Civil-V-hydrology and Irrigation Engineering [10cv55]-Assignment

Hydrology and Irrigation Engineering 10CV55

Dept of Civil Engineering, SJBIT Page 1

Assignment Questions

Unit 1: INTRODUCTION & PRECIPITATION

1. Define hydrology. With a neat sketch, explain the Horton's qualitative representation of

the hydrologic cycle.

2. Discuss briefly the importance of hydrology and its practical applications in civil

engineering.

3. Draw the Horton’s qualitative representation of hydrological cycle .Explain the cycle of

all components /phases?

4. Draw a neat sketch showing the catchment Hydrological cycle. Write down the 'water

budget' equation for any one of the zones.

5. Explain with neat sketch, Horton's Engineering representation of' Hydrologic cycle.

6. Hydrology is a highly inter - disciplinary science. Justify.

7. What are the seasons of India? Discuss the movement pattern of wind during monsoon

and retreating monsoon seasons in the country.

8. Describe the features - type, amount and distribution of rainfall, of the three seasons of

rainfall in Karnataka.

9. List out the various practical applications of hydrology?

10. Define precipitation. Explain different forms of precipitation?

11. What are the forms of precipitation? Explain any one of them?

12. Describe various types and forms of precipitation.

13. Describe the methods of recording of rainfall

14. What are the advantages and disadvantages of recording type of rainguage?

15. Describe the principle of working of a float type recording rainguage with a neat sketch.

Discuss its advantages and disadvantages.

16. Differentiate between recording and non - recording type of raingauges.

17. Critically compare recording rainguage (self) with non recording type rainguage.

18. Describe the three methods of determining the average depth of rainfall over an area.

Bring out the merits and demerits of each method.

19. An area is composed of a square of side 10 km and an equilateral triangles placed on the

left side. The annual precipitation recorded at four corners and the centre of the square

considered clock wise from the top left corner is 460mm, 650mm, 760mm, 800mm and



700mm respectively. The apex of the triangle has recorded 600mm of annual

precipitation. Find the mean precipitation over the area by Thiessen polygon method and

find the percentage difference with that of the arithmetic mean method.

20. Thiessen polygons constructed for a network of the raingauges in a river basin yielded.

Thiessen weights of 0.10, 0.16, 0.12, 0.11, 0.09, 0.08, 0.07, 0.11, 0.06 and 0.10. If the

rainfalls recorded at these gauges during a cyclonic storm are 132, 114, 162, 138, 207,

156, 135, 158, 108 and 150 mm respectively. Determine the average depth of rainfall by

Thiessen mean and arithmetic mean method.

21. A catchment is in the shape of an equilateral triangle placed over a square. Rain gauges

of the apex of the triangle and the next two successive corners of the square record 23, 18

and 16cm during a storm, determine the Theissen mean rainfall for the catchment.

22. A storm produced rainfall of 65, 74, and 100mm at three stations P, Q, and R

respectively. The normal annual rainfall at the stations X, P, Q and R are 660, 792, 786

and 1040 respectively. Estimate the missing storm rainfall at station X.

23. The normal annual precipitation of five rain gauge stations P, Q, R, S and T are 1200,

1020, 780, 1135 and 1350mm respectively. During a particular storm the precipitation

recorded by stations P, Q, R and S are 135, 95, 70 and 100mm respectively. The

instrument at 'T' is inoperative during that storm. Estimate the missing precipitation at

station T.

24. During a month, a rain guage went out of order while the other four gauges in the basin

reported rainfalls of 110, 90, 120 and 115mm. If the normal annual rainfall for these four

gauges are 115, 95, 125 and 120mm respectively and the normal rainfall for the broken

gauge is 98cm, estimate the monthly rainfall at the broken gauge.

25. Explain how the double mass curve method is used to test consistency of rainfall record.

26. Explain the method of checking rainfall data for consistency and show how records can

be adjusted for the current regime.

27. Estimate from depth –area curve , the average depth of precipitation that may be expected

over an area of 2400 Sq.km due to the storm of 27th

September 1978 which lasted for 24

hours. Assume the storm centre to be located at the centre of the area. The isohyetal as

map for the storm gave the areas enclosed between different isohyetes as follows.



Isohyet

(mm)

21 20 19 18 17 16 15 14 13 12

enclosed 54 134 203 254 295 328 353 371 388 391

Area

(km2)

3 5 0 5 5 0 5 0 0 5

28. The annual rainfall data being reported from a station A for 22 years are available, since

1969. In order to check the consistency of the data, six neighboring stations have been

chosen and the annual rainfall values of these stations have been averaged for all the

years on record since 1969. These values are given below:

Year

1969

1970

1971

1972

1973

1974

1975

1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

Yearly Precipitation

at station A in cm

177

144

178

162

194

168

196

144

160

196

141

158

145

132

95

148

142

140

130

137

130

163

Station average

yearly precipitation

in cm 143

132

146

147

161

155

152

117

128

193

156

164

155

143

115

135

163

135

143

130

146

161

` i) Find out if any inconsistency in precipitation record of station A is indicated. And if

yes, since when, a change in the precipitation regime is indicated?

ii) Adjust the recorded data at station A and determine its mean annual precipitation.

29. What are the recommendations of Indian standard institution on rain gauge network

establishment? Briefly explain optimum number of rain gauge stations in a catchment.

30. Explain the method of finding optimum number of rain gauges in a catchment.

31. A catchment has five rain gauge stations, which record 66, 74, 81, 69 and 90 cm of

rainfall in a year. Determine the percentage error in the arithmetic mean for the area. If

the error is to be 2% less than this, determine the additional number of stations required.

If you use a formula, derive it.

32. During a storm, one of the rain gauge stations 'X' failed to record the rainfall. Data in four

surrounding stations during the same storm are recorded as 7.5, 10, 12 and 9mm.

Coordinates of these four stations in km with station 'X' as the origin are (18, 4) , (-8, 16),



(-13, -21) and (-16, 23) respectively. Determine the missing rainfall record at station 'X’.

33. A catchment has 8 rain gauges of which one is a self recording type and 7 are the

standard type. For a 5% error in the estimation (E) of the mean rainfall, what should the

required no. of additional rain gauges, if annual precipitation at the 8 stations are?

Station A B C D E F G H

Rainfall (cm) 74 87 94 88 104 118 60 95

34. The average annual rainfalls in cm, at four existing raingauge stations in a basin are 105,

79, 70 and 66. If the average depth of rainfall over the basin is to be estimated within

10% error. Determine the additional number of gauges needed.

35. The annual rainfall at 7 rain gauge stations in a basin is 580, 940, 600, 450, 200, 880 and

680mm respectively. What is the percentage accuracy of the existing network in the

estimation of the average depth of rainfall over the basin? How many additional gauges

are required if it is desired to limit the error to only 10%.

36. A catchment has six rainguage stations. In a year, the annual rainfall recorded by the

gauges are as follows:

Station A B C D E F

Rainfall (cm) 82.6 102.9 180.3 110.3 98.8 136.7

For a 10% error in the estimation of the mean rainfall, calculate the optimum number of

stations in the catchment.

37. Define rainfall hyetograph. How to construct the double mass curve?

38. Explain mass curve analysis, with a neat sketch. Define intensity, duration and frequency

of rainfall.

39. Following are the rain gauge observations during a storm:

Time since start of storm, mins. 5 10 15 20 25 30 35 40 45 50

Accumulated rainfall , cms 0.1 0.2 0.8 1.5 1.8 2.0 2.5 2.7 2.9 3.1

Construct i) Mass curve of precipitation ii) Hyetograph.



40. The annual rainfall values at a P for a period of 20 years area as follows

Year 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985

Annual

rainfall

(cm)

120 84 68 92 102 92 95 88 76 84 101

Determine

i) The value of annual rainfall at P with a recurrence interval of 15 years.

ii) The probability of occurrence of an annual rainfall of magnitude 100cm at a station P

iii) 75% depenable annual rainfall at the station.

Unit 2: LOSSES FROM PRECIPITATION

1. Define evaporation. With a neat sketch, explain the measurement of evaporation using IS

class A pan.

2. Discuss briefly the various abstractions from precipitation.

3. Briefly explain "Evaporation Process".

4. Describe briefly a) Reference crop evapotranspiration b) Actual evapotranspiration

5. Distinguish between

a) Infiltration capacity and infiltration rate.

b) Actual and potential evapotranspiration

c) Field capacity and permanent wilting point

d) Depression storage and interception.

6. Define i) evaporation ii) potential evapo transpiration iii) Actual evapotranspiration iv)

Pan coefficient.

7. Describe the factors influencing evaporation rate from an open water surface. Define the

terms potential evapotranspiration and actual evapotranspiration, giving their relationship

with evaporation.

8. Explain how consumptive use can be estimated using the Blaney - Criddle method.

9. Describe the factor affecting evapotranspiration process.

10. State Dalton's law of evaporation and discuss the significance of each parameter in

Dalton's equation.



11. What is the actual evaporation, if 9 litres of water is removed from an evaporation pan of

diameter 1.22mm, to maintain the stipulated water level in the pan? A rainfall of 9mm

has been recorded simultaneously. Pan coefficient is 0.9 for the evaporation pan

considered.

12. Calculate the daily lake evaporation from the following data from a class A pan. Assume

pan coefficient-0.75.

13. Write a neat sketch showing the IS - Pan evaporatimeter. Describe how it is used to

measure the evaporation rates. What are its drawbacks?

14. Explain any three methods for determination of lake evaporation.

15. Describe the importance of pan coefficient in the determination of lake evaporation.

16. Define pan coefficient with a neat sketch. Explain the IS1 standard evaporation pan.

Explain i) Actual evapotranspiration ii) Potential evapotranspiration iii) Available

water.

17. What are the measures taken to reduce the rate of evaporation?

18. The water spread area in a lake nearby in the beginning of Jan in a year was 2.8 sq. km

and at the end of Dec it was measured as 2.55 sq km. Calculate the loss of water due to

evaporation assuming pan coefficient of 0.7.

19. Determine the E.T. and irrigation requirement for wheat, if the water application

efficiency is 65% and the (Cu) coefficient for the growing season is 0.8 from the

following data:

Month Mean monthly temp. °C Monthly % of sunshine hrs. Effective rainfall cm

Nov 18.0 7.20 2.6

Dec 15.0 7.15 2.8

Jan 13.5 7.30 3.5

Feb 14.5 7.10 2.0

20. Following are the data of average monthly percentage sunshine hours (p), mean monthly

Date 7/6/06 8/6/06 9/6/06 10/6/06 11/6/06

Rainfall (mm) 06 00 16 03 05

Water added (mm) +08 +12 -05 +10 +09



temperature (Tm) and vegetable's crop coefficient (k) for a place at 20°N latitude.

Month Jan Feb Mar April May June July Aug Sept Oct Nov Dec

P 7.73 7.26 8.2 8.52 9.14 9.2 9.25 8.95 8.30 8.19 7.58 7.88

Tm 12 15 16 20 22 22 20 20 15 10 11 8

K 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.8 0.7 0.65 0.55 0.5

If a farmer grows vegetables from July to December, what is total evapotranspiration

during that time period?

21. At site the value of evaporation in cm from Jan - Dec are 16.7, 14.3, 17.8, 25.0, 28.6,

21.4, 16.7, 16.7, 16.7. 21.4, 16.7, 16.7. Determine the evapotranspiration and irrigation

requirement for wheat if the water efficiency is 65% and the consumptive use coefficient for

the growing seasons following data.

22. Define infiltration. What are the factors that affect infiltration?

23. Explain the factors affecting infiltration capacity.

24. Explain the methods of estimating yield of a catchment.

25. Explain factors affecting Infiltration capacity.

26. What are infiltration indices? Distinguish between Φ - Index and W - Index.

27. Explain with a neat sketch, the method of determining infiltration.

28. Describe a double ring infiltrometer for measuring infiltration rate. What is the

significance of the outer ring?

29. Define infiltration. Explain how the constant fc, fo and k in the Horton’s equation can be

obtained from the Experimental data.

30. Total observed runoff volume during a 6 hr storm with a uniform intensity of 15mm/hr is

21.6xl06 cum. If the area of the basin is 300 sq.km, find the average infiltration rate for

Month Mean Monthly

Temperature (°C)

Monthly %

Sunshine hours

Effective

Rainfall (cm)

Nov 18 7.2 2.6

Dec 15 7.15 2.8

Jan 13.5 7.3 3,5

Feb 14.5 7.1 2.0



the basin.

31. A 6 hour storm produced rainfall intensities of 7, 18, 25, 12, 10 and 3mm / hr in

successive one - hour intervals over a basin of 800km2. The resulting runoff is observed

to be 2640 hectare - mt. Determine the ø - index of the basin. An infiltration test on a ring

with 35cm diameter yielded the following data.

Time from the starts

(mts) 0 2 5 10 20 30 60 90 150 120

Cumulative vol. of water

added (cm3).

0 178 658 1173 1924 2500 3345 3875 4595 5315

i) Determine the infiltration capacity rates for the time intervals.

ii) What is the average infiltration capacity for the first 10 minutes and for the first 30

minutes?

32. The rates of rainfall for the successive 30 min period of a 3 hr storm are 1.6, 3.6, 5.0, 2.8,

2.2, 1.0 cm/hr.

Corresponding surface runoff is estimated to be 3.6cm. Establish ø - index. Also determine

W - index.

33. Define infiltration. The rate of infiltration from the beginning of a storm are given below

Time (mm) 5 30 60 90 120 150 180 210 240

Rate of infiltration mm/hr 600 54 22 20 16 14 12 08 08

Fit an infiltration capacity curve of the exponential form.

34. A storm with 10.00 cm precipitation produced a direct runoff of 5.8 cm. Given the time

distribution of the storm as below, estimate the ø -index of the storm.

Time from start (hr) 1 2 3 4 5 6 7 8

Incremental rainfall in

each hour (cm) 0.4 0.9 1.5 2.3 1.8 1.6 1.0 0.5

35. The total observed run off volume during a 6 hour storm with a uniform intensity of 1.5

cm/hr is 21.6 x 106 m

3. If the area of the basin is 400 km

3, find the average infiltration

rate for the basin.

36. Explain briefly: i) infiltration capacity ii) ø - index iii) w - index.

37. Infiltration equation for a basin is given by f = 5 + 21e-4t

, where f is in mm/h and t is in

hours. Determine the values of initial infiltration capacity (f0), final steady infiltration rate



(fc) and decay coefficient (k). For a storm of intensity more than f0, determine

infiltration depth and average infiltration rate for first 15 and 60 minutes.

38. What are phi - index and w - index? Explain determination of effective rainfall of a

watershed by the phi - index method.

39. An infiltration test using a ring infiltrometer with 30cm diameter yielded the following

data :

Time from the start

(minutes)

0 2 5 10 20 30 60 90 150 210

Cumulative volume of

water added (cm3)

0 278 658 1173 1924 2500 3345 3875 4595 5315

i) Determine the infiltration capacity rates for the time intervals in the experiment.

ii) What is the ultimate infiltration capacity rate fc?

iii) What is the average infiltration capacity for the first 10 minutes and for the first 30

minutes of the experiment?

40. The infiltration rates measured during a test are listed below. Determine the parameters of

the Horton's curve, by the graphical procedure. (10 Marks)

Time (min) : 0.5 2.5 10 30 60 90 150

f(mm/h) : 8 7.5 6.8 5.6 3.6 2.1 2.0

41. Rainfall during the successive 15 minutes of a storm are 6, 20, 24, 28, 12 and 9mm.

Determine the Φ - index for the catchment, (Hint: consider Φ per 15 - minutes for

calculations) if the runoff is 39mm. (10 Marks)

42. A 6 hr storm producing rainfall intensities of 7, 18, 25, 12, 10 and 3mm/h in successive

one hour interval over a basin of 800 sq.km. The resulting runoff is observed to be 2640

ha -m. Determine the Φ - index for the basin.

43. The mass curve of a rainfall of duration 100 min is given below. If the catchment had an

initial loss of 0.6cm and Φ -index of 0.6cm/hr . Calculate the total surface runoff from the

catchment



Time from

start of

rainfall (min)

0 20 40 60 80 100

Cumulative

rainfall (cm)

0 0.5 1.2 2.6 3.3 3.5

44. In a 140-min storm the following rates of a rainfall were observed in successive 20-min

intervals 6.0, 6.0,18.0 ,13.0, 2.0, 2.0 and 12.0 mm/h . Assuming the Φ – index value as

3.0mm/h and a initial loss of 0.8mm, determine the total rainfall, net runoff and W- index

for the storm.

Unit 3:HYDROGPRAPH

1. Explain 'Unit hydrograph theory'. Derive the unit hydrograph from an isolated storm.

2. Define the term Runoff and list the various factors that affect the runoff of a given area.

3. Define Runoff. With a neat sketch, explain the runoff process.

4. What is unit hydrograph? Discuss its use and limitations.

5. Critically explain any five factors affecting runoff.

6. Compare any three methods used for determining runoff.

7. Distinguish between i) direct run off and base flow, ii) overland flow and interflow.

8. Briefly explain 'schematic representation of runoff components.

9. What are the components of hydrograph? Explain how base flow is separated from a

simple storage hydrograph.

10. With a neat sketch, explain the various components of a flood hydrograph. Also explain

any one method of base flow separation.

11. Write a note on water budget equation. List the factors affecting runoff.

12. Define runoff. Annual rainfall and runoff in mm, over a catchment area are given below :

Year 1980 81 82 83 84 85 86 87 88 89 90 91

Rainfall

(mm)

910 1110 605 1300 1470 990 1480 520 1195 900 660 750

Runoff

(mm)

305 515 245 620 750 403 654 165 472 390 275 230

Develop a rainfall - runoff relation by the method of least squares. Find the correlation



coefficient. If the rainfall for a particular year is 125cm, what will be the runoff for that

year?

13. The data in respect of a catchment are as follows :

Intensity of rainfall = 1 cm/hr; Duration of rainfall = 4 hours

Runoff coefficient = 0.5, 0.6, 0.7 and 0.8 for 1st hour, 2nd hour, 3rd hour and after 3rd hour

respectively.

Zone I II III IV

Area 20 ha 30 ha 50 ha 40 ha

Time of concentration 1 hr 2hr 3hr 4hr

Determine contribution to runoff from all the zones at the end of each hour starting 1st

hour ending 8th hour after commencement of rainfall.

14. Derive the unit hydrograph for a catchment of 200 km2

if the following discharges were

observed in the stream as a result of 6 – hour rainfall storm. The base can be assumed to

have increased linearly.

15. The ordinates of a 4h unit hydrograph of a basin area 630 Km2 measured at 2 hour

interval are given below. Obtain the ordinates of 6h unit hydrograph for the basin using S -

curve technique.

Time hrs 0 2 4 6 8 10 12 14 16 18 20 22 24

4h UH (cumec) 0 25 100 160 190 170 110 70 30 20 6 1.5 0

16. Derive the ordinates of a 3 – hour unit hydrograph, if the 6 - hour unit hydrograph for the

basin has the following ordinates (m3/s) at 3 – hour intervals: 0, 20, 80, 130, 150, 130, 90,

52, 27, 15, 5, 0. Work only up to the peak.

17. Given below are the monthly rainfall P and the corresponding runoff R values covering a

Time (hrs) 09 10 11 12 13 14 15 16

Discharge

(m3/s)

17 18 19 20 21 22 23 24 25 26



period of 18 months for a catchment. Develop a correlation equation between R and P.

Month 1 2 3 4 5 6 1 8 9

P 5 35 40 30 15 10 5 31 36

R 0.5 10 138 8.2 3.1 3.2 0.1 12 16

Month 10 11 12 13 14 15 16 17 18

P 30 10 8 2 22 30 25 8 6

R 8 2.3 1.6 0.0 6.5 9.4 7.6 1.5 0.5

18. Calculate Φ - index of a storm from the following data. Plot the rainfall histogram and

mark the Φ - index on the plot. Catchment area = 430 sq. km ; Volume of direct runoff

after separation of base flow = 10.75mm3 .

Runoff started at 3pm on 17/8/2007

Time of rainfall (hrs) 15 18 21 24 03

Depth of rainfall (mm) 12 15 09 22 02

19. A catchment is divided into five sub areas as given below :

Subarea (km'*) 1.5 3 2 1 2.5

Runoff coefficient (c) 0.7 0.6 0.4 0.55 0.9

Calculate the 25 year flood using the rational method. Assume a concentration time of 35

min and use the function

I = 75T0.22

, where I is in cm/hr and t is in min.

(t + 12)0.85

20. How do you determine the stage for zero discharge, if the stage and corresponding

discharge data of a stream

section are available?

21. Rainfall intensity of a Watershed of 5 sq.km area is given by

I= 100Tr0.2

….mm/hr

(t + 16)0.8

where Tr = return period in years and t = time of concentration in minutes. The watershed

has a slope of 0.005 with maximum travel length of 2000m, the land use pattern has 20%

agricultural land (c = 0.3), 10% forest land (c = 0.16) and rest is impervious.

Estimate 50 year peak flood for the area, c = coefficient of runoff.



Unit -4: ESTIMATION OF FLOOD & FLOOD ROUTING

1. What do you mean by the term flood? Mention any two factors affecting flood?

2. Mention any two empirical formulae for estimating flood?

3. What do you mean by flood control? Explain any two methods of flood control.

4. Distinguish between

a) Hydraulic and hydrological method of flood routing

b) Hydrologic storage routing and hydrologic channel routing

c) Prism storage and wedge storage.

5. What are the basic equations used for flood routing

a) Hydrologic method and hydraulic method.

6. Describe a numerical method of hydrologic reservoir routing.

Unit -5: INTRODUCTION TO IRRIGATION

1. Define the term irrigation. What are the reasons for adopting it?

2. Define irrigation. What is the necessity of irrigation?

3. Define Irrigation. What are the types of flow irrigation? Explain any two flow irrigation

systems.

4. What are the benefits and ill effects of irrigation?

5. List the benefits of irrigation.

6. What are the benefits that can be accrued from irrigation projects? Explain in brief.

7. List the benefits and ill effects of irrigation.

8. Explain Flow irrigation with the help of neat sketches.

9. List the methods of irrigation and explain any three methods.

10. What are the primary objectives of an irrigation method? List the various methods of

irrigation adopted for distribution of water in the field.

11. List out the various methods of application of irrigation water. (including subgroups)

12. What are the methods of applying water to crops? Explain any two surface irrigation

methods.

13. What is Bandhara irrigation? What are its advantages and disadvantages? Explain Phad



system of irrigation.

14. With neat sketches, explain Bandhara irrigation. List its advantages and disadvantages.

15. Discuss Phad system of irrigation as applied to Bhandhara irrigation.

16. List the advantages of sprinkler irrigation, with its limitations.

17. What are the limitations of sprinkler irrigation system?

18. Explain drip irrigation. List its advantages and disadvantages.

19. Write short notes on supplemental irrigation.

20. Write a short note on infiltration galleries.

Unit – 6: SOIL-WATER-CROP RELATIONSHIP

1. Give brief classification of Indian soils.

2. What are the functions of irrigation soils? Explain briefly.

3. What are the physical properties of soil?

4. Explain frequency of irrigation and irrigation efficiency.

5. Define crop rotation. What are its advantages? List some crop rotations.

6. How do you estimate the frequency of irrigation on the basis of soil moisture basis?

7. After how many days will you supply water to soil (clay loam) in order to ensure efficient

irrigation of the given crop if:

i) Field capacity of soil is 27% ii) Permanent wilting point is 14%.

iii) Density of soil is 1.5 g/cc iv) Effective depth of root zone is 75cm

v) Daily consumptive use of water for the given crop is 11mm.

8. After how many days will you supply water to soil in order to ensure sufficient irrigation

of the given crop, if the field capacity of the soil = 30%, permanent wilting point = 14%,

density of soil = 0.0125 N/cm3, effective depth of root zone = 70 cm and daily

consumptive use of water for the given crop = 10.5 mm.

9. After how many days will you supply water to soil in order to ensure sufficient irrigation

of given crop, if

Field capacity of soil = 28%

Optimum moisture content, when water is be supplied = 16%

Dry density of soil =13 kN/m3

Effective root zone depth = 0.7 m



Daily consumptive use of water for given crop =12 mm

10. Calculate the depth of available soil moisture in the root zone of the clay loamy soil using

the following data. Also find after how many days will you supply water to the soil in

order to ensure efficient irrigation of the given crop if

Field capacity = 27%

Permanent wilting point = 13%

Dry density of soil = 1.5 gm/cm

Root zone depth = 1.25 m

Daily consumptive use of water for the given crop = 20 mm.

11. After how many days will you supply water to soil (clay loam) in order to ensure efficient

irrigation of the given crop if,

Field capacity of soil = 27%

Permanent wilting point = 14%

Density of soil =13 kN/m3

Effective depth of root zone = 0.75 m

Daily consumptive use of water for the given crop =1.1 cms

12. When will a soil be fertile? How can soil fertility be maintained?

13. Write a note on crop rotation?

Unit –7 :WATER REQUIREMENT OF CROPS

1. What do you mean by Duty and Delta? How are they expressed?

2. Define duty, delta and base period. Obtain the relationship between them.

3. Define 'flow duty' and 'quantity duty'. Obtain the relationship between Duty, Delta and

Base period.

4. Explain i) Gross command area ii) Culturable command area iii) Consumptive use

5. Define duty, delta and base period and establish the relationship between them.

6. What are the factors affecting duty?

7. Define various irrigation efficiencies used in irrigation system.

8. A water course commands an irrigation area of 800 ha. The intensity of irrigation for rice

in this area is 50%. The transplantation of rice crop takes 15 days and the total depth of

water required by the crop is 60 cm. Determine i) Duty on the field during

transplantation ii) Duty at the head of distributory assuming losses of water to be 20% in



the water courses. iii) Calculate the discharge required in the water course.

9. Culturable command area under a canal system is 50000 hectares. Base period, intensity

of irrigation and duty of various crops are given in the table below. Determine the

discharge for which the canal is to be designed.

Crop Base period

(days)

Intensity of

Irrigation (%)

Duty

(hectares / cumec)

Kharif 110 30 900

Rabi 120 45 2000

Sugarcane 360 20 2500

10. The base period, duty at the field of difference crops, and area under each crop in the

command area are given below. Find the required reservoir capacity to cater to the needs

of the crops.

Crops Base period

(days)

Duty @ field

(Ha/cumec)

Area under the

crop (Ha)

Wheat 120 1800 4800

Sugar cane 360 800 5600

Cotton 200 1400 2400

Rice 120 900 3200

11. A main canal taking off from a storage reservoir has to irrigate a land with the following

crops, the details of which are given below.

Crop Crop period

(days)

Area to be irrigated

(Hectares)

Duty

(Hect/cumec)

Sugar cane (Perinnial ) 365 1250 850

Paddy (Kharif) 120 1500 850

Wheat (Rabi) 120 2500 1700

Assuming 25% losses in the canal system and giving an allowance of 20% for peak

demand, calculate the capacity of the main canal. What is the total volume of water

required for each crop?

12. Culturable command area of a reservoir is 50000 hectares. Find out the reservoir



capacity, if the canal losses are 5% and reservoir losses 8%. Base period, intensity of

irrigation and duty of various crops are given in the following table:

Crop Base period

(days)

Duty

(hect/cumecs)

Intensity of irrigation

(%)

Wheat 120 2000 20

Rice 140 900 15

Cotton 180 1600 10

Sugarcane 360 2500 20

13. What shall be the reservoir capacity for the season, if it is serving 24000 ha of paddy,

6000 ha of ground nut, 6000 ha of maize and 12000 ha of cotton? The following depth

(cm) of water is required during different months?

Month Paddy Ground

nut Maize Cotton

September (1-30) 7.9 — — —

October (1-31) 29.9 — 3.4 4.0

November (1-30) 20.7 6.3 15.1 8.0

December (1-31) — 16.2 23.8 20.6

Assume 25% canal losses and 20% reservoir evaporation losses.

Unit – 8: CANALS

1. With a neat sketch, explain any one type in each of cross drainage work

2. Carrying canal water over the drainage ii) Carrying drainage over the canal.

3. What is a Canal? Explain the general considerations for alignment of Canals.

4. Explain various considerations for alignment of a canal.

5. With a neat sketch, explain the cross drainage works constructed for bypassing canal over

drainage.

6. Design an irrigation channel in alluvial soil according to Laceys silt theory for the



following data: Full supply discharge=10 cumec, Lacey’s silt factor=0.9, Side slope of

channel=½(H):1(V)

7. Design an irrigation channel to carry a discharge of 45 cumecs. Assume N = 0.0225 and

m = 1. The channel has a bed slope of 0.16 meter per kilometer. Use Kennedy's theory.

Assume a trial depth for D as 1.8m.

8. An irrigation engineer has designed an irrigation canal using Kennedy's theory, for the

following details. He had concluded that full supply depth of 1.8 m is sufficient for the

canal. Check whether his design can be adopted.

Discharge = 45 cumecs

Manning's Rugosity coefficient = 0.0225

Bed slope of channel =0.16 m/km

Critical velocity ratio =1

9. Give the classification of canals. Explain salient features of each of them.

10. Write the steps involved in hydraulic design of an aqueduct.

11. Design an irrigation canal for the following data using Lacey's silt theory. Full supply

discharge = 35 cumec, silt factor = f = 1 side slope = 1H : 2V.

12. What are the factors to be considered in alignment of an irrigation canal? What are the

main functions of head regulator and cross regulator?

13. A channel section has to be designed for the following data:

Discharge Q = 30 cumecs, Silt factor f - 1.00, Side slope : 0.5 H : 1 V

Find also the longitudinal slope.

14. List the functions of head regulator and cross regulator work.

15. Design an irrigation channel in alluvial soil according to Lacey's silt theory for the

following data: Fully supply discharge =15 m/sec; Lacey's silt factor = 1.0; Side slope

of channel =2 H: 1V

16. "Lacey's conception of design of canal on an alluvial soil is superior to Kennedy’s

concept". Justify the statement.

17. Explain the design principle of trapezoidal notch type of fall.

18. Design an irrigation channel to carry 50 cumecs of discharge. The channel is to be laid at

a slope of 1 in 4000. Take CVR = 1.1 and Chezy's C - 49.726 in the equation V = C RS.

Assume trial depth = 2.7 m. Whether the trial depth is suited for the discharge?

Documents

Civil-V-hydrology and Irrigation Engineering [10cv55]-Assignment