Water Systems Modeling for Ganga Basin Public Disclosure Authorized Public Disclosure Authorized
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Public Disclosure Authorized Water Systems Modeling for Ganga Basin Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized INRM Consultants Pvt. Ltd. New Delhi Submitted to the World Bank Water Systems Modeling for Ganga Basin Final Report CONTRACT NO. 7152490 Submitted to: World Bank Prepared by: INRM Consultants Pvt. Ltd. In Association with: Prof. A. K. Gosain Professor, Department of Civil Engineering Indian Institute of Technology (IIT) Delhi Prof. R. Srinivasan Director of Spatial Sciences Laboratory Professor of Ecosystem Science and Management and Biological and Agricultural Engineering Texas A&M University Table of Contents Executive Summary ............................................................................................................... 1 1. Introduction .................................................................................................................... 6 1.1. About the Ganga basin ............................................................................................ 6 2. Scope of the study .......................................................................................................... 8 3. Methodology .................................................................................................................. 8 3.1. Brief Description of the Soil and Water Assessment Tool (SWAT) Model ........... 8 3.2. Advantages of the SWAT model ........................................................................... 10 3.3. Development of hydrologic model for the Ganga Basin ....................................... 11 3.3.1. Data Requirement for Modelling ................................................................... 11 3.3.1.1. Spatial Data ............................................................................................. 11 3.3.1.2. Dynamic Data ......................................................................................... 11 3.3.2. Model Performance ........................................................................................ 12 3.4. Mapping the Ganga System................................................................................... 13 3.4.1.1. Basin Delineation – Ganga Basin ........................................................... 14 3.4.1.2. Watershed (sub-basin) Delineation – Ganga Basin ................................ 15 3.4.1.3. Land Cover/Land Use Layer – Ganga Basin .......................................... 15 3.4.1.4. Soil Layer– Ganga Basin ........................................................................ 17 3.4.1.5. Hydro-Meteorological and Water resources structures data................... 19 4. Baseline (Scenario A) Analysis ................................................................................... 20 4.1.1.1. SWAT model setup - Scenario A ........................................................... 22 4.2. SWAT Model Performance for Ganga Basin ........................................................ 35 5. Scenarios Analysis ....................................................................................................... 49 5.1.1. Average monthly comparisons for the Kosi at the confluence of Kosi with main Ganga with and without upstream dams in Nepal .............................................. 56 6. Limitations of the Study and Future Prospects ............................................................ 63 6.1. Assumptions .......................................................................................................... 63 6.2. Data Limitations .................................................................................................... 63 6.3. Model limitations .................................................................................................. 64 6.4. Future Studies ........................................................................................................ 65 Appendix I .............................................................................................................................. 1 Distributed Behaviour of the SWAT model ...................................................................... 1 Brief Theoretical Basis of the SWAT model ..................................................................... 1 Brief Description of ArcSWAT Interface .......................................................................... 8 Appendx II - Climate Change Scenarios ................................................................................ 9 Regional Climate Scenarios for India Using PRECIS ....................................................... 9 The Hydrologic Simulation with Climate Change Scenarios ...................................... 11 Spatial distribution of water balance components ................................................... 16 Appendx III - Ganga Basin Knowledgebase ........................................................................ 21 Features ........................................................................................................................ 21 Technology Used ......................................................................................................... 21 Interface........................................................................................................................ 21 List of Tables Table 1 Elevation Summary – Ganga Basin ........................................................................ 14 Table 2 Landuse Categories – Ganga Basin ........................................................................ 16 Table 3 Soil Type – Ganga Basin ........................................................................................ 18 Table 4 Scenarios used in the study ..................................................................................... 20 Table 5 SWAT output comparison Locations and model efficiency parameters ................ 37 Table i Summaries of IPCC SRES Scenarios ...................................................................... 10 Table ii Trend in water balance for IPCC SRES A1B Baseline and Mid Century climate scenarios ....................................................................................................................... 14 Table iii Water Balance Components as % of rainfall for IPCC SRES A1B Baseline, Mid and End Century climate scenarios .............................................................................. 14 List of Figures Figure 1 Ganga Basin Index Map .......................................................................................... 6 Figure 2 Digital Elevation Model of Ganga Basin ............................................................. 13 Figure 3 Automatically delineated Basins of Ganga Basin along with Drainage network .. 14 Figure 4 Ganga Basin subbasin delineation using DEM .................................................... 15 Figure 5 Landuse of Ganga Basin ........................................................................................ 16 Figure 6 Soils of Ganga Basin ............................................................................................. 18 Figure 7 Weather Grids along with Water resources structure locations of Ganga Basin ... 19 Figure 8 Annual Water Balance Components – Ganga ....................................................... 23 Figure 9 Average Monthly Water Balance Component (Ganga)......................................... 24 Figure 10 Average Annual Water Balance Component (Ganga) ......................................... 25 Figure 11 Spatial distribution of Average Annual Precipitation (Ganga) ............................ 26 Figure 12 Spatial distribution of Average Annual Snowmelt & Snow hydrology .............. 27 Figure 13 Spatial distribution of Average Annual Water Yield (Ganga) ............................ 29 Figure 14 Spatial distribution of Average Annual Actual Evapotranspiration (Ganga) ...... 30 Figure 15 Spatial distribution of Average Annual Ground Water Flow (Ganga) ................ 31 Figure 16 Spatial distribution of Average Annual Irrigation Water Demand (Ganga) ........ 32 Figure 17 Spatial distribution of Average Annual Sediment Yield (Ganga) ....................... 33 Figure 18 Spatial distribution of Average Annual BOD Load (Ganga) .............................. 34 Figure 19 Stream flow Gauge Locations used for SWAT model verification ..................... 36 Figure 20 SWAT output comparison Locations and model efficiency parameters ............. 38 Figure 21 Spatial Variation of Annual average precipitation and the change in annual precipitation for high, average and low rainfall – Scenario A (Baseline) .................... 49 Figure 22 Spatial Variation of Annual average water yield and the change in annual yield for high, average and low rainfall year ........................................................................ 50 Figure 23: Average Annual Percent Change of BOD concentration from Scenario A to C 51 Figure 24: Average Annual Percent Change of Sediment load from Scenario A to C ........ 52 Figure 25 Average monthly BOD concentration during Monsoon and non monsoon months for high, average and low rainfall year (baseline-Scenario A) .................................... 53 Figure 26 Change (%) in Annual BOD Concentration from Scenario A to Scenario D50 . 55 Figure 27 Change (%) in Annual Sediment Load from Scenario A to Scenario D50 ......... 56 Figure 28 Locations for comparison of flow........................................................................ 57 Figure