The document summarizes water resource development in Nepal's Koshi Basin. It finds that developing the basin's water resources through infrastructure like dams and hydropower projects could help meet future water demands under climate change and population growth scenarios. Modeling estimates the basin has over 8,000 million cubic meters of water storage potential and 29,000 gigawatt-hours of annual hydropower generation capacity. Water resource development could ease water stress, boost hydropower production to address Nepal's power shortage, and facilitate economic growth through regional power sharing agreements.

1. Cover slide option 1 Title
Water Resources
Development in the
Koshi Basin
Pennan Chinnasamy,
Luna Bharati, Ambika
Khadka, Utsav Bhattari.
p.Chinnasamy@cigar.org
Nepal Water Week
March 21, 2015
Photo: Hamish John Appleby / IWMI

2. INTRODUCTION
• IWMI
• IWMI Nepal
• Koshi basin
Taskent

3. WHY NEPAL?
• Nepal is one of the most water abundant countries in the world with total
mean annual runoff of 224 billion cubic meters (BCM) and per capita
water availability of 9,000 m3.
• There is large temporal and spatial variation in water availability. 85% of
rainfall is during the four monsoon months (June-Sept.)
• Water resources remain a particularly under-developed sector –Nepal is
currently only utilizing 7% of its annual water availability (14% in the
Koshi Basin). 24% of arable land is irrigated and out of 43,000 MW
hydropower potential, only 689 MW has been developed
• The impact of CC: what it means to future water availability and
development.
• The general perception is that if this resource is properly harnessed, it
would be the ticket out of poverty through economic growth mainly in the
hydropower and agriculture sectors.

4. IWMI – NEPAL PROJECTS
• Basin level water
management
• Impact of Climate Change
in the basin level
• Water resources and
vulnerability assessments
for entire Nepal
Bharati 2015

5. KOSHI BASIN
Objectives for the Koshi Basin
Analysis
• Resource assessment i.e. water
availability vs. water use at sub-
basin level (SWAT and WEAP)
• Impact of CC on river basin
hydrology
• Future basin development scenarios
– risks, vulnerabilities, opportunities
• Partners/Donors: ICIMOD, CIDA
CSIRO, World Bank, WLE

6. KOSHI BASIN (CONTD…)
• Koshi Basin (87,311 km2):
Transboundary basin-Largest
contributor to the Ganges river
• The elevation of the basin
varies from about 20m in the
plains in India to more than
8,000 m in the Great Himalayan
Range. Mount Everest (8,848
m) is also located in the basin.
• The basin in the Nepal part is
undeveloped but there are plans
to build multiple water
infrastructure.

7. HYDROLOGICAL MODEL: SWAT
INPUT DATA
Spatial: topography – Digital elevation map
Land use map
Soil map
Climate data: Time series Rainfall
Min and max temperature
Relative Humidity
Solar Radiation
Wind Speed
Hydrological Cycle is based on following
Water Balance Equation:


n
i
gwseepasurfdayot QwEQRSWSW
1
)(
Where,
SWt : Final soil water content (mm)
SWo : Initial soil water content (mm)
t : Time in days
Rday : Amount of precipitation on day I (mm)
Qsurf : Amount of surface runoff on day i (mm)
Ea : Amount of evapotranspiration on day i (mm)
wseep : Amount of percolation on day i (mm)
Qgw : Amount of return flow on day i (mm)

8. KOSHI WATER BALANCE (1998-2008)

9. CC ANALYSIS
RCP4.5
RCP8.5

10. Water Resources Development in
the Koshi
• Water resource development in the Koshi basin
• Need for water accounting model – WEAP
• Water storage potential in the basin
• Hydropower potential in the basin
• Future water demands and how infrastructure
development can aid

11. Water use status (demand and supply) in the Koshi Basin
• Collection of district
level water use and
demand data
• Estimate relationship
between water use
and demand
• Test against future
climate change
scenarios
• Aid in formulation of
better management
plans

12. Study Definition
Spatial Boundary System Components
Time Horizon Network Configuration
Evaluation
Water Sufficiency Ecosystem Requirements
Pollutant Loadings Sensitivity Analysis
Current Accounts
Demand Pollutant Generation
Reservoir Characteristics Resources and Supplies
River Simulation Wastewater Treatment
Scenarios
Demographic and Economic Activity
Patterns of Water Use, Pollution Generation
Water System Infrastructure
Hydropower
Allocation, Pricing and Environmental Policy
Component Costs
Hydrology
WEAP
Structure

15. Results for 2000 baseline year and
future Scenarios

16. Koshi Basin Water Supply Estimates
• Spatial Variations
• Temporal Variations

17. Water Demands in the basin
• Spatial Variations
• Temporal Variations
• Sectoral Demands
Subbasin level annual average water demand for the Baseline Scenario.

18. Water Demands in the basin
• Spatial Variations
• Temporal Variations
• Sectoral Demands
Subbasin level annual average water unmet demand for the Baseline Scenario.

19. Koshi Basin Water Resource
Development
• Based on JICA (1985,
2014)
• 7 Run of the River Type
• 4 Storage type
• High capacity
• Sapta Koshi
• Sun Koshi

20. www.iwmi.org
Water for a food-secure world
Results
Project Type
Available
Storage
(MCM)
Hydropower Generation (GWh)
Winter
Pre-
monsoon
Monsoon
Post-
monsoon
Annual
Arun III ROR - 8 33 60 8 109
Bhote Koshi ROR - 47 100 187 72 406
Lower Arun ROR - 364 524 695 348 1931
Sundarijal ROR - 27 61 113 21 222
Sun Koshi (HEP) ROR - 25 54 94 38 210
Tama Koshi ROR - 38 161 372 63 634
Upper Arun ROR - 169 279 451 225 1124
Dudh Koshi S 162 25 34 209 47 315
Sapta Koshi High
Dam
S 4420 761 2375 10716 2695 16547
Sun Koshi S 3040 242 501 3627 784 5154
Tamor S 760 81 553 2189 258 3081
Total 8382 1787 4676 18712 4558 29733
* ROR = Run-Of the-River, S = Storage

21. Total water storage
potential is 8382 MCM
Water demand under Baseline scenario with WRDs.
Demands and Flow Winter
Pre-
monsoon
Monsoon
Post-
monsoon
Annual
Baseline
Flow (m3
/s) 39 166 699 144 262
Domestic demand (MCM) 386 395 524 262 1566 (6 %)
Agricultural demand (MCM) 1890 6608 13489 2009 23996 (92 %)
Industrial demand (MCM) 105 107 142 71 424 (2 %)
Demand (MCM) 2380 7110 14154 2342 25986
Unmet demand (MCM) 273 370 0 17 660
* Brackets indicate percentage change from Baseline scenario. MCM- Million Cubic Meters

22. Past Current Future
Waterdemand
Time
Current trend
Higher water availability
Lower water availability
Lower stress/growth
Higher stress/growth
Future Scenarios

23. Seasonal variations in water demand and unmet demand under baseline, water resources
development, population growth, agricultural growth and industrial growth scenarios.
Scenarios
Winter
Pre-
monsoon
Monsoon
Post-
monsoon
Annual
Baseline
Demand (MCM) 2380 7110 14154 2342 25986
Unmet (MCM) 273 370 0 17 660
Population growth
Demand (MCM) 2727 9356 15521 2576 30180
Unmet (MCM) 337 555 0 27 920
Unmet Percent change (%) 23 50 0 60 39
Agricultural growth
Demand (MCM) 2406 8795 15215 2506 28922
Unmet (MCM) 370 543 0 58 970
Unmet Percent change (%) 36 47 0 241 47
Industrial growth
Demand (MCM) 2788 9419 15604 2618 30429
Unmet (MCM) 386 575 7 35 1003
Unmet Percent change (%) 41 55 0 106 52
* Unmet Percentage Change is the change in unmet demand between Baseline and Scenario.

24. Seasonal variations in water demand and unmet demand under baseline, water resources
development, population growth, agricultural growth and industrial growth scenarios.
Scenarios
Winter
Pre-
monsoon
Monsoon
Post-
monsoon
Annual
Baseline
Demand (MCM) 2380 7110 14154 2342 25986
Unmet (MCM) 273 370 0 17 660
Population growth
Demand (MCM) 2727 9356 15521 2576 30180
Unmet (MCM) 337 555 0 27 920
Unmet Percent change (%) 23 50 0 60 39
Agricultural growth
Demand (MCM) 2406 8795 15215 2506 28922
Unmet (MCM) 370 543 0 58 970
Unmet Percent change (%) 36 47 0 241 47
Industrial growth
Demand (MCM) 2788 9419 15604 2618 30429
Unmet (MCM) 386 575 7 35 1003
Unmet Percent change (%) 41 55 0 106 52
* Unmet Percentage Change is the change in unmet demand between Baseline and Scenario.
Total water
storage
potential is
8382 MCM !

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Total Hydropower
generation is 29000 GWh

27. www.iwmi.org
A water-secure world
Total annual volume
of water flowing into
India = 57405 MCM
Total annual volume
of water flowing into
India = 55138 MCM
Base Case : Year 2000 Case 1: Irrigated area = Irrigable area
Case 2: Hydropower generation + E-flows (B)
Total annual volume
of water flowing into
India = 56837 MCM

28. www.iwmi.org
Water for a food-secure world
Conclusion
• Study provides first estimates of sectoral water demands and unmet demands for
the basin.
• Study provides first estimates of the water storage and hydropower generation
potential for the basin.
• Water resource developments can ease climate vulnerability, water availability
issues and future water demands.
• Water resource developments can have huge hydropower generation potential
• Ease current and future National power shortage
• Enable economic growth by trans-boundary power sharing agreements
• Industrial developments