Ganga Environmental Flow Calculator and its Applications

Nishadi Eriyagama

Kathmandu, NepalSeptember 2015

Outline• IWMI Environmental Flow Calculators

• Overview of the Ganga Environmental Flow Calculator

• Environmental Flow Estimation Method

• Example Applications from Sri Lanka

• The way forward

IWMI Environmental Flow Calculators

• Global Environmental Flow Calculator (GEFC)– Global coverage; gridded flow data

• Ganga Environmental Flow Calculator– Ganga Basin; location specific flow data

• Sri Lanka Environmental Flow calculator– Sri Lanka; location specific flow data

Ganga Environmental Flow Calculator

?

Desktop tool currently based on hydrology

Estimates flow for 6 Environmental Management Objectives (Environmental Management Classes A-F)

Uses environmental flow estimation method of Smakhtin & Anputhas (2006)

Provides 149 simulated flow time series from SWAT and WEAP models. User input also possible

Method based on constructing a Flow Duration Curve (FDC) from monthly “natural” flow time series

Environmental Management Classes

A Minor modifications Protected rivers

B Slightly modified Water supply/irrigation development allowed

C Habitat, biota disturbed, but basic functions intact

Dams, diversions, reduced water quality

D Large changes in habitat, biota and basic functions

Significant, clearly visible disturbances by regulation

E Habitat diversity declined. Only tolerant species exist

High population density and extensive development

F Total loss of natural habitat and biota

Unacceptable status

Estimation Method Developed by Smakhtin and Anputhas (2006)

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0100002000030000400005000060000

TimeMon

thly

Flo

w (

MCM

)

Natural Flow Time Series

0.01 0.1 1 5 10 20 30 40 50 60 70 80 90 95 99

99.9

99.99

110

1001000

10000100000

1000000

% Time Flow Exceeded

1972/01

1972/02

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1972/12

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01000020000300004000050000

Time

Natural Flow Duration Curve (FDC)

Environmental FDCs

Natural Time Series

Environmental Flow Time Series

A B C

A

B

Spatial Interpolation (Hughes and Smakhtin 1996)

Software at a glance

Example Applications

Assess current ecological condition against natural condition

Generate potential environmental flow scenarios

Mederipitiya

Udugama

Jasmin

Agliya KotmaleReservoir

Talawakelle

Peradeniya

Polgolla

Victoria Reservoir

Mallanda

Ullapane

Mahaweli

Gin Ganga

Example - Ullapane

KotmaleReservoir

Talawakelle

Peradeniya

Polgolla

Victoria Reservoir

Mallanda

Ullapane Ungauged

Gauged River Mahaweli

Gauged

Example – Ullapane

Talawakelle

Mallanda

PeradeniyaPolgolla

Ullapane

Establishing the natural flow Regime (Flow Duration Curve)

KotmaleReservoir

Victoria Reservoir

Hx

=

0 10 20 30 40 50 60 70 80 90 1001

10

100

1000

Peradeniya

Ullapane

Disc

harg

e (M

CM)/

mon

th

% of Time Flow Exceeded

Mallanda

Example – Ullapane

0 10 20 30 40 50 60 70 80 90 1001

10

100

1000

Dis

char

ge (M

CM

/mon

th)

% of Time Flow Exceeded

Comparison of Current Flow Regime with Environmental Flow Regimes

Natural Class A

Class B

Class C

Current

1 29 57 85 1131411691972252532813093373653934210

50

100

150

200

250

Months from January 1950

Disc

harg

e (m

3/s)

Flow

(M

CM

)

Current Natural Class A

Class B

Class C

Udugama

Jasmin

Agliya

Example - Mederipitiya

Ungauged

Gauged

Gauged

Gin Ganga

Mederipitiya

Example – Mederipitiya Establishing the natural flow Regime (Flow Duration Curve)

Mederipitiya

Udugama

Jasmin

Agliya

0 20 40 60 80 10010

100

1000

Udugama Jasmin

% of Time Flow Exceeded

Mederipitiya

Disc

harg

e (M

CM)/

mon

th

Example – Mederipitiya

Generation of Environmental Flow Scenarios

1 6 11 16 2110

20

30

40

50

60

70

80

Months from january 1980

Natural Class A Class B Class C

0 10 20 30 40 50 60 70 80 90 10010

100

1000

% of Time Flow Exceeded

Natural Class A

Class B Class C

Disc

harg

e (M

CM/m

onth

)

Disc

harg

e (M

CM/m

onth

)

Calibrating The Shifts

How?

Indicators based scoring system eg: Smakhtin et al. (2007) for Indian rivers (range, uniqueness, diversity of aquatic biota, degree of flow regulation and fragmentation etc.)

Link the phase of development of the river (as in Molden et al. 2001) to flow regime and have differential shifts within each phase “Development”, “Utilisation”, “Allocation”

Statistical approach: link human basin modifications and flow alterations eg: Homa et al. (2013) for rivers in the USA (population, road density, number of dams, dam storage etc.)

The Way Forward Provide planning level guidance for environmental flow estimation

“Calibrate” the FDC shifts to suit location-specific conditions

Incorporate an algorithm to estimate flows at ungauged sites

repository of all available observed/simulated flow time series in a region/country

THANK YOU!