17 36 31 40 49 45 34 II 44 44 41 37 35 40 34 42 32 24 13 16 36 28 38 48 44 30 III 39 40 43 38 32 39 33 40 31 26 14 16 34 33 37 46 40 31 Feb I 36 37 40 41 32 36 32 39 29 25 14 16 33 27 35 45 37 39 II 38 36 39 39 33 35 30 37 30 28 15 16 31 27 35 44 34 35 III 35 37 36 39 33 39 33 38 27 33 14 16 32 29 34 44 37 35 Mar I 35 35 41 42 35 41 36 38 28 29 17 18 37 34 34 43 44 38 II 36 40 45 44 35 42 39 42 27 32 16 20 35 33 36 44 56 40 III 43 45 52 56 41 49 39 51 30 36 22 23 46 39 36 47 58 42 Apr I 48 53 63 84 47 55 42 63 37 39 35 28 40 38 40 55 66 54 II 61 61 70 83 59 47 86 88 43 35 47 33 48 59 59 55 103 58 III 64 109 93 125 114 56 89 123 63 51 59 35 57 73 81 80 121 62 May I 75 212 156 141 122 62 153 142 151 116 67 48 117 94 131 83 157 69 II 131 154 137 224 170 86 268 170 175 127 67 113 235 119 240 80 211 146 III 163 136 115 213 208 111 315 122 217 166 77 116 345 246 149 111 328 219

Average 10 Daily Discharge Data at Joshimath Site (CA =4508 km²)


4-35

Annex 4-3

Page : 2/2

Year 1989-90 1990-91 1991-92 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99 1999-00 2000-01 2001-02 2002-03 2003-04 2004-05 2005-06 2006-07

Jun I 284 364 351 186 269 284 301 311 158 427 180 352 351 293 379 165 144 269 II 247 311 409 326 372 294 493 481 189 397 335 419 436 357 387 199 240 151 III 283 503 437 345 321 422 205 625 344 875 477 406 504 456 386 214 515 199 Jul I 294 474 526 283 379 439 370 400 389 1158 459 375 691 570 406 322 508 371 II 438 508 467 373 425 456 503 579 471 1262 444 461 715 576 411 282 554 443 III 540 410 533 423 356 544 516 594 569 1200 417 444 738 503 478 317 542 418 Aug I 339 422 417 432 400 415 582 607 391 1188 415 191 625 499 514 435 600 293 II 370 428 362 401 353 361 366 618 341 1084 390 132 570 344 517 507 461 251 III 445 355 338 372 342 375 371 423 263 1154 319 137 440 290 504 407 376 258 Sep I 297 352 319 345 299 337 377 400 280 1068 249 135 317 268 485 343 384 128 II 212 274 252 306 244 215 236 285 216 1003 248 78 236 224 427 343 307 117 III 174 233 192 205 177 148 174 213 143 1012 232 31 152 140 346 293 251 91 Oct I 116 170 165 181 132 123 137 138 94 898 141 21 95 106 216 256 172 85 II 88 149 140 136 104 94 103 103 78 847 84 39 69 107 183 245 138 70 III 79 113 104 121 91 76 66 76 67 912 73 15 45 111 171 193 100 57 Nov I 64 89 95 104 63 49 53 60 57 852 59 70 41 92 108 167 91 44 II 53 78 68 92 46 36 48 46 47 496 52 50 37 85 101 154 81 42 III 45 66 63 84 39 27 37 38 43 386 47 32 31 76 91 137 75 37 Dec I 40 49 59 74 36 25 29 35 41 377 51 24 28 67 82 117 64 34 II 38 41 49 66 29 22 26 31 38 369 67 22 26 59 72 100 53 32 III 33 38 44 58 26 39 23 27 36 168 60 21 25 55 64 92 43 31 Jan I 31 35 42 54 25 17 20 24 33 54 55 13 27 51 60 90 35 28 II 29 33 37 51 22 16 18 22 36 50 54 9 32 51 55 89 33 25 III 29 30 34 47 20 17 18 21 33 47 54 8 32 52 50 78 36 24 Feb I 28 30 29 46 19 16 16 19 34 42 57 10 32 52 52 78 33 23 II 28 30 30 50 19 16 15 18 33 42 53 9 31 52 53 84 33 24 III 27 29 27 46 20 16 18 18 31 41 55 10 34 58 54 88 33 24 Mar I 29 31 31 44 19 16 18 16 36 43 55 15 24 56 41 85 33 24 II 31 38 38 46 22 17 26 18 40 43 53 13 46 55 46 83 27 26 III 35 47 42 49 26 23 40 18 41 44 54 22 60 59 51 77 30 37 Apr I 39 49 65 52 36 20 39 22 61 53 82 19 69 78 53 91 37 47 II 68 56 45 76 38 25 81 26 72 72 89 33 86 106 55 85 46 50 III 109 99 103 150 36 53 109 51 143 161 110 66 103 140 64 83 43 57 May I 116 153 120 224 94 85 143 63 158 186 183 117 112 158 56 94 89 89 II 272 210 184 140 102 199 153 48 182 182 297 282 161 229 74 94 118 132 III 309 278 168 233 273 165 251 104 413 279 368 239 222 299 132 98 179 150

Average 10 Daily Discharge Data at Joshimath Site (CA =4508 km²)


4-36

2850 km2

2740 km2

5590 km2

0.00575 m/ 0C/ Day

Lowest

Elevation

of

snowmelt

Elevation

where

snowmelt

stops

Average

temperature of

area between

Elevation

(a) and (b)

Snowmelt

areaSnowmelt Snowmelt

(a) (b) Corresponding to (a) Corresponding to (b) (0C) (km

2) (m

3) (mm)

June 4000 5273 6.73 0 3.36 1138.75 660986696 241.236

July 4000 5133 6.28 0 3.14 974.23 527889298 192.660

Aug 4000 5067 5.98 0 2.99 900.33 464294199 169.450

Sep 4000 4878 4.59 0 2.29 701.94 277638893 101.328

Oct 3900 4395 2.23 0 1.11 336.93 64679903 23.606

Nov 3200 3765 3.23 0 1.61 273.36 76058333 27.759

Dec 2800 3328 2.63 0 1.31 216.47 49026007 17.893

Jan 2600 3018 1.77 0 0.89 160.82 24551798 8.961

Feb 2800 3218 1.38 0 0.69 168.46 20021787 7.307

Mar 3400 3848 2.05 0 1.03 231.4 40925743 14.936

Apr 3950 4548 2.55 0 1.28 430.49 94840665 34.613

May 4000 4939 4.74 0 2.37 764.39 312476458 114.043

Mean

Temparature ( 0C )

at Elevation Month

Computation of snowmelt contribution : BNP

Rainfed catchment area =

Snowfed catchment area =

Total catchment area =

Degree day factor =


4-37

2850 km2

2740 km2

5590 km2

0.00575 m/ 0C/ Day

Discharge

at Joshimath

Volume

of

flow

Snowmelt

Flow

contributed

by rainfed

area

Flow

contributed

by rainfed

area

(m 3 /sec) (m 3 ) (m 3 ) (m 3 ) (mm)

June 346 896991604 660986696 236004908 82.809

July 550 1424472361 527889298 896583064 314.591

Aug 534 1384150675 464294199 919856477 322.757

Sep 294 762824309 277638893 485185416 170.240

Oct 131 340723447 64679903 276043544 96.857

Nov 72 186901815 76058333 110843482 38.892

Dec 49 127744504 49026007 78718497 27.621

Jan 36 94247071 24551798 69695274 24.454

Feb 33 86566155 20021787 66544368 23.349

Mar 40 102846250 40925743 61920508 21.726

Apr 73 188727851 94840665 93887186 32.943

May 174 450574875 312476458 138098418 48.456

1204.695

Month

Flow contributed by rainfed area




Degree day factor =


4-38

2850 km2

2740 km2

5590 km2

0.00575 m/ 0C/ Day

Discharge

at

Joshimath

Volume

of

flow

Total

RunoffSnowmelt

Flow

contributed by

rainfed area

Flow

contributed by

rainfed area

(m3/sec) (m

3) (mm) (m

3) (m

3) (mm)

June 346 896991604 160.464 660986696 236004908 82.809 0.263

July 550 1424472361 254.825 527889298 896583064 314.591 0.629

Aug 534 1384150675 247.612 464294199 919856477 322.757 0.665

Sep 294 762824309 136.462 277638893 485185416 170.240 0.636

Oct 131 340723447 60.952 64679903 276043544 96.857 0.810

Nov 72 186901815 33.435 76058333 110843482 38.892 0.593

Dec 49 127744504 22.852 49026007 78718497 27.621 0.616

Jan 36 94247071 16.860 24551798 69695274 24.454 0.739

Feb 33 86566155 15.486 20021787 66544368 23.349 0.769

Mar 40 102846250 18.398 40925743 61920508 21.726 0.602

Apr 73 188727851 33.762 94840665 93887186 32.943 0.497

May 174 450574875 80.604 312476458 138098418 48.456 0.306

1204.695

Monthly flow ratio : [ Qrainfed/Qtotal ]

Ratio

(FlowArainfed/

Total Flow)

Month




Degree day factor =


4-39

YearsMonsoon

Rainfall

(mm)

Monsoon

Runoff

(mm)

Runoff Factor

1971 979.500 377.852 0.39

1972 779.600 422.151 0.54

1973 737.400 477.162 0.65

1974 655.900 301.618 0.46

1975 681.200 305.993 0.45

1976 510.100 424.367 0.83

1977 700.000 379.441 0.54

1978 664.200 420.882 0.63

1979 289.800 365.390 1.26

1980 488.700 396.849 0.81

1981 335.500 374.072 1.11

1982 641.500 325.214 0.51

1983 787.900 377.667 0.48

1984 453.100 366.650 0.81

1985 537.000 350.607 0.65

1986 504.200 424.620 0.84

1987 728.000 384.270 0.53

1988 364.200 426.558 1.17

1989 603.100 350.375 0.58

1990 426.825 -

1991 437.026 -

1992 402.775 -

1993 674.800 374.635 0.56

1994 185.700 458.535 2.47

1995 694.300 435.906 0.63

1996 656.000 491.033 0.75

1997 379.600 382.523 1.01

1998 343.000 721.790 2.10

1999 749.000 489.197 0.65

2000 755.000 434.669 0.58

2001 621.000 498.675 0.80

2002 635.000 395.268 0.62

Rainfall-Runoff excluding snowmelt for Monsoon : BNP


4-40

The number of crests and troughs in the data series of peak Discharge determines the randomness of the same.

using the method below :

Let Qt be the peak annualDischarge to be counted as crest or trough

Years Rt Score

21

1971-72 589.05 -

1972-73 623.70 - 0 32

1973-74 639.54 - 1

1974-75 559.35 - 0 For N = 32 (2/3)*(N-2) = 20.00

1975-76 396.00 - 1

1976-77 909.81 - 1 (16N-α)/90 = 5.45556

1977-78 620.73 - 1

1978-79 695.97 - 1 σ = 2.336

1979-80 545.49 - 1

1980-81 629.64 - 0 (α-Mean)/σ = 0.428 <<< 1.96

1981-82 798.93 - 1

1982-83 602.91 - 0 less than 1.96 the series is random

1983-84 592.08 - 0

1984-85 525.48 - 0

1985-86 515.07 - 1

1986-87 748.67 - 1

1987-88 643.85 - 1

1988-89 694.70 - 1

1989-90 556.26 - 1

1990-91 570.06 - 0

1991-92 620.53 - 1

1992-93 592.91 - 0

1993-94 550.65 - 1

1994-95 710.77 - 1

1995-96 639.83 - 1

1996-97 688.36 - 1

1997-98 645.89 - 1

1998-99 892.94 - 1

1999-00 697.51 - 0

2000-01 641.35 - 1

2001-02 862.12 - 1

2002-03 588.00 - 021

32

(Value corresponding to 5% probability)

Total number of crest and troughs, α =

Total number of data, N =

Variance =

Standard deviation =

Normal variate =

Mean =

Total Score, αααα =

N =

Test for Randomness : BNP

Since the normal deviate is

Qt is crest when

Qt is trough when

Qt-1 < Qt > Qt+1

Qt-1 > Qt < Qt+1

Observed rank Sorted Rank

Kx Ky

1971-72 589.050 10 909.810 1 81

1972-73 623.700 16 892.938 2 196 p = P(t < tp) � 0.025 0.975

1973-74 639.540 18 862.122 3 225 df

1974-75 559.350 7 798.930 4 9 4 -2.78 2.78

1975-76 396.000 1 748.667 5 16 5 -2.57 2.57

1976-77 909.810 32 710.771 6 676 6 -2.54 2.54

1977-78 620.730 15 697.514 7 64 7 -2.36 2.36

1978-79 695.970 25 695.970 8 289 8 -2.31 2.31

1979-80 545.490 4 694.703 9 25 9 -2.26 2.26

1980-81 629.640 17 688.363 10 49 10 -2.23 2.23

1981-82 798.930 29 645.886 11 324 11 -2.20 2.20

1982-83 602.910 13 643.852 12 1 12 -2.18 2.18

1983-84 592.077 11 641.351 13 4 14 -2.14 2.14

1984-85 525.483 3 639.826 14 121 16 -2.12 2.12

1985-86 515.073 2 639.540 15 169 18 -2.10 2.10

1986-87 748.667 28 629.640 16 144 20 -2.09 2.09

1987-88 643.852 21 623.700 17 16 24 -2.06 2.06

1988-89 694.703 24 620.730 18 36 30 -2.04 2.04

1989-90 556.264 6 620.525 19 169 40 -2.02 2.02

1990-91 570.065 8 602.910 20 144 60 -2.00 2.00

1991-92 620.525 14 592.906 21 49 100 -1.98 1.98

1992-93 592.906 12 592.077 22 100 160 -1.97 1.97

1993-94 550.646 5 589.050 23 324 -1.96 1.96

1994-95 710.771 27 588.002 24 9

1995-96 639.826 19 570.065 25 36

1996-97 688.363 23 559.350 26 9

1997-98 645.886 22 556.264 27 25

1998-99 892.938 31 550.646 28 9

1999-00 697.514 26 545.490 29 9

2000-01 641.351 20 525.483 30 100

2001-02 862.122 30 515.073 31 1

2002-03 588.002 9 396.000 32 529

Avg 643.380

n = 32 ΣΣΣΣ D2

= 3958

Rsp = 0.274560117

Test Statistic t = 1.564 30

Since t = 1.564 lies in the range [-2.04,+2.04] for df = 30, there is no trend in the series.

Student t-distribution

Percentile points of student t-distribution for

significance level (α = 5%) or 95% confidence level

Note : For any missing value in the list of df, the next higher value is adopted.

Spearman's test for absence of trend : BNP

Spearman's coefficient of rank correlation

for degree of freedom, df = (n-2) =

Years Peak Discharge BNP Sorted

Peak DischargeD

2 = (Kx-Ky)

2


4-41

Rp(log)Avg = 6.5

1971-72 589.050 6.379

1972-73 623.700 6.436 σσσσRp(log) = 0.169

1973-74 639.540 6.461

1974-75 559.350 6.327 Sk = 0.017

1975-76 396.000 5.981

1976-77 909.810 6.813 n = 32

1977-78 620.730 6.431

1978-79 695.970 6.545

1979-80 545.490 6.302

1980-81 629.640 6.445

1981-82 798.930 6.683

1982-83 602.910 6.402

1983-84 592.077 6.384

1984-85 525.483 6.264

1985-86 515.073 6.2441986-87 748.667 6.618 Olow = = 410.030 mm

1987-88 643.852 6.4671988-89 694.703 6.543 Ohigh = = 982.044 mm

1989-90 556.264 6.321

1990-91 570.065 6.346 Kn = 2.591

1991-92 620.525 6.431

1992-93 592.906 6.385

1993-94 550.646 6.311

1994-95 710.771 6.566

1995-96 639.826 6.461

1996-97 688.363 6.534

1997-98 645.886 6.471

1998-99 892.938 6.795

1999-00 697.514 6.548

2000-01 641.351 6.464

2001-02 862.122 6.759

2002-03 588.002 6.377

Average = 6.453

St.Dev = 0.169

Skewness = 0.017

Kn is the outlier test values for 10% significance level for a Normal distribution

High outlier threshold = exp[ Rp(log)Avg +Kn * σσσσRp(log) ]

Mean of log transformed annual peak Discharge=

Low outlier threshold = exp[ Rp(log)Avg - Kn * σσσσRp(log) ]

Check for ouliers

Threshold for ouliers

If -0.4 < Sk < +0.4 then, check for High outliers first

If Sk > +0.4 then, check for High outliers first

If Sk < -0.4 then,check for Low outliers first

Standard Deviation of Rp(log) series =

Skewness Coefficients of Logs =

Number of years =

Test for Outliers : BNP

Log Transformed

Peak Discharge_BNP Peak Discharge BNP


4-42

Rpeak_BNP 1 F-Test Two-Sample for Variances

1971-72 589.050

1972-73 623.700 Rpeak_BNP 1 Rpeak_BNP 2

1973-74 639.540 Mean 624.526238 662.2333584

1974-75 559.350 Variance 14658.16585 9619.584216

1975-76 396.000 Observations 16 16

1976-77 909.810 df 15 15

1977-78 620.730 F 1.523783723

1978-79 695.970 P(F<=f) one-tail 0.212062047

1979-80 545.490 F Critical one-tail 2.403447072

1980-81 629.640

1981-82 798.930

1982-83 602.910

1983-84 592.077

1984-85 525.483 t-Test: Two-Sample Assuming Unequal Variances

1985-86 515.073


Rpeak_BNP 2 Mean 624.526238 662.2333584

1987-88 643.852 Variance 14658.16585 9619.584216

1988-89 694.703 Observations 16 16

1989-90 556.264 Hypothesized Mean Difference 0

1990-91 570.065 df 29

1991-92 620.525 t Stat -0.968008433

1992-93 592.906 P(T<=t) one-tail 0.170522234

1993-94 550.646 t Critical one-tail 1.699126996

1994-95 710.771 P(T<=t) two-tail 0.341044468

1995-96 639.826 t Critical two-tail 2.045229611

1996-97 688.363

1997-98 645.886

1998-99 892.938

1999-00 697.514

2000-01 641.351

2001-02 862.122

2002-03 588.002

p = P(t < tp) � 0.025 0.975

df

4 -2.78 2.78

5 -2.57 2.57

6 -2.54 2.54

7 -2.36 2.36

8 -2.31 2.31

9 -2.26 2.26

10 -2.23 2.23

11 -2.20 2.20

12 -2.18 2.18

14 -2.14 2.14

16 -2.12 2.12

18 -2.10 2.10

20 -2.09 2.09

24 -2.06 2.06

30 -2.04 2.04

40 -2.02 2.02

60 -2.00 2.00

100 -1.98 1.98

160 -1.97 1.97

-1.96 1.96

Note : For any missing value in the list of df, the next higher value is adopted.

F-Test (Stability of Variance) & t-Test (Stability of Mean) : BNP

Student t-distribution

Percentile points of student t-distribution for

significance level (α = 5%) or 95% confidence level

First series of peak rainfall for F-Test & t-Test : Barmer

0

100

200

300

400

500

600

700

800

900

1000

1971-72 1972-73 1973-74 1974-75 1975-76 1976-77 1977-78 1978-79 1979-80 1980-81 1981-82 1982-83 1983-84 1984-85 1985-86 1986-87

Peak R

ain

fall (

mm

)Rpeak_BNP 1

Second series of peak rainfall for F-Test & t-Test : Barmer

0

100

200

300

400

500

600

700

800

900

1000

1987-88 1988-89 1989-90 1990-91 1991-92 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99 1999-00 2000-01 2001-02 2002-03

Peak R

ain

fall (

mm

)

Rpeak_BNP 2


4-43

F-Test Two-Sample for VariancesRpeak_BNP 1


1972-73 623.700 Mean 605.5073206 662.2333584

1973-74 639.540 Variance 9504.276751 9619.584216

1974-75 559.350 Observations 15 16

1975-76 396.000 df 14 15

1977-78 620.730 F 0.988013259

1978-79 695.970 P(F<=f) one-tail 0.4934357481979-80 545.490 F Critical one-tail 0.40600842

1980-81 629.640

1981-82 798.930

1982-83 602.910 t-Test: Two-Sample Assuming Unequal Variances1983-84 592.077


1985-86 515.073 Mean 605.5073206 662.2333584

1986-87 748.667 Variance 9504.276751 9619.584216

Rpeak_BNP 2 Observations 15 16

1987-88 643.852 Hypothesized Mean Difference 0

1988-89 694.703 df 29

1989-90 556.264 t Stat -1.614271847

1990-91 570.065 P(T<=t) one-tail 0.058649159

1991-92 620.525 t Critical one-tail 1.699126996

1992-93 592.906 P(T<=t) two-tail 0.1172983181993-94 550.646 t Critical two-tail 2.045229611

1994-95 710.771

1995-96 639.826

1996-97 688.363

1997-98 645.886

1998-99 892.938

1999-00 697.514

2000-01 641.351

2001-02 862.122

2002-03 588.002

Peak Discharge excluding 1976-77

First series of peak rainfall excluding 1990 for F-Test & t-Test : Barmer

0

100

200

300

400

500

600

700

800

900

1971-72 1972-73 1973-74 1974-75 1975-76 1977-78 1978-79 1979-80 1980-81 1981-82 1982-83 1983-84 1984-85 1985-86 1986-87

Pea

k R

ain

fall

(m

m)

Rpeak_BNP 1

First series of peak rainfall excluding 1990 for F-Test & t-Test : Barmer

0

100

200

300

400

500

600

700

800

900

1000

1987-88 1988-89 1989-90 1990-91 1991-92 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99 1999-00 2000-01 2001-02 2002-03

Pe

ak

Rain

fall (

mm

)

Rpeak_BNP 2


4-44

Annex 4-4: Data Consistency Check

a) Regression Analysis

i) Joshimath v Rudraprayag

Discharge data (1977-2002)

y = 0.2453x1.1139

R2 = 0.8421

0

200

400

600

800

1000

1200

1400

0 500 1000 1500 2000

Rudra prayag

Jo

sh

imath

ii) Joshimath v Chamoli

Discharge Data (1971-82)

y = 1.3382x0.9039

R2 = 0.9057

0

100

200

300

400

500

600

700

0 200 400 600 800 1000

Chamoli

Jo

sh

imath


4-45

iii) Chamoli v Rudraprayag

Discharge Data(1977-82)

y = 0.5996x - 6.6157

R2 = 0.89670

100

200

300

400

500

600

700

800

900

0 200 400 600 800 1000 1200 1400 1600

Rudraprayag

Ch

am

oli


4-46

b) Double Mass Curve

Annual Discharge (Mm3)

Joshimath Chamoli Rudraprayag Year

1971-72 3,557 6,245

1972-73 3,890 7,124

1973-74 4,004 6,836

1974-75 4,403 5,330

1975-76 6,156 5,017

1976-77 5,105 6,181

1977-78 5,713 6,358 9,991

1978-79 5,996 6,553 9,751

1979-80 5,313 4,872 8,855

1980-81 5,658 5,159 10,431

1981-82 3,510 5,420 10,449

1982-83 3,266 9,393

1983-84 5,546 9,479

1984-85 5,544 8,126

1985-86 5,271 9,114

1986-87 6,178 10,054

1987-88 6,364 8,747

1988-89 6,290 10,270

1989-90 4,957 9,246

1990-91 5,759 11,384

1991-92 5,592 11,640

1992-93 5,451 11,275

1993-94 4,622 9,654

1994-95 4,804 12,220

1995-96 5,240 11,520

1996-97 5,762 12,095

1997-98 4,906 10,899

1998-99 16,181 17,623

1999-00 5,621 14,827

2000-01 3,784 12,832

2001-02 6,346 12,992

2002-03 5,932 11,673

2003-04 6,328 14,411

2004-05 5,767 12,056

2005-06 5,701 15,641

2006-07 3,663 12,438


4-47

Joshimath v Chamoli

Joshimath Chamoli Average Average Linear Residual Mass

0.000 0.000 0.000 0.000 0.000

3556.674 6245.004 6245.004 5113.799 -1557.125

7446.701 13368.636 13368.636 10947.072 -3500.372

11450.643 20204.940 20204.940 16545.064 -5094.422

15853.620 25535.400 25535.400 20909.977 -5056.357

22009.272 30552.252 30552.252 25018.088 -3008.816

27114.670 36733.308 36733.308 30079.522 -2964.852

32827.609 43091.316 43091.316 35285.856 -2458.246

38823.558 49644.672 49644.672 40652.152 -1828.594

44136.349 54516.984 54516.984 44641.905 -505.556

49794.792 59675.748 59675.748 48866.222 928.570

53304.302 65095.560 65095.560 53304.302 0.000

Joshimath v Rudraprayag

Joshimath Rudraprayag Average Average Linear Residual Mass

0 0 0 0 0

5,713 9,991 9,991 5,041 672

11,709 19,743 19,743 9,960 1,749

17,022 28,598 28,598 14,427 2,595

22,680 39,029 39,029 19,689 2,991

26,190 49,478 49,478 24,961 1,229

29,455 58,871 58,871 29,700 -244

35,002 68,351 68,351 34,482 520

40,546 76,477 76,477 38,581 1,965

45,817 85,591 85,591 43,179 2,638

51,995 95,644 95,644 48,251 3,744

58,359 104,392 104,392 52,664 5,695

64,649 114,661 114,661 57,845 6,804

69,606 123,908 123,908 62,509 7,096

75,364 135,291 135,291 68,252 7,112

80,956 146,932 146,932 74,125 6,831

86,407 158,207 158,207 79,813 6,595

91,029 167,860 167,860 84,683 6,346

95,833 180,080 180,080 90,847 4,986

101,073 191,600 191,600 96,659 4,414

106,835 203,695 203,695 102,761 4,074

111,741 214,594 214,594 108,259 3,482

127,923 232,218 232,218 117,150 10,773

133,544 247,044 247,044 124,630 8,914

137,328 259,876 259,876 131,103 6,224

143,673 272,868 272,868 137,658 6,016

149,605 284,541 284,541 143,546 6,059

155,933 298,952 298,952 150,817 5,116

161,700 311,008 311,008 156,899 4,802

167,401 326,649 326,649 164,789 2,612

171,064 339,088 339,088 171,064 0


4-48

Double Mass Curves

i) Joshimath v Chamoli

Double Mass Curve Analysis Joshimath v Chamoli

0

10,000

20,000

30,000

40,000

50,000

60,000

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

Accumulated annual discharge at Chamoli

Ac

cu

mu

late

d a

nn

ua

l d

isc

ha

rge

at

Jo

sh

ima

th

Residual Mass Curve

-6000

-5000

-4000

-3000

-2000

-1000

0

1000

2000

0 10,000 20,000 30,000 40,000 50,000 60,000

Accumulated annual disharge (Mm 3) of Chamoli

Resid

ual o

f accu

mu

late

d d

isch

arg

e (

Mm

3)


4-49

ii) Joshimath v Rudraprayag

Double Mass Curve Analysis Joshimath v Rudraprayag

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

0 50,000 100,000 150,000 200,000 250,000 300,000 350,000

Accumulated annual discharge at Rudraprayag

Accu

mu

late

d

an

nu

al

dis

ch

arg

e

at

Jo

sh

imath

Residual Mass Curve

-2000

0

2000

4000

6000

8000

10000

12000

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000

Accumulated annual disharge (Mm3) of Joshimath

Resid

ual

of

accu

mu

late

d d

isc

harg

e

(Mm

3)


4-50

Annex 4-5

Seasonal Regression Analysis for 1971-82

y = 8.8877x0.6591

R2 = 0.437

y = 1.9129x0.8865

R2 = 0.8261

y = 1.8229x0.8693

R2 = 0.81

0

100

200

300

400

500

600

700

800

900

1000

0 100 200 300 400 500 600 700

Joshimath

Ch

am

oli

June-Sep

Oct - Feb

Mar - May


4-51

Annex 4-6

Page 1/2

Year 1971-72 1972-73 1973-74 1974-75 1975-76 1976-77 1977-78 1978-79 1979-80 1980-81 1981-82 1982-83 1983-84 1984-85 1985-86 1986-87 1987-88 1988-89

Jun I 321 164 234 185 324 365 251 459 188 383 221 132 291 593 293 219 371 441

II 306 186 370 284 470 289 177 460 386 539 223 250 234 615 355 507 408 377

III 292 210 305 218 577 284 440 603 663 689 356 255 340 554 452 776 450 626

Jul I 278 330 320 284 498 413 682 706 585 710 363 397 438 575 436 622 652 670

II 216 233 320 411 716 592 748 540 701 795 439 431 402 463 536 709 590 784

III 311 239 333 486 623 711 678 635 641 827 515 434 639 568 519 865 786 879

Aug I 312 269 300 455 655 664 734 742 622 768 483 496 661 561 507 728 642 771

II 296 248 325 419 686 510 587 511 596 535 430 444 774 620 561 735 588 674

III 263 254 284 334 624 475 494 532 473 470 281 355 680 587 557 520 655 563

Sep I 220 369 266 285 518 492 466 418 423 372 223 194 543 482 434 465 538 435

II 169 369 263 234 403 372 300 298 230 189 215 157 433 362 333 318 420 288

III 152 212 262 210 270 226 214 289 141 152 160 97 296 180 261 265 353 294

Oct I 141 173 165 174 226 174 132 198 154 131 100 64 152 139 217 183 193 164

II 136 196 111 167 186 127 109 135 119 99 82 49 123 109 188 157 125 145

III 108 145 93 117 144 108 105 133 85 82 67 41 87 109 128 121 100 142

Nov I 109 129 85 94 115 94 97 103 76 70 52 36 68 80 99 106 90 124

II 76 109 90 85 94 86 77 78 65 60 43 33 61 67 80 93 79 106

III 62 91 77 74 86 80 68 93 56 49 37 27 53 57 69 78 69 88

Dec I 56 85 69 65 84 74 61 78 51 41 26 26 46 44 61 70 64 73

II 54 84 69 57 70 65 52 69 45 34 22 25 46 42 54 64 62 57

III 51 66 66 51 58 58 45 69 42 33 20 23 45 39 50 63 59 50

Jan I 53 58 57 48 51 51 44 55 40 33 19 21 44 38 50 60 56 42

II 55 55 50 46 43 49 42 52 39 30 17 20 44 34 47 59 54 37

III 48 50 54 48 40 49 41 50 38 33 17 20 42 41 46 58 50 38

Feb I 45 45 49 51 39 45 40 48 36 31 17 20 41 34 43 56 46 48

II 47 45 48 48 41 44 37 46 37 35 19 20 38 34 43 55 43 43

III 43 46 45 49 41 48 41 47 33 40 18 20 39 36 43 54 46 43

Mar I 43 44 51 52 44 50 44 47 35 36 21 22 46 42 42 54 55 47

II 44 50 56 54 44 53 48 52 34 39 20 25 44 40 44 54 69 49

III 53 56 65 69 50 61 48 63 37 44 27 28 56 49 44 58 71 52

Apr I 60 66 79 104 58 68 53 78 45 49 43 34 50 47 49 68 82 66

II 76 76 87 103 73 58 106 109 54 43 59 40 60 73 73 68 127 71

III 79 135 115 155 142 70 111 152 78 63 73 43 71 90 101 99 150 76

May I 93 263 194 175 151 77 190 177 188 144 84 59 145 117 163 103 195 85

II 162 191 170 278 211 107 332 211 217 157 83 140 292 148 297 99 262 181

III 203 168 143 264 258 138 391 152 269 206 96 144 428 305 185 137 407 272

Annual Total (Mm3) 4432 4835 4980 5496 7676 6374 7136 7466 6629 7060 4378 4081 6947 7029 6572 7703 7959 7857

Average Discharge 140.5 153.3 157.9 174.3 243.4 202.1 226.3 236.8 210.2 223.9 138.8 129.4 220.3 222.9 208.4 244.3 252.4 249.2

DISCHARGE DATA AT INTAKE - 10-DAILY AVERAGES

BOWALA NAND PRAYAG HEP


4-52

Annex 4-6

Page 2/2

Year 1989-90 1990-91 1991-92 1992-93 1993-94 1994-95 1995-96 1996-97 1997-98 1998-99 1999-00 2000-01 2001-02 2002-03 2003-04 2004-05 2005-06 2006-07

Jun I 353 452 435 230 334 353 373 385 196 530 223 437 435 363 470 204 178 334

II 306 386 507 405 461 365 611 596 234 492 416 520 541 443 480 246 298 187

III 352 623 542 428 398 523 254 776 426 1085 591 504 625 590 479 266 638 246

Jul I 364 587 652 351 470 544 459 496 483 1436 569 465 857 706 503 399 630 460

II 543 629 579 463 527 566 624 718 584 1565 550 571 887 714 510 350 687 549

III 669 508 661 524 442 675 640 737 705 1487 517 550 915 624 592 393 672 518

Aug I 421 523 517 536 496 515 721 752 485 1474 515 237 775 619 637 540 744 364

II 458 530 449 497 437 448 454 767 423 1344 483 164 707 426 642 629 571 311

III 551 440 419 461 423 465 460 525 326 1431 395 170 545 359 625 505 466 320

Sep I 369 436 396 428 371 418 467 496 348 1324 309 167 393 332 602 426 477 159

II 262 340 312 379 303 267 293 353 268 1244 307 97 293 277 529 425 381 145

III 215 289 238 254 219 183 215 264 178 1255 288 39 188 174 429 364 311 113

Oct I 144 211 204 224 164 153 170 171 116 1114 174 26 118 131 268 317 214 106

II 110 184 173 169 129 117 128 128 97 1050 104 48 86 133 227 304 172 87

III 98 140 129 151 113 94 82 94 82 1131 91 18 55 138 212 240 123 70

Nov I 79 110 118 129 78 61 66 74 71 1056 73 86 50 114 134 207 113 55

II 65 96 84 114 57 45 60 57 58 614 65 62 46 106 125 190 101 52

III 56 82 78 104 48 34 46 47 54 479 59 39 38 94 112 169 93 46

Dec I 50 61 73 91 45 31 36 43 51 467 63 30 34 79 102 145 80 42

II 47 51 61 82 36 28 32 38 48 457 82 28 32 73 89 124 66 40

III 41 47 54 72 32 48 28 33 45 209 75 26 31 68 79 114 53 39

Jan I 39 44 52 67 31 21 24 30 42 67 68 16 34 63 74 112 43 35

II 36 40 46 64 28 20 22 27 44 62 67 11 40 63 68 110 41 31

III 36 38 42 58 25 20 22 26 41 58 67 10 40 64 62 97 45 30

Feb I 34 37 36 57 24 20 20 24 42 52 71 12 39 64 65 96 41 28

II 35 37 37 62 23 20 19 23 41 53 66 11 39 65 66 104 41 30

III 34 36 34 57 25 20 22 22 38 51 68 12 42 72 68 109 42 30

Mar I 35 39 39 55 24 20 22 20 45 53 68 19 30 70 51 105 41 30

II 39 47 48 57 28 21 33 23 50 53 66 16 57 68 57 102 34 32

III 44 59 52 61 32 28 50 23 51 55 66 27 75 73 63 96 38 46

Apr I 49 61 81 64 45 25 49 27 76 65 102 24 85 96 65 113 46 58

II 84 69 56 94 47 31 101 32 89 90 111 40 107 132 69 106 57 62

III 135 123 128 186 45 65 135 63 178 200 136 82 128 173 79 103 54 70

May I 143 190 148 277 116 106 177 78 196 231 227 145 139 196 69 117 110 110

II 337 260 228 174 127 247 189 60 225 226 368 350 200 284 92 116 147 164

III 383 345 208 289 339 205 311 129 512 345 457 296 276 370 163 121 222 186

Annual Total (Mm3) 6214 7173 6968 6797 5770 6005 6542 7179 6146 20189 7007 4720 7921 7406 7883 7170 7105 4580

Average Discharge 197.0 227.5 220.9 215.5 183.0 190.4 207.5 227.6 194.9 640.2 222.2 149.7 251.2 234.9 250.0 227.4 225.3 145.2




4-53

Annex 4-7

Page 1/2

Ranking 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

2.7% 5.4% 8.1% 10.8% 13.5% 16.2% 18.9% 21.6% 24.3% 27.0% 29.7% 32.4% 35.1% 37.8% 40.5% 43.2% 45.9% 48.6% 51.4%

1998-99 1987-88 2001-02 2003-04 1988-89 1986-87 1975-76 1978-79 2002-03 2004-05 1996-97 1990-91 1977-78 2005-06 1980-81 1984-85 1999-00 1991-92 1983-84

Jun I 530 371 435 470 441 219 324 459 363 204 385 452 251 178 383 593 223 435 291

II 492 408 541 480 377 507 470 460 443 246 596 386 177 298 539 615 416 507 234

III 1085 450 625 479 626 776 577 603 590 266 776 623 440 638 689 554 591 542 340

Jul I 1436 652 857 503 670 622 498 706 706 399 496 587 682 630 710 575 569 652 438II 1565 590 887 510 784 709 716 540 714 350 718 629 748 687 795 463 550 579 402III 1487 786 915 592 879 865 623 635 624 393 737 508 678 672 827 568 517 661 639

Aug I 1474 642 775 637 771 728 655 742 619 540 752 523 734 744 768 561 515 517 661II 1344 588 707 642 674 735 686 511 426 629 767 530 587 571 535 620 483 449 774III 1431 655 545 625 563 520 624 532 359 505 525 440 494 466 470 587 395 419 680

Sep I 1324 538 393 602 435 465 518 418 332 426 496 436 466 477 372 482 309 396 543II 1244 420 293 529 288 318 403 298 277 425 353 340 300 381 189 362 307 312 433III 1255 353 188 429 294 265 270 289 174 364 264 289 214 311 152 180 288 238 296

Oct I 1114 193 118 268 164 183 226 198 131 317 171 211 132 214 131 139 174 204 152II 1050 125 86 227 145 157 186 135 133 304 128 184 109 172 99 109 104 173 123III 1131 100 55 212 142 121 144 133 138 240 94 140 105 123 82 109 91 129 87

Nov I 1056 90 50 134 124 106 115 103 114 207 74 110 97 113 70 80 73 118 68II 614 79 46 125 106 93 94 78 106 190 57 96 77 101 60 67 65 84 61III 479 69 38 112 88 78 86 93 94 169 47 82 68 93 49 57 59 78 53

Dec I 467 64 34 102 73 70 84 78 79 145 43 61 61 80 41 44 63 73 46II 457 62 32 89 57 64 70 69 73 124 38 51 52 66 34 42 82 61 46III 209 59 31 79 50 63 58 69 68 114 33 47 45 53 33 39 75 54 45

Jan I 67 56 34 74 42 60 51 55 63 112 30 44 44 43 33 38 68 52 44II 62 54 40 68 37 59 43 52 63 110 27 40 42 41 30 34 67 46 44III 58 50 40 62 38 58 40 50 64 97 26 38 41 45 33 41 67 42 42

Feb I 52 46 39 65 48 56 39 48 64 96 24 37 40 41 31 34 71 36 41II 53 43 39 66 43 55 41 46 65 104 23 37 37 41 35 34 66 37 38III 51 46 42 68 43 54 41 47 72 109 22 36 41 42 40 36 68 34 39

Mar I 53 55 30 51 47 54 44 47 70 105 20 39 44 41 36 42 68 39 46II 53 69 57 57 49 54 44 52 68 102 23 47 48 34 39 40 66 48 44III 55 71 75 63 52 58 50 63 73 96 23 59 48 38 44 49 66 52 56

Apr I 65 82 85 65 66 68 58 78 96 113 27 61 53 46 49 47 102 81 50II 90 127 107 69 71 68 73 109 132 106 32 69 106 57 43 73 111 56 60III 200 150 128 79 76 99 142 152 173 103 63 123 111 54 63 90 136 128 71

May I 231 195 139 69 85 103 151 177 196 117 78 190 190 110 144 117 227 148 145II 226 262 200 92 181 99 211 211 284 116 60 260 332 147 157 148 368 228 292III 345 407 276 163 272 137 258 152 370 121 129 345 391 222 206 305 457 208 428

Annual Total (Mm3) 20189 7959 7921 7883 7857 7703 7676 7466 7406 7179 7173 7170 7136 7105 7060 7029 7007 6968 6947

Average Discharge 640.2 252.4 251.2 250.0 249.2 244.3 243.4 236.8 234.9 227.6 227.5 227.4 226.3 225.3 223.9 222.9 222.2 220.9 220.3




4-54

Annex 4-7

Page 2/2

Ranking 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

54.1% 56.8% 59.5% 62.2% 64.9% 67.6% 70.3% 73.0% 75.7% 78.4% 81.1% 83.8% 86.5% 89.2% 91.9% 94.6% 97.3%

1992-93 1979-80 1985-86 1995-96 1976-77 1989-90 1997-98 1994-95 1993-94 1974-75 1973-74 1972-73 2000-01 2006-07 1971-72 1981-82 1982-83Jun I 230 188 293 373 365 353 196 353 334 185 234 164 437 334 321 221 132

II 405 386 355 611 289 306 234 365 461 284 370 186 520 187 306 223 250

III 428 663 452 254 284 352 426 523 398 218 305 210 504 246 292 356 255

Jul I 351 585 436 459 413 364 483 544 470 284 320 330 465 460 278 363 397II 463 701 536 624 592 543 584 566 527 411 320 233 571 549 216 439 431III 524 641 519 640 711 669 705 675 442 486 333 239 550 518 311 515 434

Aug I 536 622 507 721 664 421 485 515 496 455 300 269 237 364 312 483 496II 497 596 561 454 510 458 423 448 437 419 325 248 164 311 296 430 444III 461 473 557 460 475 551 326 465 423 334 284 254 170 320 263 281 355

Sep I 428 423 434 467 492 369 348 418 371 285 266 369 167 159 220 223 194II 379 230 333 293 372 262 268 267 303 234 263 369 97 145 169 215 157III 254 141 261 215 226 215 178 183 219 210 262 212 39 113 152 160 97

Oct I 224 154 217 170 174 144 116 153 164 174 165 173 26 106 141 100 64II 169 119 188 128 127 110 97 117 129 167 111 196 48 87 136 82 49III 151 85 128 82 108 98 82 94 113 117 93 145 18 70 108 67 41

Nov I 129 76 99 66 94 79 71 61 78 94 85 129 86 55 109 52 36II 114 65 80 60 86 65 58 45 57 85 90 109 62 52 76 43 33III 104 56 69 46 80 56 54 34 48 74 77 91 39 46 62 37 27

Dec I 91 51 61 36 74 50 51 31 45 65 69 85 30 42 56 26 26II 82 45 54 32 65 47 48 28 36 57 69 84 28 40 54 22 25III 72 42 50 28 58 41 45 48 32 51 66 66 26 39 51 20 23

Jan I 67 40 50 24 51 39 42 21 31 48 57 58 16 35 53 19 21II 64 39 47 22 49 36 44 20 28 46 50 55 11 31 55 17 20III 58 38 46 22 49 36 41 20 25 48 54 50 10 30 48 17 20

Feb I 57 36 43 20 45 34 42 20 24 51 49 45 12 28 45 17 20II 62 37 43 19 44 35 41 20 23 48 48 45 11 30 47 19 20III 57 33 43 22 48 34 38 20 25 49 45 46 12 30 43 18 20

Mar I 55 35 42 22 50 35 45 20 24 52 51 44 19 30 43 21 22II 57 34 44 33 53 39 50 21 28 54 56 50 16 32 44 20 25III 61 37 44 50 61 44 51 28 32 69 65 56 27 46 53 27 28

Apr I 64 45 49 49 68 49 76 25 45 104 79 66 24 58 60 43 34II 94 54 73 101 58 84 89 31 47 103 87 76 40 62 76 59 40III 186 78 101 135 70 135 178 65 45 155 115 135 82 70 79 73 43

May I 277 188 163 177 77 143 196 106 116 175 194 263 145 110 93 84 59II 174 217 297 189 107 337 225 247 127 278 170 191 350 164 162 83 140III 289 269 185 311 138 383 512 205 339 264 143 168 296 186 203 96 144

Annual Total (Mm3) 6797 6629 6572 6542 6374 6214 6146 6005 5770 5496 4980 4835 4720 4580 4432 4378 4081

Average Discharge 215.5 210.2 208.4 207.5 202.1 197.0 194.9 190.4 183.0 174.3 157.9 153.3 149.7 145.2 140.5 138.8 129.4




4-55

BOWALA NAND PRAYAG HEP Annex 4-8

Regional Flood data Page 1/3

Observed Peak Annual Discharges

River Ganga Baghirathi Yamuna Tons Ravi Beas Sarda Gandak Alaknanda Mandakini Alaknanda Satluj

Site Raiwala Tehri Tejewala Kishau Madhopur Pong Banbasa Bhainsalotan Rudraprayag Rudraprayag Joshimath Bakhra Dam

Catchment 22,396 7,511 11,120 4,885 6,075 12,540 14,975 ? 9,933 1,600 4,508 56,885

Year

1901 11,407

1902 9,163

1904 8,578

1905 9,078

1906 7,091

1907 7,545

1908 11,502

1908 7,406

1909 8,334 3,653

1910 11,886 11,959 5,635

1911 6,942 9,515 3,659

1912 8,334 9,323 6,705

1913 3,539 5,689 5,661

1914 9,248 9,707 7,079

1915 7,406 13,729 4,332

1916 4,725 11,959 3,766

1917 8,415 7,497 5,125

1918 4,665 2,874 1,982

1919 6,295 1,812 8,479 5,182

1920 8,173 3,037 8,752 4,248

1921 9,073 1,354 15,757 4,587

1922 7,406 3,037 7,149 4,446

1923 5,481 2,331 12,720 3,398

1924 19,134 14,158 6,711

1925 9,679 2,272 3,200 11,851 5,412

1926 3,697 3,373 3,135 7,932 3,455

1927 7,241 5,366 1,557 9,035 4,000

1928 3,697 2,387 1,812 10,809 2,398

1929 4,545 8,317 2,037 6,733 4,588

1930 5,997 10,268 4,389 6,796 7,323 6,938

1931 3,470 2,342 3,285 8,580 9,803 2,033

1932 6,155 7,553 4,440 10,675 9,611 5,040

1933 5,267 2,265 3,885 6,353 9,419 3,299

1934 9,024 2,549 2,185 14,781 11,642 4,332


4-56






Catchment 22,396 7,511 11,120 4,885 6,075 12,540 14,975 ? 9,933 1,600 4,508 56,885

1935 5,288 2,152 3,139 11,553 5,352 8,570 5,182

1936 3,320 3,358 5,465 9,713 6,541 11,225 4,007

1937 3,231 10,081 342 4,757 10,760 14,655 3,138

1938 3,535 2,487 2,651 4,389 3,766 10,809 5,805

1939 2,346 1,237 1,966 6,385 3,794 6,403 3,093

1940 2,429 2,631 3,262 5,140 3,285 7,758 1,723

1941 3,154 2,418 2,944 7,292 7,923 9,803 3,656

1942 6,649 6,468 391 11,709 8,048 6,569 6,598

1943 4,404 4,248 1,388 2,662 14,994 8,807 6,897 5,274

1944 4,229 2,869 595 3,242 12,884 6,739 6,238 2,294

1945 5,100 2,754 744 3,242 5,947 5,635 10,507 2,384

1946 4,741 4,657 782 2,931 12,516 5,069 9,515 3,819

1947 4,345 15,942 804 15,959 16,990 10,902 11,642 7,808

1948 4,890 3,846 1,128 2,855 6,385 6,626 9,904 4,531

1949 3,618 4,210 1,730 3,766 5,947 8,835 11,017 3,256

1950 6,181 3,660 1,680 6,272 6,824 7,192 13,277 4,984

1951 4,758 8,771 6,890 2,003 8,240 8,353 9,203

1952 3,919 3,721 1,950 2,860 6,654 5,012 9,416

1953 5,469 4,373 1,818 10,109 8,976 10,421 9,320

1954 6,384 7,151 1,090 4,113 10,534 8,693 19,535

1955 4,644 13,241 8,240 17,471 5,564 6,252 17,204

1956 6,382 12,752 5,780 6,570 8,240 7,476

1957 4,551 8,982 2,920 13,366 7,504 4,439 12,282

1958 4,056 4,234 657 3,625 4,870 10,421 9,129

1959 4,498 5,103 906 11,105 5,607 5,862 8,202

1960 3,883 2,274 355 5,601 9,231 10,740 8,848

1961 4,854 4,231 895 6,529 11,072 6,371 14,923

1962 5,759 6,193 2,355 5,287 6,626 9,168 9,416

1963 6,266 3,210 6,069 816 6,177 10,122 10,548

1964 3,756 4,000 1,992 697 5,947 4,524 10,251

1965 2,521 1,250 1,440 1,108 5,699 12,374 7,038

1966 4,740 3,300 2,901 1,305 8,572 7,249 9,359

1967 5,919 1,780 4,240 1,880 6,541 8,928 11,482 2,081

1968 3,319 2,480 3,375 1,800 3,483 7,311 13,450 1,058


4-57






Catchment 22,396 7,511 11,120 4,885 6,075 12,540 14,975 ? 9,933 1,600 4,508 56,885

1969 4,545 1,800 2,588 1,010 15,291 15,609 9,059 2,148

1970 5,169 4,130 2,463 1,225 4,850 9,750 7,566 2,200

1971 4,542 3,110 7,132 957 12,753 6,854 12,360 1,560 579 365

1972 4,160 1,460 5,730 996 2,812 12,632 10,126 2,887 572 545

1973 4,873 2,480 5,220 824 12,523 4,956 10,463 2,364 1,008 525

1974 4,785 3,400 8,084 726 12,969 4,603 11,463 1,782 456 575

1975 3,235 1,820 5,097 1,202 14,161 6,949 15,121 1,656 461 950

1976 6,783 2,700 8,162 1,160 7,844 9,603 13,946 1,887 452 880

1977 5,704 3,400 7,106 1,908 4,438 8,506 2,300 463 920

1978 12,985 7,200 20,085 6,600 5,650 15,525 2,811 635 1012

1979 3,116 2,100 740

1980 950

1981 565

1982 575

1983 990

1984 675

1985 750

1986 1100

1987 1425

1988 1232

1989 946

1990 1100

1991 960

1992 690

1993 630

1994 2077 592 1120

1995 2420 805 1350

1996 2028 443 1250

1997 2873 890 1150

1998 1800

1999 622

2000 1160

2001 1025

2002 875

2003 750


4-58

Annex 4-9

Page 1/3

Weight = 0.3

No. of Years N = 33

α =α =α =α = 0.44

Degree of Freedom ν = ν = ν = ν = 32 Confidence limits tc = 2.020

m Xext pProbability

percent T LogT Y XT SEx XC (+) XC (-)

1 3161.112 0.0169 1.691 59.143 1.7719 4.0714 3268.361 360.467 3996.504 2540.218

2 2502.547 0.0471 4.710 21.231 1.3270 3.0314 2788.223 274.155 3342.016 2234.430

3 2370.834 0.0773 7.729 12.938 1.1119 2.5202 2552.198 232.476 3021.800 2082.596

4 2195.217 0.1075 10.749 9.303 0.9686 2.1741 2392.407 204.753 2806.008 1978.806

5 2163.605 0.1377 13.768 7.263 0.8611 1.9097 2270.346 183.976 2641.977 1898.715

6 2037.161 0.1679 16.787 5.957 0.7750 1.6941 2170.809 167.389 2508.934 1832.684

7 2019.599 0.1981 19.807 5.049 0.7032 1.5108 2086.209 153.626 2396.534 1775.885

8 1966.914 0.2283 22.826 4.381 0.6416 1.3505 2012.203 141.914 2298.870 1725.536

9 1931.791 0.2585 25.845 3.869 0.5876 1.2073 1946.067 131.777 2212.256 1679.878

10 1931.791 0.2886 28.865 3.464 0.5396 1.0771 1885.974 122.901 2134.235 1637.713

11 1800.078 0.3188 31.884 3.136 0.4964 0.9572 1830.636 115.078 2063.093 1598.179

12 1777.247 0.3490 34.903 2.865 0.4571 0.8456 1779.108 108.159 1997.590 1560.626

13 1738.612 0.3792 37.923 2.637 0.4211 0.7407 1730.667 102.044 1936.797 1524.538

14 1685.926 0.4094 40.942 2.442 0.3878 0.6412 1684.750 96.662 1880.007 1489.493

15 1668.365 0.4396 43.961 2.275 0.3569 0.5462 1640.897 91.964 1826.665 1455.130

16 1668.365 0.4698 46.981 2.129 0.3281 0.4549 1598.732 87.921 1776.332 1421.131

17 1661.340 0.5000 50.000 2.000 0.3010 0.3665 1557.928 84.514 1728.646 1387.210

18 1615.679 0.5302 53.019 1.886 0.2756 0.2805 1518.202 81.735 1683.307 1353.097

19 1545.432 0.5604 56.039 1.784 0.2515 0.1962 1479.294 79.582 1640.050 1318.538

20 1536.652 0.5906 59.058 1.693 0.2287 0.1132 1440.961 78.057 1598.637 1283.286

21 1317.130 0.6208 62.077 1.611 0.2071 0.0309 1402.965 77.164 1558.837 1247.093

22 1317.130 0.6510 65.097 1.536 0.1864 -0.0513 1365.062 76.909 1520.418 1209.705

23 1299.568 0.6812 68.116 1.468 0.1668 -0.1337 1326.992 77.297 1483.133 1170.851

24 1211.760 0.7114 71.135 1.406 0.1479 -0.2172 1288.465 78.339 1446.709 1130.220

25 1185.417 0.7415 74.155 1.349 0.1299 -0.3024 1249.137 80.048 1410.834 1087.441

26 1106.389 0.7717 77.174 1.296 0.1125 -0.3902 1208.584 82.451 1375.134 1042.034

27 1092.340 0.8019 80.193 1.247 0.0959 -0.4819 1166.246 85.594 1339.147 993.346

28 1009.800 0.8321 83.213 1.202 0.0798 -0.5792 1121.345 89.562 1302.259 940.430

29 1009.800 0.8623 86.232 1.160 0.0643 -0.6845 1072.705 94.501 1263.598 881.812

30 992.238 0.8925 89.251 1.120 0.0494 -0.8022 1018.389 100.688 1221.778 814.999

31 957.114 0.9227 92.271 1.084 0.0349 -0.9401 954.731 108.680 1174.265 735.197

32 921.991 0.9529 95.290 1.049 0.0210 -1.1169 873.077 119.857 1115.188 630.966

33 641.003 0.9831 98.309 1.017 0.0074 -1.4061 739.582 139.746 1021.869 457.296

Xext(avg) = 1637.467 YN = 0.5388

Sext = 518.264 σσσσN = 1.1226

T YT XT T XT (m3/sec)

10 2430.590

59.143 4.071 3268.361 20 2841.252

21.231 3.031 2788.223 50 3384.117

500 6.214 ? 100 3794.779

500 4748.307

461.664 1000 5158.969

10000 6523.1584257.323 100000 7887.348

RT [Years] Discharge (m3/sec)

5 2081.19

10 2427.64

20 2759.96

30 2951.13

40 3085.91

50 3190.11

100 3512.45

500 4257.32

1000 4577.56

5000 5320.76

10000 5640.78

100000 6703.83

1600000 7983.83

Plotting Position No. by Gringerton

XT = Xext(avg) + KT * Sext

X500=

Computation for XT XT from Graph

Sext/σ/σ/σ/σN =

GUMBEL'S DISTRIBUTION

RESULTSCONFIDENCE LIMITS

Flood frequency analysis using GUMBEL'S EV : BNP

CONFIDENCE BAND

5.0

2

2)(

10.1)(

14.11,tan

−+−+= N

N

N

N

ext

X YYYYN

SSEdardErrorS

σσ

1, −= NfreedomofDegree ν


4-59

Annex 4-9

Page 2/3

Flood frequency_Gumbel: BNP

0

500

1000

1500

2000

2500

3000

3500

4000

4500

-2 -1 0 1 2 3 4 5Reduced Variate Y

XT

an

d X

c

XT Upper confidence limit Lower confidence limit Xext

XT

y = 592.46Ln(x) + 1066.4

R2 = 0.965

0

500

1000

1500

2000

2500

3000

3500

4000

1 10 100 1000 10000Return Periods [Years]

Rain

fall

XT (m3/sec)

Log. (XT (m3/sec))


4-60

Annex 4-9

Page 3/3

River Alaknanda

Site Bowala Weight = 1.3

Catchment 5,590

1 1971 641 2.81 0.141 -0.053

2 1972 957 2.98 0.040 -0.008 2 0.051 3.190 1547

3 1973 922 2.96 0.047 -0.010 5 0.853 3.310 2041

4 1974 1010 3.00 0.032 -0.006 10 1.244 3.368 2336

5 1975 1668 3.22 0.002 0.000 25 1.640 3.428 2678

6 1976 1545 3.19 0.000 0.000 50 1.885 3.465 2915

7 1977 1616 3.21 0.001 0.000 100 2.098 3.496 3137

8 1978 1777 3.25 0.005 0.000 200 2.378 3.539 3455

9 1979 1300 3.11 0.005 0.000 500 2.511 3.558 3618

10 1980 1668 3.22 0.002 0.000 1000 2.664 3.581 3814

11 1981 992 3.00 0.034 -0.006

12 1982 1010 3.00 0.032 -0.006

13 1983 1739 3.24 0.003 0.000 where ym & Sy are the mean and standard deviation of the logarithm of the sample

14 1984 1185 3.07 0.012 -0.001 KT is taken corresponding to coefficient of skewness

15 1985 1317 3.12 0.004 0.000

16 1986 1932 3.29 0.011 0.001

17 1987 2503 3.40 0.047 0.010

18 1988 2164 3.34 0.024 0.004

19 1989 1661 3.22 0.001 0.000

20 1990 1932 3.29 0.011 0.001

21 1991 1686 3.23 0.002 0.000

22 1992 1212 3.08 0.010 -0.001

23 1993 1106 3.04 0.019 -0.003

24 1994 1967 3.29 0.013 0.001

25 1995 2371 3.37 0.037 0.007

26 1996 2195 3.34 0.025 0.004

27 1997 2020 3.31 0.015 0.002

28 1998 3161 3.50 0.101 0.032

29 1999 1092 3.04 0.021 -0.003

30 2000 2037 3.31 0.016 0.002

31 2001 1800 3.26 0.005 0.000

32 2002 1537 3.19 0.000 0.000

33 2003 1317 3.12 0.004 0.000

Mean 3.18

Standard deviation 0.15

Coefficient of Skew -0.31

Log Pearson Type III Distribution

Log Pearson Type III Distribution

y = log QyT = ym + (KT* Sy) xT = 10y

T

(y-ym)2Year Peak Flow in cumecsS.No (y-ym)3

Return Period in

yearsKT

Log Pearson Type III (Bowala)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 100 200 300 400 500 600 700 800 900 1000 1100

Return Period

De

sig

n F

loo

d P

ea

k


4-61

Annex4-10 Page 1/15

1 Data

Length m

Area km2

Rainfall mm

Discharge m3/s or cumec

Level m

Slope m/km

Hour h or hour

Second s or sec

1.1

River Alaknanda

Arainfed 2850 km2

Asnowfed 2740 km2

Length of longest stream L 116 km

Length of the stream from CG Lc 71 km

Equivalent stream slope S 28 m/km

Design Loss Rate DLR 0.5 cm/h

1.2 Computation of Equivalent Slope

Sl No.

Reduced

distance

starting from

Site( km)

Reduced

levels of river

Bed (m)

Length of

each

segment

(km) Li

Height

above

datum (m)

Di

(Di-1+Di)

(m)

Li*(Di-1+Di)

(km*m)

1 2 3 4 5 6 7

1 0 762 0 0

2 30.583 1524 30.583 762 762 23304

3 57.289 2287 26.706 1525 2287 61077

4 82.811 3049 25.522 2287 3812 97290

5 101.287 3811 18.476 3049 5336 98588

6 116.169 4573 14.882 3811 6860 102091

7

8

9

10

11

12

13

14

Σ 116.169 Σ 382349

Slope = 28 m/km

Flood Analysis by Unit Hydrograph Method for HPP : BNP

Catchment characteristics

Ref. Zone-7 Flood

estimation report, CWC

( Ref. Toposheet )

The following units are consistently used unless specified otherwise

Catchment area


4-62

Annex4-10 Page 2/15

2 Synthetic 1-hr Unit Hydrogarph parameters

Catchment area A 2850 km2

Length of longest stream L 116 km

Length of the stream from CG Lc 71 km

Equivalent stream slope S 28 m/km

Design Loss Rate DLR 0.5 cm/h

tp = 6.053 2.498*(L*Lc/S)^0.156

qp = 0.761 1.048*tp^-0.178

W50 = 3.427 1.954*(L*Lc/S)^0.099

W75 = 1.964 0.972*(L*Lc/S)^0.124

WR50 = 1.670 0.189*(W 50 )^1.769

WR75 = 0.972 0.419*(W 75 )^1.246

TB = 16.921 7.845*tp^0.453

Tm = 6.553 tp+0.5

Qp = 2167.766 qp*A

TD = 6.659 1.1*tp

2.1

T0 0 0.0*Qp = 0

T50 4.8835 0.50*Qp = 1083.883

T75 5.5815 0.75*Qp = 1625.825

T100 6.5532 Qp = 2167.766

T75l 7.5458 0.75*Qp = 1625.825

T50l 8.3101 0.50*Qp = 1083.883

TB 16.9212 0.0*Qp = 0

Ref. Zone 7_Flood Estimation Report, CWC

Time 1 -hr SUH Ordinates

Key Points Ordinate

Unit Hydrograph by Sub Zone-7 report

0100200300400500600700800900

10001100120013001400150016001700180019002000210022002300

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Time (Hrs)

Dis

ch

arg

e (

cu

mec)

CWC Method

AdjustedOrdinates


4-63

50 Years

Bell-1 Bell-2 Bell-1 Bell-2

50 1.15 11.84 11.8 0.69 0.31 8.2 3.7

100 1.15 12.58 12.6 0.69 0.31 8.7 3.9

SPS 1.15 15.61 17.9 0.69 0.31 12.4 5.6

PMP 1.15 24.5 28.2 0.69 0.31 19.4 8.8

Time distribution and rainfall increments

1 0.17 0.5 1.418 1.4175 0.92 0.6 0.6 0.142

2 0.35 0.5 2.835 1.4175 0.92 1.3 0.6 0.142

3 0.49 0.5 4.016 1.1813 0.68 1.8 0.5 0.035

4 0.58 0.5 4.725 0.7088 0.21 2.1 0.3 0.000

5 0.64 0.5 5.198 0.4725 0.00 2.4 0.2 0.000

6 0.68 0.5 5.552 0.3544 0.00 2.5 0.2 0.000

7 0.74 0.5 6.024 0.4725 0.00 2.7 0.2 0.000

8 0.78 0.5 6.379 0.3544 0.00 2.9 0.2 0.000

9 0.84 0.5 6.851 0.4725 0.00 3.1 0.2 0.000

10 0.90 0.5 7.324 0.4725 0.00 3.3 0.2 0.000

11 0.94 0.5 7.678 0.3544 0.00 3.5 0.2 0.000

12 1.00 0.5 8.151 0.4725 0.00 3.7 0.2 0.000

Critical sequence of rainfall excess

0.0 0.0

1.0 20.0

2.0 60.0 0.00 0.00

3.0 130.0 0.00 0.00

4.0 400.0 0.00 0.00

5.0 1610.0 0.68 0.00 0.03 0.14

6.0 2165.6 0.92 0.00 0.14 0.14

7.0 1784.0 0.92 0.21 0.14 0.03

8.0 1026.8 0.21 0.92

9.0 380.0 0.00 0.92

10.0 160.0 0.00 0.68

11.0 70.0 0.00 0.00

12.0 40.0 0.00 0.00

13.0 30.0 0.00 0.00

14.0 20.0

15.0 10.0

16.0 5.0

17.0 2.0

18.0 0.0

Time

(hour)

1-hr UH

(cumec/cm)

Bell-1

Rainfall

Excess

(cm)

1-hr rainfall

increment

(cm)

Bell-2Rainfall

Excess

(cm)

Rainfall

Excess (cm)

Reversed

Rainfall

Excess

(cm)

Rainfall Excess

(cm)

Reversed

Bell-1

Distribution

co-efficient

Design

Loss rate

(cm/hr)

Bell-2

Storm

rainfall

(cm)

1-hr rainfall

increment

(cm)

Rainfall

Excess

(cm)

Hours

Ratio of 12-hr to 24 hr rainfall

P12/P24

Storm Distribution

(cm)

Rainfall Excess

Clock-hr

correction

factor

T [Years]Areal Rainfall

(cm)

Areal Rainfall

with Clock-hr

correction (cm)

Rainfall excess for

Storm

rainfall

(cm)

Annex4-10 Page 3/15


4-64

Annex4-10 Page 4/15

50 Years

Peak Flood = Q50 = 5335 Cumec

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0.209 0.918 0.918 0.681 0.142 0.142 0.035

0 0 0 0 323 323

1 20 4 0 4 323 328

2 60 13 18 0 31 323 354

3 130 27 55 18 0 101 323 424

4 400 84 119 55 14 0 271 323 595

5 1610 336 367 119 41 3 0 866 323 1189

6 2166 452 1477 367 89 8 3 0 2396 323 2720

7 1784 372 1987 1477 273 18 8 1 0 4137 323 4460

8 1027 214 1637 1987 1097 57 18 2 0 0 5012 323 5335

9 380 79 942 1637 1475 228 57 5 0 0 0 4423 323 4746

10 160 33 349 942 1215 307 228 14 0 0 0 0 3088 323 3411

11 70 15 147 349 700 253 307 56 0 0 0 0 0 1825 323 2148

12 40 8 64 147 259 145 253 75 0 0 0 0 0 0 951 323 1275

13 30 6 37 64 109 54 145 62 0 0 0 0 0 0 0 477 323 801

14 20 4 28 37 48 23 54 36 0 0 0 0 0 0 0 0 228 323 552

15 10 2 18 28 27 10 23 13 0 0 0 0 0 0 0 0 0 121 323 444

16 5 1 9 18 20 6 10 6 0 0 0 0 0 0 0 0 0 0 70 323 393

17 2 0 5 9 14 4 6 2 0 0 0 0 0 0 0 0 0 0 0 40 323 363

18 0 0 2 5 7 3 4 1 0 0 0 0 0 0 0 0 0 0 0 0 22 323 345

19 0 0 2 3 1 3 1 0 0 0 0 0 0 0 0 0 0 0 0 0 11 323 334

20 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 323 328

21 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 323 325

22 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 323 324

23 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 323 323

24 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

25 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

26 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

27 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

28 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

29 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

30 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

31 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

32 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

33 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

34 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

35 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

36 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

37 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

38 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 05335.427

Time

(hour)

BELL-1 (hours) BELL-2 (hours)

Base

Flow

(cumec)

Total Flood

(cumec)

Rainfall Excess (cm) Direct

Runoff

(cumec)

Flood estimation for return period RT =

Flood Hydrograph

1-hr UH

(cumec/cm)


4-65

Annex 4-10 Page 5/15

HYDROGRAPH [FLOOD] : 50 years 24 hours

0200400600800

1000120014001600180020002200240026002800300032003400360038004000420044004600480050005200540056005800

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Time [hour]

Dis

charg

e [C

um

ec]

Total Flood(cumec)


4-66

100 Years


50 1.15 11.84 11.8 0.69 0.31 8.2 3.7

100 1.15 16.5 16.5 0.69 0.31 11.4 5.1

SPS 1.15 15.61 17.9 0.69 0.31 12.4 5.6

PMP 1.15 24.5 28.2 0.69 0.31 19.4 8.8


1 0.17 0.5 2.0 2.0 1.48 0.9 0.9 0.39

2 0.35 0.5 4.0 2.0 1.48 1.8 0.9 0.39

3 0.49 0.5 5.6 1.6 1.15 2.5 0.7 0.25

4 0.58 0.5 6.6 1.0 0.49 3.0 0.4 0.00

5 0.64 0.5 7.2 0.7 0.16 3.3 0.3 0.00

6 0.68 0.5 7.7 0.5 0.00 3.5 0.2 0.00

7 0.74 0.5 8.4 0.7 0.16 3.8 0.3 0.00

8 0.78 0.5 8.9 0.5 0.00 4.0 0.2 0.00

9 0.84 0.5 9.5 0.7 0.16 4.3 0.3 0.00

10 0.90 0.5 10.2 0.7 0.16 4.6 0.3 0.00

11 0.94 0.5 10.7 0.5 0.00 4.8 0.2 0.00

12 1.00 0.5 11.4 0.7 0.16 5.1 0.3 0.00


0.0 0.0

1.0 20.0

2.0 60.0 0.00 0.00

3.0 130.0 0.16 0.00

4.0 400.0 0.16 0.16

5.0 1610.0 1.15 0.16 0.25 0.39

6.0 2165.6 1.48 0.16 0.39 0.39

7.0 1784.0 1.48 0.49 0.39 0.25

8.0 1026.8 0.49 1.48

9.0 380.0 0.16 1.48

10.0 160.0 0.16 1.15

11.0 70.0 0.16 0.16

12.0 40.0 0.00 0.16

13.0 30.0 0.00 0.00

14.0 20.0

15.0 10.0

16.0 5.0

17.0 2.0

18.0 0.0

Rainfall Excess

Clock-hr

correction

factor


(cm)

Areal Rainfall

with Clock-hr

correction (cm)

Rainfall excess for

Bell-2

Rainfall

Excess

(cm)

Bell-2

Ratio of 12-hr to 24 hr

rainfall P12/P24

Storm Distribution

(cm)

Storm

rainfall

(cm)

1-hr rainfall

increment

(cm)

HoursDistribution

co-efficient

Time

(hour)

1-hr UH

(cumec/cm)

Rainfall

Excess

(cm)

Rainfall

Excess (cm)

Reversed

Bell-1

Storm

rainfall

(cm)

Rainfall

Excess

(cm)

Design

Loss rate

(cm/hr)

Bell-1

Rainfall

Excess (cm)

Reversed

Rainfall

Excess

(cm)

1-hr rainfall

increment

(cm)

Annex4-10 Page 6/15


4-67

100 Years

Peak Flood = Q100 = 8709 Cumec

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0.158 0.158 0.158 0.488 1.475 1.475 1.146 0.158 0.158 0.394 0.394 0.245

0 0 0 0 323 323.340

1 20 3 0 3 323 326.509

2 60 10 3 0 13 323 336.018

3 130 21 10 3 0 33 323 356.619

4 400 63 21 10 10 0 103 323 426.593

5 1610 255 63 21 29 30 0 398 323 721.241

6 2166 343 255 63 63 89 30 0 843 323 1166.485

7 1784 283 343 255 195 192 89 23 0 1379 323 1702.710

8 1027 163 283 343 785 590 192 69 3 0 2428 323 2751.082

9 380 60 163 283 1056 2375 590 149 10 3 0 4689 323 5012.428

10 160 25 60 163 870 3195 2375 458 21 10 8 0 7185 323 7508.695

11 70 11 25 60 501 2632 3195 1845 63 21 24 8 0 8386 323 8708.922

12 40 6 11 25 185 1515 2632 2482 255 63 51 24 5 0 7256 323 7579.065

13 30 5 6 11 78 561 1515 2045 343 255 158 51 15 0 0 5043 323 5365.958

14 20 3 5 6 34 236 561 1177 283 343 635 158 32 0 0 0 3472 323 3795.420

15 10 2 3 5 20 103 236 436 163 283 854 635 98 0 0 0 0 2836 323 3158.873

16 5 1 2 3 15 59 103 183 60 163 703 854 395 0 0 0 0 0 2540 323 2863.512

17 2 0 1 2 10 44 59 80 25 60 405 703 531 0 0 0 0 0 0 1920 323 2243.598

18 0 0 0 1 5 30 44 46 11 25 150 405 437 0 0 0 0 0 0 0 1154 323 1477.202

19 0 0 0 2 15 30 34 6 11 63 150 252 0 0 0 0 0 0 0 0 563 323 886.721

20 0 0 0 1 7 15 23 5 6 28 63 93 0 0 0 0 0 0 0 0 0 241 323 564.265

21 0 0 0 0 3 7 11 3 5 16 28 39 0 0 0 0 0 0 0 0 0 0 112 323 435.630

22 0 0 0 0 0 3 6 2 3 12 16 17 0 0 0 0 0 0 0 0 0 0 0 58 323 381.526

23 0 0 0 0 0 0 2 1 2 8 12 10 0 0 0 0 0 0 0 0 0 0 0 0 34 323 357.523

24 0 0 0 0 0 0 0 0 1 4 8 7 0 0 0 0 0 0 0 0 0 0 0 0 20 323 343.628

25 0 0 0 0 0 0 0 0 0 2 4 5 0 0 0 0 0 0 0 0 0 0 0 0 11 323 334.472

26 0 0 0 0 0 0 0 0 0 1 2 2 0 0 0 0 0 0 0 0 0 0 0 0 5 323 328.550

27 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 2 323 325.354

28 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 323 323.830

29 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

30 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

31 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

32 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

33 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

34 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

35 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

36 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

37 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.000

38 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0008708.922

Base

Flow

(cumec)

Total Flood

(cumec)


Runoff

(cumec)


BELL-1 (hours) BELL-2 (hours)1-hr UH

(cumec/cm)

Time

(hour)

Annex4-10 Page 7/15


4-68

Annex4-10 Page 8/15

HYDROGRAPH [FLOOD] : 100 years 24 hours

0

400

800

1200

1600

2000

2400

2800

3200

3600

4000

4400

4800

5200

5600

6000

6400

6800

7200

7600

8000

8400

8800

9200

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Time [hour]

Dis

charg

e [C

um

ec]

Total Flood(cumec)


4-69

Annex4-10 Page 9/15

P1 = 2 inch A1 = 389 km2

P2 = 4 inch A2 = 346 km2

P3 = 6 inch A3 = 274 km2

P4 = 8 inch A4 = 253 km2

8 8 253 0.200 1.604

8-6 7 274 0.217 1.520

6-4 5 346 0.274 1.371

4-2 3 389 0.308 0.925

Total 1262 1.000 5.419

Pavg = 5.419 inch

P Acumulative GF

2 389 0.37

4 735 0.74

6 1009 1.11

8 1262 1.48

6.12 inch

15.6 cm

BNP intake lies in a region with the rainfall growth factor of 1.11 - 1.48. However, an eastward storm is indicative of low increment of rainfall.

Hence, a 2.5 % increment in growth factor corresponding to 6 inch rainfall i.e., (1.11+2.5%*1.13=1.13) is suitably adopted for BNP intake as it is in the proximity of 6 inch rainfall

and significantly, any further increment would not preserve the average rainfall.

The rainfall corresponding to the 1.33 growth factor is 6.14 inch = 15.61 cm and it is adopted as SPS for BNP intake.

Ref. Vishnugad Pipalkoti HEP DPR , 1-day SPS pattern in Vishnugad Pipalkoti HEP, Annexure-14-A, Fig.1

Storm pattern 1-Day SPS: BNP

The rainfall values from the isohyets in inches show that the storms are predominatly towards SW and EW directions

1-day SPS at BNP intake =

Weighted

P (inch)Isohytes

Fraction

of total

area

Area

(km2)

Average of

class

(inch)

Growth factor of rainfall

y = 0.1845x

R2 = 1

0.00.10.20.30.40.50.60.70.80.91.01.11.21.31.41.51.6

0 1 2 3 4 5 6 7 8 9

Pi (inch) [i=1..4]

Pi/P

avg

GF

Linear (GF)


4-70

Annex4-10 Page 10/15

SPS


50 1.15 11.84 11.8 0.69 0.31 8.2 3.7

100 1.15 12.58 12.6 0.69 0.31 8.7 3.9

SPS 1.15 15.61 17.9 0.69 0.31 12.4 5.6

PMP 1.15 24.5 28.2 0.69 0.31 19.4 8.8


1 0.17 0.5 2.1 2.15 1.65 1.0 1.0 0.47

2 0.35 0.5 4.3 2.15 1.65 1.9 1.0 0.47

3 0.49 0.5 6.1 1.79 1.29 2.8 0.8 0.31

4 0.58 0.5 7.2 1.0743 0.57 3.2 0.5 0.00

5 0.64 0.5 7.9 0.72 0.22 3.6 0.3 0.00

6 0.68 0.5 8.4 0.54 0.04 3.8 0.2 0.00

7 0.74 0.5 9.1 0.72 0.22 4.1 0.3 0.00

8 0.78 0.5 9.7 0.54 0.04 4.4 0.2 0.00

9 0.84 0.5 10.4 0.72 0.22 4.7 0.3 0.00

10 0.90 0.5 11.1 0.72 0.22 5.0 0.3 0.00

11 0.94 0.5 11.6 0.54 0.04 5.3 0.2 0.00

12 1.00 0.5 12.4 0.72 0.22 5.6 0.3 0.00


0.0 0.0

1.0 20.0

2.0 60.0 0.04 0.04

3.0 130.0 0.22 0.04

4.0 400.0 0.22 0.22

5.0 1610.0 1.29 0.22 0.31 0.47

6.0 2165.6 1.65 0.22 0.47 0.47

7.0 1784.0 1.65 0.57 0.47 0.31

8.0 1026.8 0.57 1.65

9.0 380.0 0.22 1.65

10.0 160.0 0.22 1.29

11.0 70.0 0.22 0.22

12.0 40.0 0.04 0.22

13.0 30.0 0.04 0.04

14.0 20.0

15.0 10.0

16.0 5.0

17.0 2.0

18.0 0.0

Rainfall

Excess

(cm)

Rainfall

Excess (cm)

Reversed

Bell-1

Storm

rainfall

(cm)

Rainfall

Excess

(cm)

Design

Loss rate

(cm/hr)

Bell-1

Rainfall Excess

(cm)

Reversed

Rainfall

Excess

(cm)

1-hr rainfall

increment

(cm)

HoursDistribution

co-efficient

Time

(hour)

1-hr UH

(cumec/cm)

Bell-2

Rainfall

Excess

(cm)

Bell-2


rainfall P12/P24

Storm Distribution

(cm)

Storm

rainfall

(cm)

1-hr rainfall

increment

(cm)

Clock-hr

correction

factor


(cm)

Areal Rainfall

with Clock-hr

correction (cm)

Rainfall excess for

Rainfall Excess


4-71


SPF

Peak Flood = QSPF = 9788.8 Cumec 9780 Cumec (say)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0.038 0.038 0.218 0.218 0.218 0.576 1.653 1.653 1.294 0.218 0.218 0.038 0.467 0.467 0.306

0 0 0 0 323 323

1 20 1 0 1 323 324

2 60 2 1 0 3 323 326

3 130 5 2 4 0 12 323 335

4 400 15 5 13 4 0 38 323 361

5 1610 62 15 28 13 4 0 122 323 446

6 2166 83 62 87 28 13 12 0 284 323 607

7 1784 68 83 350 87 28 35 33 0 684 323 1008

8 1027 39 68 471 350 87 75 99 33 0 1223 323 1546

9 380 15 39 388 471 350 231 215 99 26 0 1834 323 2157

10 160 6 15 223 388 471 928 661 215 78 4 0 2989 323 3313

11 70 3 6 83 223 388 1248 2661 661 168 13 4 0 5459 323 5782

12 40 2 3 35 83 223 1028 3579 2661 518 28 13 1 0 8173 323 8497

13 30 1 2 15 35 83 592 2949 3579 2083 87 28 2 9 0 9465 323 9789

14 20 1 1 9 15 35 219 1697 2949 2802 350 87 5 28 9 0 8207 323 8531

15 10 0 1 7 9 15 92 628 1697 2308 471 350 15 61 28 6 0 5689 323 6013

16 5 0 0 4 7 9 40 264 628 1329 388 471 62 187 61 18 0 0 3469 323 3792

17 2 0 0 2 4 7 23 116 264 492 223 388 83 752 187 40 0 0 0 2581 323 2905

18 0 0 0 1 2 4 17 66 116 207 83 223 68 1012 752 122 0 0 0 0 2674 323 2998

19 0 0 0 1 2 12 50 66 91 35 83 39 833 1012 493 0 0 0 0 0 2716 323 3039

20 0 0 0 0 1 6 33 50 52 15 35 15 480 833 663 0 0 0 0 0 0 2182 323 2505

21 0 0 0 0 0 3 17 33 39 9 15 6 178 480 546 0 0 0 0 0 0 0 1325 323 1648

22 0 0 0 0 0 1 8 17 26 7 9 3 75 178 314 0 0 0 0 0 0 0 0 636 323 960

23 0 0 0 0 0 0 3 8 13 4 7 2 33 75 116 0 0 0 0 0 0 0 0 0 261 323 584

24 0 0 0 0 0 0 0 3 6 2 4 1 19 33 49 0 0 0 0 0 0 0 0 0 118 323 441

25 0 0 0 0 0 0 0 0 3 1 2 1 14 19 21 0 0 0 0 0 0 0 0 0 61 323 384

26 0 0 0 0 0 0 0 0 0 0 1 0 9 14 12 0 0 0 0 0 0 0 0 0 38 323 361

27 0 0 0 0 0 0 0 0 0 0 0 0 5 9 9 0 0 0 0 0 0 0 0 0 24 323 347

28 0 0 0 0 0 0 0 0 0 0 0 0 2 5 6 0 0 0 0 0 0 0 0 0 13 323 337

29 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 0 0 0 0 0 0 0 0 0 6 323 330

30 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 0 0 0 0 0 0 0 0 0 2 323 326

31 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 323 324

32 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

33 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

34 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

35 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

36 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

37 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

38 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

9789

Base

Flow

(cumec)

Total Flood

(cumec)


Runoff

(cumec)


Flood Hydrograph

1-hr UH

(cumec/cm)

Time

(hour)BELL-1 (hours) BELL-2 (hours)


4-72


HYDROGRAPH [FLOOD] : SPF

0

400

800

1200

1600

2000

2400

2800

3200

3600

4000

4400

4800

5200

5600

6000

6400

6800

7200

7600

8000

8400

8800

9200

9600

10000

10400

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Time [hour]

Dis

charg

e [C

um

ec]

Total Flood

(cumec)9780 Cumec


4-73


PMP


50 1.15 11.84 11.8 0.69 0.31 8.2 3.7

100 1.15 12.6 12.6 0.69 0.31 8.7 3.9

SPS 1.15 15.61 17.9 0.69 0.31 12.4 5.6

PMP 1.15 24.5 28.2 0.69 0.31 19.4 8.8


1 0.17 0.5 3.4 3.4 2.87 1.5 1.5 1.03

2 0.35 0.5 6.7 3.4 2.87 3.1 1.5 1.03

3 0.49 0.5 9.6 2.8 2.31 4.3 1.3 0.77

4 0.58 0.5 11.2 1.7 1.19 5.1 0.8 0.26

5 0.64 0.5 12.4 1.1 0.62 5.6 0.5 0.01

6 0.68 0.5 13.2 0.8 0.34 6.0 0.4 0.00

7 0.74 0.5 14.3 1.1 0.62 6.5 0.5 0.01

8 0.78 0.5 15.2 0.8 0.34 6.9 0.4 0.00

9 0.84 0.5 16.3 1.1 0.62 7.4 0.5 0.01

10 0.90 0.5 17.4 1.1 0.62 7.9 0.5 0.01

11 0.94 0.5 18.3 0.8 0.34 8.3 0.4 0.00

12 1.00 0.5 19.4 1.1 0.62 8.8 0.5 0.01


0.0 0.0

1.0 20.0

2.0 60.0 0.34 0.34 0.00

3.0 130.0 0.62 0.34 0.01

4.0 400.0 0.62 0.62 0.01 0.01

5.0 1610.0 2.31 0.62 0.77 0.01

6.0 2165.6 2.87 0.62 1.03 0.01

7.0 1784.0 2.87 1.19 1.03 0.26

8.0 1026.8 1.19 2.87 0.26 1.03

9.0 380.0 0.62 2.87 0.01 1.03

10.0 160.0 0.62 2.31 0.01 0.77

11.0 70.0 0.62 0.62 0.01 0.01

12.0 40.0 0.34 0.62 0.00 0.01

13.0 30.0 0.34 0.34 0.00

14.0 20.0

15.0 10.0

16.0 5.0

17.0 2.0

18.0 0.0


rainfall P12/P24

Storm Distribution

(cm)

Rainfall Excess

Clock-hr

correction

factor


(cm)

Areal Rainfall

with Clock-hr

correction (cm)

Rainfall excess for

Time

(hour)

1-hr UH

(cumec/cm)

Bell-1

Rainfall

Excess

(cm)

Storm

rainfall

(cm)

Distribution

co-efficient

Design

Loss rate

(cm/hr)

Hours

Rainfall

Excess

(cm)

Rainfall Excess

(cm)

Reversed

Bell-2

Storm

rainfall

(cm)

1-hr rainfall

increment

(cm)

Rainfall

Excess

(cm)

Bell-1

1-hr rainfall

increment

(cm)

Bell-2Rainfall

Excess

(cm)

Rainfall

Excess (cm)

Reversed


4-74


PMF

Peak Flood = QPMF = 17367 Cumec

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0.343 0.343 0.624 0.624 0.624 1.187 2.873 2.873 2.311 0.624 0.624 0.343 0.009 0.009 0.009 0.263 1.027 1.027 0.772 0.009 0.009 0.000 0.000 0.000

0 0 0 0 323 323

1 20 7 0 7 323 330

2 60 21 7 0 27 323 351

3 130 45 21 12 0 78 323 401

4 400 137 45 37 12 0 232 323 555

5 1610 553 137 81 37 12 0 821 323 1144

6 2166 743 553 250 81 37 24 0 1688 323 2012

7 1784 612 743 1005 250 81 71 57 0 2821 323 3144

8 1027 353 612 1352 1005 250 154 172 57 0 3956 323 4280

9 380 130 353 1114 1352 1005 475 374 172 46 0 5021 323 5344

10 160 55 130 641 1114 1352 1910 1149 374 139 12 0 6877 323 7200

11 70 24 55 237 641 1114 2570 4626 1149 300 37 12 0 10766 323 11090

12 40 14 24 100 237 641 2117 6222 4626 924 81 37 7 0 15031 323 15354

13 30 10 14 44 100 237 1218 5126 6222 3721 250 81 21 0 0 17043 323 17367

14 20 7 10 25 44 100 451 2950 5126 5005 1005 250 45 1 0 0 15018 323 15341

15 10 3 7 19 25 44 190 1092 2950 4123 1352 1005 137 1 1 0 0 10949 323 11272

16 5 2 3 12 19 25 83 460 1092 2373 1114 1352 553 4 1 1 5 0 7098 323 7422

17 2 1 2 6 12 19 47 201 460 878 641 1114 743 14 4 1 16 21 0 4180 323 4504

18 0 0 1 3 6 12 36 115 201 370 237 641 612 19 14 4 34 62 21 0 2389 323 2712

19 0 0 1 3 6 24 86 115 162 100 237 353 16 19 14 105 133 62 15 0 1453 323 1776

20 0 0 0 1 3 12 57 86 92 44 100 130 9 16 19 424 411 133 46 0 0 1586 323 1909

21 0 0 0 0 1 6 29 57 69 25 44 55 3 9 16 570 1653 411 100 1 0 0 3050 323 3374

22 0 0 0 0 0 2 14 29 46 19 25 24 1 3 9 470 2224 1653 309 1 1 0 0 4831 323 5154

23 0 0 0 0 0 0 6 14 23 12 19 14 1 1 3 270 1832 2224 1243 4 1 0 0 0 5668 323 5991

24 0 0 0 0 0 0 0 6 12 6 12 10 0 1 1 100 1054 1832 1673 14 4 0 0 0 4726 323 5049

25 0 0 0 0 0 0 0 0 5 3 6 7 0 0 1 42 390 1054 1378 19 14 0 0 0 2920 323 3244

26 0 0 0 0 0 0 0 0 0 1 3 3 0 0 0 18 164 390 793 16 19 0 0 0 1410 323 1733

27 0 0 0 0 0 0 0 0 0 0 1 2 0 0 0 11 72 164 293 9 16 0 0 0 569 323 892

28 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 8 41 72 124 3 9 0 0 0 258 323 581

29 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 31 41 54 1 3 0 0 0 136 323 460

30 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3 21 31 31 1 1 0 0 0 87 323 410

31 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 10 21 23 0 1 0 0 0 56 323 380

32 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 5 10 15 0 0 0 0 0 32 323 355

33 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 5 8 0 0 0 0 0 15 323 339

34 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 4 0 0 0 0 0 6 323 330

35 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1.54 0.04 0.09 0 0 0 2 323 325

36 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.02 0.04 0 0 0 0 323 323

37 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.02 0 0 0 0 323 323

38 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0 0 0 0 0 0 0

17367

BELL-2 (hours)

Base

Flow

(cumec)

Total Flood

(cumec)


Runoff

(cumec)


Flood Hydrograph

1-hr UH

(cumec/cm)

Time

(hour)

BELL-1 (hours)


4-75


HYDROGRAPH [FLOOD] : PMF

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

16000

17000

18000

19000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Time [hour]

Dis

charg

e [C

um

ec]

Total Flood(cumec)

Documents

Hydrology Bowla Nand Prayag