Presented by IWMI's Nishadi Eriyagama at training event on the concept and application of maintaining Environmental Flows (EFlows) organized by IWMI in Kathmanu Nepal, on September 29, 2015.

1. Ganga Environmental Flow
Calculator and its Applications
Nishadi Eriyagama
Kathmandu, Nepal
September 2015

2. Outline
• IWMI Environmental Flow Calculators
• Overview of the Ganga Environmental Flow
Calculator
• Environmental Flow Estimation Method
• Example Applications from Sri Lanka
• The way forward

3. 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

4. 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

5. 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

6. Estimation Method
Developed by Smakhtin and Anputhas (2006)
0
10000
20000
30000
40000
50000
60000
1972/01 1973/07 1975/01 1976/07 1978/01 1979/07
MonthlyFlow(MCM)
Time
Natural Flow
Time Series
1
10
100
1000
10000
100000
1000000
0.01
0.1
1
5
10
20
30
40
50
60
70
80
90
95
99
99.9
99.99
% Time Flow Exceeded
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
1972/01 1973/07 1975/01 1976/07
Time
Natural Flow
Duration Curve
(FDC)
Environmental
FDCs
Natural Time Series
Environmental Flow
Time Series
ABC
A
B
Spatial
Interpolation
(Hughes and
Smakhtin 1996)

7. Software at a glance

8. Example Applications
Assess current ecological
condition against natural
condition
Generate potential
environmental flow
scenarios
Mederipitiya
Udugama
Jasmin
Agliya
Kotmale
Reservoir
Talawakelle
Peradeniya
Polgolla
Victoria
Reservoir
Mallanda
Ullapane
Mahaweli
Gin Ganga

9. Example - Ullapane
Kotmale
Reservoir
Talawakelle
Peradeniya
Polgolla
Victoria
Reservoir
Mallanda
Ullapane Ungauged
Gauged
River
Mahaweli
Gauged

10. Example – Ullapane
Talawakelle
Mallanda
Peradeniya
Polgolla
Ullapane
Establishing the natural flow Regime (Flow Duration Curve)
Kotmale
Reservoir
Victoria
Reservoir
Hx
𝐻 𝑥−𝐻 𝑚𝑎𝑙𝑙𝑎𝑛𝑑𝑎
𝐴 𝑥−𝐴 𝑚𝑎𝑙𝑙𝑎𝑛𝑑𝑎
=
𝐻 𝑝𝑒𝑟𝑎𝑑𝑒𝑛𝑖𝑦𝑎−𝐻 𝑚𝑎𝑙𝑙𝑎𝑛𝑑𝑎
𝐴 𝑝𝑒𝑟𝑎𝑑𝑒𝑛𝑖𝑦𝑎−𝐴 𝑚𝑎𝑙𝑙𝑎𝑛𝑑𝑎
1
10
100
1000
0 20 40 60 80 100
Peradeniya
Ullapane
Discharge(MCM)/month
% of Time Flow Exceeded
Mallanda

11. Example – Ullapane
1
10
100
1000
0 20 40 60 80 100
Discharge(MCM/month)
% of Time Flow Exceeded
Comparison of Current Flow Regime with Environmental Flow Regimes
Natural
Class A
Class B
Class C
Current
0
50
100
150
200
250
1 2 3 4 5 6 7 8 9 101112131415161718192021222324
Discharge(m3/s)
Months from January 1950
Flow
Current Natural
Class A
Class B
Class C

12. Udugama
Jasmin
Agliya
Example - Mederipitiya
Ungauged
Gauged
Gauged
Gin Ganga
Mederipitiya

13. Example – Mederipitiya
Establishing the natural flow Regime (Flow Duration Curve)
Mederipitiya
Udugama
Jasmin
Agliya
1
10
100
1000
0 20 40 60 80 100
Udugama
Jasmin
% of Time Flow Exceeded
Mederipitiya
Discharge(MCM)/month

14. Example – Mederipitiya
Generation of Environmental Flow Scenarios
10
20
30
40
50
60
70
80
1 6 11 16 21
Months from january 1980
Natural
Class A
Class B
Class C
10
100
1000
0 20 40 60 80 100
% of Time Flow Exceeded
Natural
Class A
Class B
Class C
Discharge(MCM/month)
Discharge(MCM/month)

15. Calibrating The Shifts
H
o
w
?
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.)

16. 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

17. THANK YOU!