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Ayeyarwady River Basin Surface Water Resources Assessment

Speakers: Juanita Moolman, Geoffrey Adams Where is it?

Area: Chindwin R. • 414 000 km2

Ayeyarwady R. Main rivers: • Ayeyarwady River • Why?

SOBA (World Bank)

1 – Surface water resources

2 – Groundwater & WISDM

3 – Geomorphology & Sediments

4 – Biodiversity & Fisheries

5 – Socio-economics

6 – Local Consultations

State of the Basin Assessment (SOBA) How?

• provide a preliminary Baseline Source model which can be used to facilitate the ongoing assessment of the Ayeyarwady Basin and scenario building to evaluate future options and implications • contribute to the credible, evidence base that SOBA is developing for the ARB planning process • facilitate an understanding of any gaps in data collection as required for effective model building • provide a description of the hydrology of the ARB according to 5 identified Hydro-Ecological Zones (HEZ) and 13 identified sub-basins, with a focus on water availability and water use in the ARB What does it look like?

Hydro-Ecological Zones • 5

Tributary Sub-Basins • 13 What does it look like?

Climate Rainfall Himalayas • monsoonal • snow melt • cyclones

Central Dry Zone

Delta Temperature / PET What does it look like?

Land use/Land cover – IWMI 2014 • SOURCE functional units What does it look like?

~ 300 storages What does it look like?

Irrigation

• 77 rainfed cropping functional units • 84 SOURCE irrigator nodes • 17 lumped storages Domestic

• 36 SOURCE time series demands 95 Sub-catchments: • 27 Major Storages • 10 HP, 11 IrrigWorks, 6 MP • 5 HEZs, 13 sub-basins • 9 discharge sites The SOURCE model

Excluding: • Delta The SOURCE model

Rainfall-runoff modelling: • GR4J • GR4JSG plugin • Agricultural Runoff • Irrigator as FU • OpenWaterRR plugin The SOURCE model

Water use modelling • Domestic extractions • Irrigation extractions Thapanseik Reservoir • Irrigator Water User node • Beneficial areas • ‘Other’ areas • Storages • Major storages (hydropower, irrigation works, multipurpose Mu River Sub-basin • Lumped notional storages The SOURCE model

Baseline: Current • 2014 land use • 2016 storages • 1981 – 2016 climate The SOURCE model

Calibration at Pyay • 8% volume bias The SOURCE model

Pyay 8% volume bias Magway 6% volume bias -3% volume bias 3% volume bias 5% volume bias Hkamti -5% volume bias The SOURCE model

Challenges:

Data • Availability • Reliability

Operations The SOURCE model

Challenges:

• Discharge flow rates – 9 sites • Climate • Rainfall – 16 sites • PET – 1 site evaporation • Temperature – 15 sites (inc. flow sites) • Water use • crops • extractions • Storages • Catchment delineation The SOURCE model

Challenges: Rainfall (and Temperature) global data sets based on remote sensing • representative values • date range matching to observed (1986-2015)

• TRMM ~25km resolution – 1998-2013 • Princeton ~50km resolution – stops in 2012 • Watch Forcing data (EU) ~ Princeton res Aphrodite (stops 2007) • CHIRPS 5km res - (1981-2017) • Persianne The SOURCE model

Challenges: Rainfall at Hkamti The SOURCE model

Challenges: Rainfall Bias Error

CHIRPS APHRODITE Princeton PERSIANNE WATCH Site (%) (%) (%) (%) (%) Ayartaw 54% -17% 245% 142% 292% Bhamo -2% -23% -2% 10% -9% Gangaw 33% -27% 84% 81% 143% Hinthada -7% -14% 16% 5% 25% Hkamti -26% -32% -52% -35% -55% Katha -2% -22% 16% 42% 8% Magway 0% -27% 206% 66% 222% -6% -35% 33% 59% 50% Mawlaik -2% -17% 9% 34% 11% Minbu 13% -18% 247% 87% 265% Monywa 20% -17% 117% 131% 196% Myitkyina -4% -24% -13% 0% -14% Nyaung_Oo 31% -26% 257% 137% 297% Pakokku 26% -30% 205% 139% 268% Pyay -4% -17% 107% 44% 139% Sagaing 0% -36% 58% 71% 60% Ywatha 57% 3% 93% 129% 74% Overall 1% -23% 47% 36% 59% The SOURCE model

Challenges: Temperature – snowmelt and PET • Princeton • Watch

• 1981 – 2012

PET • Hargreaves method – only needs min and max temperature The SOURCE model

Challenges: Discharge flow rates – 9 sites

Five lines of evidence support problems with at least some historical recorded flow data: • The river in the Central Dry Zone should gain flow from groundwater (Len Drury per. Comm. June 2017), therefore flow at the downstream gauge should exceed the sum of the flows at the upstream gauges • The AWP Activity 1 investigation into the reliability of rating curves in the ARB – Katha and Nyaung U • Different ratings were developed for some gauges at different times • The apparent reduction in minimum dry season flow rates with time, especially at Sagaing ,which is more likely due to changes in rating curve (flow rate versus stage relationship) than a real reduction in flow rates • The reduction in recorded annual flows over time at Sagaing, compared with modelled. The next relatively reliable gauge downstream, Magway, shows no such trend to reducing annual flows The SOURCE model

Challenges: Discharge flow rates – 9 sites

Five lines of evidence support problems with at least some historical recorded flow data: • The river in the Central Dry Zone should gain flow from groundwater (Len Drury per. Comm. June 2017), therefore flow at the downstream gauge should exceed the sum of the flows at the upstream gauges • The AWP Activity 1 investigation into the reliability of rating curves in the ARB • The apparent reduction in minimum dry season flow rates with time, especially at Sagaing ,which is more likely due to changes in rating curve (flow rate versus stage relationship) than a real reduction in flow rates • The reduction in recorded annual flows over time at Sagaing, compared with modelled. The next relatively reliable gauge downstream, Magway, shows no such trend to reducing annual flows The SOURCE model

Challenges: Discharge flow rates – 9 sites

Five lines of evidence support problems with at least some historical recorded flow data: • The river in the Central Dry Zone should gain flow from groundwater (Len Drury per. Comm. June 2017), therefore flow at the downstream gauge should exceed the sum of the flows at the upstream gauges • The AWP Activity 1 investigation into the reliability of rating curves in the ARB – Katha and Nyaung U • Different ratings were developed for some gauges at different times

• The apparent reduction in minimum dry season flow rates with time, especially at Sagaing ,which is more likely due to changes in rating curve (flow rate versus stage relationship) than a real reduction in flow rates The SOURCE model

Challenges:

• Water use – agricultural and domestic • crop type Thapanseik Reservoir • cropping pattern • cropping areas • (FAO 2000! Agricultural Atlas) • extraction sources

Mu River Sub-basin The SOURCE model

Challenges:

• Storages Google Earth • location Thapanseik Reservoir • volume, area • operations!

Mu River Sub-basin The SOURCE model

Some outputs:

Rainfall

2000 2000 The SOURCE model

Some results: Seasons • Onset and duration of the wet season The SOURCE model

Some results: • Where does the flow come from? The SOURCE model

Some results: • Which are the most impacted sub-basins? The SOURCE model

Some results: • Which are the most impacted sub-basins?

40 38 23 8 9 5 The SOURCE model

Some results: Water balance – whole basin The SOURCE model

Some results: Water balance – Mu River sub-basin

Thapanseik Reservoir

Mu River Sub-basin The SOURCE model

Some results: Mu River sub-basin – patterns of use

Thapanseik Reservoir

Mu River Sub-basin The SOURCE model

Key findings:

• Stressed Sub-Basins • Data gaps • operational rules • return efficiencies • Monitoring recommendations • Data storage recommendations Understanding surface water resources in the Ayeyarwady River Basin

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