Water Supply Analysis Lindsay Carr, Joey Kleiner, Kinsey Hoffman

7Q10

7Q10

average 7 day annual low flow with a 10 year return period

Consider 1 year of flow dataAverage over 7 consecutive days

Consider the 7 day averagesTake the lowest 7-day average for each year

Consider lowest flows for every yearFind annual low flow with a chance of occurring once

every 10 years

Importance in Water Supply Management

•Describes characteristics of a watershed

•Often used to regulate withdrawals• Amount of flow needed for water quality

standards• Amount of flow needed for habitat stability

Calculation Methods and Tools

DFLOW• EPA’s program for determining 7Q10

values

Matlab• Adapted a version from the University

of Georgia

R• Converted to R language from our

Matlab version

Log-

Pearson

Type III

Distribution

Log-Pearson Type III Distribution

Type of curve fitting for a frequency distribution common to hydrology

Log-Pearson Type III Distribution

DFLOW: Simplified version of the Log-Pearson III calculation within the program

Matlab: Calculates Log-Pearson III using multiple steps in the code

R: Uses a Log-Pearson III function within the code

Type of curve fitting for a frequency distribution common to hydrology

Add historic data

Specify flow averaging period

Specify the return period

Then calculate

DFLOW Interface

DFLOW Constraints• Requires user to download files from WOOOMM

• Find specific segment in WOOOMM• Export flow data as a text file

• User must alter the text file before importing to DFLOW• Header/footer of the exported results must be deleted

• Only a few segments can be calculated at a time

• Gives more than just 7Q10 value• Once calculated, users must separate the 7Q10 values

from the other calculations in the resulting table

Matlab Code

Specify query types within code rather than on WOOOMM

Automatically enters login information to access WOOOMM

Accesses data online rather than having to manually save it as a .txt file

Builds WOOOMM url to access data based on specified parameters

R Code

Specify query types within code

Build url to access data automatically

Can do multiple runs and segments at a time

Matlab and R Advantages• Automated data entry from WOOOMM

• Only a few specifications before running the code

• Results are automatically saved and returned to the WOOOMM database

• More detailed Log-Pearson Type III distribution is used

• Multiple segments and runs can be done all at the same time

Matlab

Current Work – Handling Zeroes

Large sections of 0.0 cfs values in the flow data

7 day average of 0.0 cfs

Annual low flow of 0.0 cfs log ( 0 ) = undefined

Current Work – Handling Zeroes

Conditional distribution – all values must remain non-zero

Unconditional distribution – accounts for zero flows

2. Frequency factor, K, is adjusted

1. Mean (x@) and standard deviation (S) is calculated with

all non-zero values

Current Work – Handling Zeroes

adjusted p

mean & standard deviation without

zeroes

𝑧=4 .91 [ (𝑃𝑎𝑑𝑗 )0 . 14− (1−𝑃𝑎𝑑𝑗 )

0 .14 ]

𝐾=( 2𝑔 )[(1+𝑔𝑧6 − 𝑔236 )3

−1]

𝑃𝑎𝑑𝑗=(𝑝 ∙𝑁𝑛 )−(𝑁−𝑛𝑁 )Vector without zeroes

z with adjusted p

Instream Flow Incremental Methodology (IFIM)

IFIM: Instream Flow Incremental Methodology • The goal of an IFIM study is to show

the relationship between stream flows and available aquatic habitat • This Flow:Habitat relationship is

necessary for assessing potential downstream impacts on habitat resulting from upstream flow alterations

• A main product of an IFIM study is the Weighted Usable Area (WUA) table- an index showing habitat suitability for a given species over a range of flows

Steps in the IFIM Process

1) Habitat identification 2) Transect selection 3) Species selection, habitat suitability criteria (HSC) compilation 4) Collection of field hydraulic and habitat data 5) Physical Habitat Simulation System (PHABSIM) model 6) PHABSIM output of “Weighted Usable Area” (WUA)

The Formation of Fish Habitat

• Fish habitat is dependent on:• Depth • Velocity • River bottom conditions

(substrate/cover)

• Depth and velocity conditions change with increasing flow

• Example: Riffles, runs, pools

The Mapping of Fish Habitat

• The first step in an IFIM study is the identification of aquatic habitats within the study area

• The stream is divided into “study reaches” at points where significant changes in channel morphology or flow occur • The primary types of

mesohabitats within these reaches need to be identified to facilitate transect site selection

The Mapping of Fish Habitat (cont.)

• Habitat mapping is achieved through the use of existing institutional knowledge, aerial photographs, GIS, GPS, and site-specific data obtained through “float trips”

Transect Locations

• Once the river reaches and habitat types are identified and mapped, transect locations for the collection of field hydraulic data are determined • Transects are located in areas

representative of the hydraulic/habitat conditions observed in that reach

Field Data Collection

• Physical Habitat Simulation (PHABSIM) software is used to simulate the relationship between streamflow and habitat for various species and life stages of fish • Data collected in the field at each transect location is used to calibrate

PHABSIM for the study reach of interest • Data is collected at sampling stations/cells equally spaced along each

transect • Data collected at each cell include: • Water surface elevation (WSE) • Water velocity • Substrate/cover

Field Data Collection (Cont.)

• WSE and velocity data are typically collected at each transect under 3 different “target flows” (low flow, medium flow, high flow) • The target flows observed at the transects are achieved by altering dam releases upstream • Example of target flows: 50, 150, and 300 cfs (measured by a USGS gage within the study reach)

• By entering the measurements taken at 3 flows, PHABSIM is able to interpolate WSE and velocity values for flows other than the 3 observed in the field

Field Data Collection (Cont.)

• Cover/substrate measurements are taken during the lowest target flow• Codes for cover/substrate are

assigned to each cell along a transect

Species Selection and HSC

• A set of fish species needs to be selected for Flow:Habitat analysis • The species selected must be present within the

study reach

• The species chosen are usually the ones most affected by changes in flow

• Each species has corresponding Habitat Suitability Criteria (HSC) that can be gathered from existing sources• HSC quantify habitat quality for each species/life

stage based on flow velocity, depth of the water column and substrate/cover

• HSC utilize a preference index ranging from 0 (least preferred) to 1 (most preferred)

PHABSIM Development

• A hydraulic model within PHABSIM is created for each study transect • The hydraulic model consists of a water surface model and a velocity model

• The water surface and velocity models are developed and calibrated using the 3 data sets obtained in the field (1 data set from each of the 3 target flows)

• The calibrated hydraulic model is able to simulate WSE and velocity values at each cell along the transect for any flow value• The hydraulic model at each transect is

combined with the HSC to produce a WUA table showing the Flow:Habitat relationship at that transect

PHABSIM Development (Cont.)

• HSC for water depths, water velocities and substrate/cover are used to rank the suitability of each model cell in a transect• This uses a multiplicative approach where suitability indexes (on a scale from 0.0 to 1.0) for a single

cell in a transect are multiplied together (depth*velocity*substrate) to produce a composite suitability score for that cell (0.0 to 1.0)

• The suitability score of a cell is used to weight the area of that cell to produce a “Weighted usable area” (WUA) value for that cell

• The weighted values for all cells in a transect are summed to produce a total WUA for that transect

WUA = suitability-weighted samples of area • WUA is an index to the microhabitat availability

WUA Development within PHABSIM

• By repeating this process for multiple species/lifestages over an entire range of flows, a WUA table can be produced for each transect displaying the flow:habitat relationship for each species/lifestage of interest

• The WUA tables from each transect in a reach can be averaged together using weighting factors to produce a single WUA table representative of the entire reach • WUA tables from each transect are weighted so that each transect's

contribution to the reach-WUA is indicative of the amount of each habitat type (% area) present in the reach • Area weighting factors are determined during the development of the habitat

maps

WUA Development within PHABSIM (Cont.) • Weighting transect-WUAs to produce a single reach-WUA table:

% of each habitat type present in a single reach

Weighting factors for each transect in the reach

WUA Example

WUA ExampleRedBSun

Juvenile Adult Spawning Adult Spawning Spawning Slow Fast Slow Fast10 8,650 4,062 18,545 1,585 112 19,431 8,020 288 17,310 1,17220 13,381 8,447 18,820 2,071 176 19,960 4,740 693 18,889 2,53640 22,200 16,204 18,799 3,537 293 19,972 2,488 1,137 21,407 5,26160 28,774 20,791 18,726 5,323 394 19,880 1,643 1,964 23,420 7,96980 32,940 22,872 18,496 7,642 482 19,876 1,532 2,631 25,292 10,168

100 36,522 24,433 17,592 10,083 574 19,626 1,479 2,807 26,489 12,558120 39,761 25,291 16,474 13,036 684 19,183 1,644 3,136 27,450 15,079160 44,456 26,838 13,635 19,659 893 16,465 1,062 3,354 28,132 20,133200 47,555 27,499 9,493 26,700 1,096 13,042 667 2,065 27,429 24,033250 49,959 28,079 7,368 33,427 1,247 11,139 615 1,564 26,722 27,576300 51,581 28,710 6,000 39,508 1,379 9,454 430 1,071 25,607 30,227350 52,257 28,869 4,792 44,866 1,456 7,854 486 737 24,197 30,935400 51,643 28,429 3,887 49,235 1,498 6,617 546 611 22,672 30,704450 50,249 27,458 3,261 52,640 1,477 5,411 645 517 20,851 29,608500 48,364 26,438 2,821 55,144 1,407 4,514 484 413 19,294 28,123550 46,047 25,640 2,554 56,623 1,322 3,889 334 333 17,737 26,710600 44,087 24,248 2,144 57,514 1,201 3,229 189 279 16,570 25,499650 42,233 23,011 1,925 58,020 1,099 2,898 155 197 15,305 23,741700 40,196 22,018 1,769 58,065 976 2,565 173 154 14,093 22,428750 38,186 20,711 1,503 57,884 831 2,121 196 125 12,972 20,835800 36,218 19,469 1,392 57,521 661 1,875 216 84 12,034 19,426900 33,366 17,012 1,114 56,349 469 1,557 186 51 10,274 16,857

1,000 29,379 14,898 962 54,663 329 1,339 122 31 8,706 14,5191,100 26,655 13,299 793 52,923 197 1,178 89 24 7,588 12,331

Smallmouth Bass N Hogsucker Shallow Guild Deep GuildWUA (ft²/1,000 ft stream)

Flow(cfs)

WUA ExampleRedBSun

Juvenile Adult Spawning Adult Spawning Spawning Slow Fast Slow Fast10 8,650 4,062 18,545 1,585 112 19,431 8,020 288 17,310 1,17220 13,381 8,447 18,820 2,071 176 19,960 4,740 693 18,889 2,53640 22,200 16,204 18,799 3,537 293 19,972 2,488 1,137 21,407 5,26160 28,774 20,791 18,726 5,323 394 19,880 1,643 1,964 23,420 7,96980 32,940 22,872 18,496 7,642 482 19,876 1,532 2,631 25,292 10,168

100 36,522 24,433 17,592 10,083 574 19,626 1,479 2,807 26,489 12,558120 39,761 25,291 16,474 13,036 684 19,183 1,644 3,136 27,450 15,079160 44,456 26,838 13,635 19,659 893 16,465 1,062 3,354 28,132 20,133200 47,555 27,499 9,493 26,700 1,096 13,042 667 2,065 27,429 24,033250 49,959 28,079 7,368 33,427 1,247 11,139 615 1,564 26,722 27,576300 51,581 28,710 6,000 39,508 1,379 9,454 430 1,071 25,607 30,227350 52,257 28,869 4,792 44,866 1,456 7,854 486 737 24,197 30,935400 51,643 28,429 3,887 49,235 1,498 6,617 546 611 22,672 30,704450 50,249 27,458 3,261 52,640 1,477 5,411 645 517 20,851 29,608500 48,364 26,438 2,821 55,144 1,407 4,514 484 413 19,294 28,123550 46,047 25,640 2,554 56,623 1,322 3,889 334 333 17,737 26,710600 44,087 24,248 2,144 57,514 1,201 3,229 189 279 16,570 25,499650 42,233 23,011 1,925 58,020 1,099 2,898 155 197 15,305 23,741700 40,196 22,018 1,769 58,065 976 2,565 173 154 14,093 22,428750 38,186 20,711 1,503 57,884 831 2,121 196 125 12,972 20,835800 36,218 19,469 1,392 57,521 661 1,875 216 84 12,034 19,426900 33,366 17,012 1,114 56,349 469 1,557 186 51 10,274 16,857

1,000 29,379 14,898 962 54,663 329 1,339 122 31 8,706 14,5191,100 26,655 13,299 793 52,923 197 1,178 89 24 7,588 12,331

Smallmouth Bass N Hogsucker Shallow Guild Deep GuildWUA (ft²/1,000 ft stream)

Flow(cfs)

Flow Statistics

Habitat Peaks (WUA)

Maximum Flow at Habitat Peaks

Median Flow at Habitat Peaks

Minimum Flow at Habitat Peaks

• Determine flow values at peak WUA values

August Low Flow (ALF)

• Median of the minimum flows on record in month of August• Used more for biological purposes • Is there enough water for

necessary biological functions in this late summer time period?• Calculated with R, stored in

WOOOMM• WOOOMM Comparison Link

Calculate median of the minimum flows

Percentile Flows

• Percent non-exceedance flows over a long period of recorded flow data• Ex: Flow on any given day is less than the long-term median flow (50th

percentile) only 50% of the time on record

• USGS calculates stats for their long-term gages • We can also calculate in WOOOMM

looking at August flow statistics

Flow Statistics Analysis Table

• Compare August Low Flow, percentile flows, and flows at habitat peaks for existing IFIM studies• See where flows at habitat peaks fall in relation to August Low Flow

and certain percentile flows

Flow-Habitat vs. Flow-Ecology

Old Science of Flow-Habitat Relationship• Observe changes in flow regime and

habitat structure• Flow regime: discharge, depth, velocity, flood

frequency/magnitude, drought frequency/magnitude• Habitat structure: biodiversity, bank stability,

streambed cover, riparian vegetation

• Create X-Y plot that shows how habitat varies with flow (IFIM & WUA)

Bovee et. al, 1998

FLOW

HAB

ITAT

Transition to Flow-Ecology

• Historically, find a single flow to maximize microhabitat for a life stage of high-profile fish species• Now widely accepted that a naturally variable

regime of flow, rather than just a single flow, is required to sustain freshwater ecosystems• Natural flow regime = range and variation of

flows over recent historical time • No single flow value will conserve an

ecosystem, or is optimal for all organisms and life cycles

Bovee et. al, 1998; Poff, 2010; Ahmadi-Nedushan et. al, 2006; Poff and Zimmerman, 2010

New Science of Flow-Ecology Relationship• Dubbed “flow alteration-ecological response

relationships”• Relate measures of ecological condition to

metrics of flow alteration• Ecological indicators: fish, macroinvertebrates,

algae and vegetation, riparian vegetation, wildlife, organic matter, nutrients, sediment

• Indicators of Hydrologic Alteration (IHA): 7Q10, August low flow, number of flood flow events, etc.

• Assess how flow regimes have been affected by human activities over time observe how ecosystem responds

Poff et. al, 2010;

Examples of Flow-Ecology

1. Flow Analysis table2. Comparison of flow metrics3. Percent changes in flow metrics4. When 7-day minimum flow occurs

Percent Change in 7Q10

August Low Flow

7Q10 Sept. Drought Warning

Month in which 7-day Min Occurs

Implications of Flow-Ecology

Strengths• Ecological condition can be

difficult to manage directly, but streamflow conditions can be managed through water-use strategies and policies • Use flow metrics as surrogate to

collecting habitat data• Expensive, time-consuming

Weaknesses• Rely too much on assumptions

between flow-ecology connections?• Are changes in flow regimes (and

thus changes in ecology) natural or anthropogenic?

Ahmadi-Nedushan et. al, 2006