1

Environmental Flows in : Assessment of Environmental Flows in Myitnge River Basin

Presenter Su Su Hlaing Technological University Myanmar 2

Environmental flow

. Enough water that is left in the river, or release into it to manage downstream environmental, social and economic benefits. (Dyson et al., 2008)

. Quantity, quality and timing of water flows required to sustain freshwater , ecosystem and human livelihoods and well‐being that depend on these ecosystem. (Richter et al.,2003) 3

STUDY AREA

Catchment 28206 km2 area Annual mean 483 m3/sec discharge at dam site Full supply EL 185 m level Minimum EL 150 m operation level Gross storage 2611 MCM capacity Dead storage 992.8 MCM capacity Installed 790 MW capacity (197.5 x 4 units) Maximum plant 210 m3/sec discharge Rated head 91m Before Dam 1981 2009 Data Length Average Annual 3550 GWh Energy After Dam 2011 2018 4 Hydrograph of Myitnge River Before Yewa Dam (1982) Shape physical character of river channel, including pools, riffle Adequate habitat for Restore normal water quality conditions after prolonged low flows aquatic organisms Replenish the ground water

Soil moisture for plants

Recruitment of certain floodplain plant species Flood Season

2500 Deposit nutrients rich on floodplain High Flow Pulse and gravel and 2000 cobbles in spawning areas

1500 /sec) 3 Enable fish to spawn (m

in floodplain, 1000 provide nursery area for juvenile Flow 500

Recharge floodplain 0 water table 01/Nov 01/Dec 01/Jan 01/Feb 01/Mar 01/Apr 01/May 01/Jun 01/Jul 01/Aug 01/Sep 01/Oct Hydrograph of Myitnge River After Yewa Dam

14002500

1200 2000 Before Dam (1982) 1000 After Dam (2014) 1500

/sec) 800 After Dam (2014) 3

(m 600 1000

400 Flow 500 200

0 0 01/Jan 01/Feb 01/Mar 01/Apr 01/May 01/Jun 01/Jul 01/Aug 01/Sep 01/Oct 01/Nov 01/Dec 01/Jan 01/Feb 01/Mar 01/Apr 01/May 01/Jun 01/Jul 01/Aug 01/Sep 01/Oct 01/Nov 01/Dec

Many fluctuation Less frequent high flow pulse Seldom /Loss of floods Environmental Flow by Hydrological Approach

Initial Level Management Level

IHA Indicator of Hydrologic Tennant Software Alteration

Tessman

Flow Regime GEFC Alteration

Minimum Environmental Flow  Minimizing the degree of flow regime alteration is the key point to protect the ecosystem. Monthly Minimum Environmental Flow by Hydrological Approach Methods

1200 Natural Flow 1000 Tessman Tennant 800 GEFC 600 Release Flow

400

200

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

600

1200 500 Tessman

1000 Tennant Natural FLow 400 800 300 GEFC 600 Environmental Flow by GEFC 200 400 100 200

0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flow Regime Alteration

1200

1000 Pre-Dam

800 Post-Dam 600

400

200

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

The objective of environmental flows is not reproduced a natural flow regime in whole, but rather to achieve a flow regime that maintains the essential processes required to support healthy river ecosystems. Reservoir Simulation Model HEC‐ResSim

Scenario 1 ‐ existing operation policy Scenario 2 – to generate the power with full capacity based on rule curve Scenario 3 ‐ to generate the power with considering of the monthly minimum environmental flow requirement Reservoir Operation for Scenario‐1 Existing Operation Rule

 to check how flow regime was changed from natural flow under the existing operation policy Objective  to check the model performance under the existing operation policy.

In the existing condition, Yeywa power plant is connected to the national power grid and it is operated to meet the power demand in the region.

hydropower time series requirement rule Power Generation with Scenario ‐1

4000 Design - 3550 GWh 3500

3000

2500 80% SIM 2000 73% 73% 68% OBS 1500 68% 82% Design 71% 66% 1000 42% 500

0 2010 2011 2012 2013 2014 2015 2016 2017 2018

Simulated Energy – 2558.602 GWh Observed Energy – 2533.45 GWh Statistical Analysis for Model Performance (2010 to 2018)

2,000 Spill Spill 2500 1,500 R² = 0.8903 2000

1,000 1500 Flow (cms) Flow 1000 500 500 0 0 2010 2011 2012 2013 2014 2015 2016 2017 2018 -500 0 500 1000 1500 2000 2500 Yeywa Dam-Uncontrolled Outlet.Existing--0.Flow.1DAY YEYWA.OBSERVED.SPILL.1DAY Time of Simulation

700

600 Power Plant Flow Power Plant 500 800 R² = 0.9022 Flow 400 600

300 400 Flow (cms)Flow

200 200

100 0 0 200 400 600 800 0 2010 2011 2012 2013 2014 2015 2016 2017 2018 Yeywa Dam-Power Plant.Existing--0.Flow.1DAY YEYWA.OBSERVED.TURBINE FLOW.1DAY Time of Simulation

2,500 Outflow

2,000 3000 R² = 0.9123

Outflow 1,500 2000 Flow (cms) 1,000 1000

500 0 0 500 1000 1500 2000 2500 3000

0 2010 2011 2012 2013 2014 2015 2016 2017 2018 CP2.Existing--0.Flow.1DAY YEYWA.OBSERVED.OUTFLOW.1DAY Time of Simulation Reservoir Operation for Scenario‐2 to generate the power with full capacity within the rule curve without considering the environmental flow

Conservation Zone 185 180 175 170 165 160 155 150

Dead Level 01/Jan 01/Feb 01/Mar 01/Apr 01/Jun 01/Jul 01/May 01/Aug 01/Sep 01/Oct 01/Nov 01/Dec

200 190 180 170 Elev (m) 160 150

Power generation 27.8 Simulated Energy – 3271.977 GWh % increase Reservoir Operation for Scenario‐3 to generate the power with considering of the monthly minimum environmental flow requirement

First priority GEFC 1. Downstream control function rule EMC Management Perspective 2. Hydropower time series requirement rule A. Natural Not allow new water projects (dams, diversions, etc. ) B. Slightly Allow water supply schemes or Modified irrigation development

C. Multiple disturbances associated Moderately with the need for socio-economic Modified development, eg: dams, diversions, habitat modification and reduced water quality.

D. Largely Significantly disturbances Modified associated with water resources development, including dams, diversion, transfers, habitat modification and water quality degradation E. Seriously High human population density Modified and extensive water resources exploitation F. Critically This status is not acceptable from Modified the management perspective. Simulated Outflow

2,500

2,000

1,500 Flow (cms) 1,000

500

0 2010 2011 2012 2013 2014 2015 2016 2017 2018 EFlow.PandE-----0.Flow-MIN.1DAY CP2.PandE-----0.Flow.1DAY Time of Simulation

Power generation Simulated Energy – 2615.315 GWh 2.2 % increase 16

To assess flow regime alteration

1. Low flow Boundary condition 34 Environmental Flow 2. Extreme low flow 3. High flow 25th and 75th percentile of Component (EFC ) 4. Small flood natural flow 5. Large flood

1. Monthly water condition  ( N o  N e )  D i     100 2. Extreme water condition N (1,3,7,30,90 day min & max, zero day,  e  33 IHA base flow index) 0-33% = low alteration (L) 3. High and low pulse count/duration 34-67% = moderate alteration (M) 4. Water condition changes 68-100% = high alteration (H)

Pre Dam - Natural Flow (1981-2009) Outside boundary condition Post Dam - Simulated Outflow (2011-2018) Risks High alteration Summary Result for Three Scenarios Summary results showing the number of impact parameters for three scenarios Scenario-1 Scenario-2 Scenario-3 EFC parameters out of the 20 22 20 recommended range High alteration class in IHA 15 20 14 parameter Total risk 35 44 34

Comparison results for three scenarios Scenario Simulate Change Risk Change Energy Power Parameters Impact (GWh) Production (No) (%) 1 2558.602 Base case 35 Base case 2 3271.977 + 27.8 44 +9 3 2615.315 + 2.2 34 - 1 Conclusion

Among the three reservoir operation scenario, the most severe alteration is in the case of rule curve based operation (full operational capacity). The river channel, habitats and aquatic species could be negatively impacted due to the severe alteration.

In case of providing a monthly environmental flow did not significantly improve the alteration parameters from the current operational strategy but alteration level can slightly be reduced while increasing power production.

More investigation is needed to assess the impacts of the dam and its relationship for determining environmental flow recommendations.

For the sustainable water resource developments, it requires the developed reservoir operation rule that provide environmental flows to support the downstream riverine ecosystem by controlling the impact risk on the flow regime, and still maximizes energy production. Thanks for Your Attention