Water availability, demand and adaptation option assessment of the Ganges Basin under climate ...

95 Pages·2015·9.46 MB·English

Water availability, demand and
adaptation option assessment of the
Ganges Basin under climate change
Technical Report – Hydrological Modelling
Koshi, Tamkoshi, Dudhkoshi, Tamor Basins and Ganga

Basin

Department of Civil Engineering
Indian Institute Of Technology, Delhi
Hauz Khas, New Delhi 110016, India
Water availability, demand and
adaptation option assessment of the
Ganges Basin under climate change
Technical Report – Hydrological Modelling
Koshi, Tamkoshi, Dudhkoshi, Tamor Basins and Ganga

Basin

Contract no:
Project Funded by:
November 2013

Department of Civil Engineering
Indian Institute Of Technology, Delhi
Hauz Khas, New Delhi 110016, India
Table of Contents
TABLE OF CONTENTS .......................................................................................................................... I
LIST OF FIGURES .............................................................................................................................. III
LIST OF TABLES ................................................................................................................................ V
EXECUTIVE SUMMARY ...................................................................................................................... VI
CHAPTER 1 - INTRODUCTION ........................................................................................................ 8
THE KOSHI RIVER BASIN PROFILE ......................................................................................................... 8
PHYSIOGRAPHY ........................................................................................................................................... 8
CLIMATE .................................................................................................................................................... 9
SOILS ....................................................................................................................................................... 10
LANDUSE .................................................................................................................................................. 10
MAJOR TRIBUTARIES .................................................................................................................................. 10
IRRIGATION .............................................................................................................................................. 10
CHAPTER 2 - SWAT MODEL SETUP FOR THE KOSHI BASIN AND CURRENT BASELINE SIMULATION . 12
METHODOLOGY ............................................................................................................................. 12
SOIL AND WATER ASSESSMENT TOOL (SWAT) MODEL ................................................................................... 12
Advantages of the SWAT model ........................................................................................................... 13
DEVELOPMENT OF HYDROLOGIC MODEL FOR THE KOSHI RIVER BASIN .......................................................... 15
Model Performance .............................................................................................................................. 16
MAPPING THE KOSHI RIVER BASIN ................................................................................................................ 18
Basin Demarcation ................................................................................................................................ 18
Watershed (sub-basin) Delineation ...................................................................................................... 19
Land Cover/Land Use Layer .................................................................................................................. 20
Soil Layer ............................................................................................................................................... 21
Hydro-Meteorological and Water resources structures data ............................................................... 22
SWAT MODEL PERFORMANCE FOR THE KOSHI BASIN ..................................................................................... 24
THE HYDROLOGIC SIMULATION WITH OBSERVED WEATHER ............................................................................. 27
Temporal distribution of major water balance components................................................................ 28
Flow Duration Curve ............................................................................................................................. 30
CHAPTER 3 - CLIMATE CHANGE SCENARIOS USING BCCR IPCC AR5 RCP WEATHER DATA .............. 36
CLIMATE CHANGE DATA USED FOR HYDROLOGICAL MODELLING ....................................................................... 36
THE HYDROLOGIC SIMULATION WITH CLIMATE CHANGE SCENARIOS .................................................................. 37
Seasonal Change in water balance components for RCP 4.5 and RCP 8.5 Scenarios ........................... 42
IMPACT ASSESSMENT ...................................................................................................................... 44
DROUGHT ANALYSIS .................................................................................................................................. 44
FLOOD ANALYSIS ....................................................................................................................................... 46
Average peak discharge at 99th percentile............................................................................................ 47
i
Flow Duration Curve and Impact on Reservoirs ................................................................................... 47
LIMITATIONS OF THE STUDY .............................................................................................................. 53
ASSUMPTIONS .......................................................................................................................................... 53
Data Limitations .................................................................................................................................... 53
Model limitations .................................................................................................................................. 54
CHAPTER 4 - CLIMATE CHANGE SCENARIOS USING - DELTA CHANGE METHOD WEATHER DATA ... 56
CLIMATE CHANGE DATA USED FOR HYDROLOGICAL MODELLING ....................................................................... 56
THE HYDROLOGIC SIMULATION WITH CLIMATE CHANGE SCENARIOS .................................................................. 56
Flow Duration Curve and Impact on dependable flow for Koshi Basin ................................................ 56
Climate Change Impact on flow for Ganga Basin.................................................................................. 66
CHAPTER 5 - FUTURE DEMAND SCENARIOS AND IMPACT OF CLIMATE CHANGE ........................... 82
FUTURE WATER DEMAND SCENARIO ............................................................................................................ 82
THE HYDROLOGIC SIMULATION WITH CLIMATE CHANGE SCENARIOS .................................................................. 82
Flow Duration Curve and Impact on dependable flow for Koshi Basin ................................................ 83
CHAPTER 5 - SUMMARY AND CONCLUSIONS ............................................................................... 93
ii
List of Figures
FIGURE 1 : GEOGRAPHICAL CONTEXT OF THE KOSHI RIVER BASIN ........................................................................ 9
FIGURE 2 : STUDY AREA - THE KOSHI BASIN ......................................................................................................... 15
FIGURE 3 : DIGITAL ELEVATION MODEL OF THE KOSHI RIVER BASIN ................................................................... 18
FIGURE 4 : BASIN DELINEATION USING DEM FOR THE KOSHI RIVER BASIN ......................................................... 19
FIGURE 5 : SUB BASIN DELINEATION USING DEM FOR THE KOSHI RIVER BASIN ................................................. 19
FIGURE 6 : LANDUSE MAP FOR THE KOSHI RIVER BASIN...................................................................................... 20
FIGURE 7 : SOIL MAP FOR THE KOSHI RIVER BASIN .............................................................................................. 21
FIGURE 8 : : METEOROLOGICAL LOCATIONS FOR THE KOSHI RIVER BASIN ......................................................... 22
FIGURE 9 : STREAM FLOW MEASUREMENT LOCATIONS MAP OF KOSHI RIVER BASIN ........................................ 23
FIGURE 10 : SWAT OUTPUT COMPARISON LOCATIONS AND MODEL EFFICIENCY PARAMETERS FOR THE KOSHI
BASIN ........................................................................................................................................................... 26
FIGURE 11 : SIMULATED AVERAGE WATER BALANCE COMPONENTS FOR KOSHI RIVER BASIN .......................... 28
FIGURE 12 : SIMULATED AVERAGE MONTHLY WATER BALANCE COMPONENTS FOR KOSHI RIVER BASIN ......... 29
FIGURE 13 : SIMULATED AVERAGE ANNUAL WATER BALANCE COMPONENTS FOR KOSHI RIVER BASIN ........... 30
FIGURE 14 : FLOW DURATION CURVES AT VARIOUS LOCATIONS ON KOSHI RIVER BASIN .................................. 31
FIGURE 15 :CLIMATE CHANGE GRID LOCATIONS IN THE KOSHI RIVER BASIN ...................................................... 37
FIGURE 16 ANNUAL WATER BALANCE COMPONENTS FOR BL AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 4.5)
FOR THE KOSHI RIVER BASIN ....................................................................................................................... 38
FIGURE 17 ANNUAL WATER BALANCE COMPONENTS FOR BL AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 8.5)
FOR THE KOSHI RIVER BASIN ....................................................................................................................... 39
FIGURE 18 MONTHLY WATER BALANCE COMPONENTS FOR BL AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 4.5
AND RCP 8.5) FOR THE KOSHI RIVER BASIN ................................................................................................. 40
FIGURE 19 SPATIAL DISTRIBUTION OF CHANGE IN WATER BALANCE COMPONENTS TOWARDS MID CENTURY
(IPCC AR5 RCP 4.5 AND 8.5) FOR THE KOSHI RIVER BASIN .......................................................................... 41
FIGURE 20 SEASONAL CHANGE IN WATER BALANCE (MM) EXPRESSED AS PERCENT CHANGE IN PRECIPITATION
(IPCC AR5 RCP 4.5 AND RCP 8.5) FOR THE KOSHI RIVER BASIN ................................................................... 43
FIGURE 21 CHANGE IN SPATIAL DISTRIBUTION OF SOIL MOISTURE DEFICIT WEEKS FOR BL AND MC SCENARIOS
(IPCC AR5 RCP 4.5) FOR THE KOSHI RIVER BASIN – SOUTH WEST MONSOON (JJAS) .................................. 45
FIGURE 22 CHANGE IN SPATIAL DISTRIBUTION OF SOIL MOISTURE DEFICIT WEEKS FOR BL AND MC SCENARIOS
(IPCC AR5 RCP 8.5) FOR THE KOSHI RIVER BASIN – SOUTH WEST MONSOON (JJAS) ................................ 46
FIGURE 23 SPATIAL VARIATION IN CHANGE IN STREAM DISCHARGE AT 99TH PERCENTILE FOR BL AND MC
CLIMATE SCENARIOS (IPCC AR5 RCP 4.5 AND RCP 8.5) FOR THE KOSHI RIVER BASIN ................................ 47
FIGURE 24 LOCATIONS WHERE DEPENDABLE FLOW IS ASSESSED FOR BL AND MC CLIMATE SCENARIOS (IPCC
AR5 RCP 4.5 AND RCP 8.5) FOR THE KOSHI RIVER BASIN ............................................................................ 48
FIGURE 25 DEPENDABLE FLOW IS ASSESSED FOR BL AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 4.5 AND RCP
8.5) FOR SEVEN LOCATIONS IN KOSHI RIVER BASIN .................................................................................... 49
FIGURE 26 LOCATIONS WHERE DEPENDABLE FLOW IS ASSESSED FOR BL AND MC CLIMATE SCENARIOS (IPCC
AR5 RCP 4.5 AND RCP 8.5) FOR THE KOSHI RIVER BASIN ............................................................................ 57
FIGURE 27 SIMULATED DEPENDABLE FLOW FOR OBSERVED AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 4.5
AND RCP 8.5, STATISTICAL DOWNSCALING) FOR SEVEN LOCATIONS IN KOSHI RIVER BASIN ..................... 58
FIGURE 28 SIMULATED 75% DEPENDABLE FLOW FOR OBSERVED AND MC CLIMATE SCENARIOS (IPCC AR5 RCP
4.5 AND RCP 8.5, STATISTICAL DOWNSCALING) FOR SEVEN LOCATIONS IN KOSHI RIVER BASIN ............... 62
FIGURE 29 LOCATIONS WHERE DEPENDABLE FLOW IS ASSESSED FOR BL AND MC CLIMATE SCENARIOS (IPCC
AR5 RCP 4.5 AND RCP 8.5, STATISTICAL DOWNSCALING) FOR THE GANGA RIVER BASIN .......................... 66
FIGURE 30 SIMULATED DEPENDABLE FLOW (BASED ON AVERAGE MONTHLY FLOWS) FOR OBSERVED CLIMATE
AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 4.5 AND RCP 8.5, STATISTICAL DOWNSCALING) AT VARIOUS
LOCATIONS IN GANGA RIVER BASIN ............................................................................................................ 67
iii
FIGURE 31 SIMULATED 75% DEPENDABLE FLOW FOR OBSERVED AND MC CLIMATE SCENARIOS (IPCC AR5 RCP
4.5 AND RCP 8.5, STATISTICAL DOWNSCALING) FOR VARIOUS LOCATIONS IN GANGA RIVER BASIN ......... 77
FIGURE 32 LOCATIONS OF PLANNED RESERVOIRS AND LOCATIONS WHERE WHERE DEPENDABLE FLOW IS
ASSESSED FOR BL AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 4.5 AND RCP 8.5) FOR THE KOSHI RIVER
BASIN ........................................................................................................................................................... 83
FIGURE 33 SIMULATED DEPENDABLE FLOW FOR OBSERVED AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 4.5
AND RCP 8.5, STATISTICAL DOWNSCALING) AT MULGHAT IN KOSHI RIVER BASIN ..................................... 84
FIGURE 34 SIMULATED DEPENDABLE FLOW FOR OBSERVED AND MC CLIMATE SCENARIOS (IPCC AR5 RCP 4.5
AND RCP 8.5, STATISTICAL DOWNSCALING) AT CHARATA IN KOSHI RIVER BASIN ...................................... 85
FIGURE 35 SIMULATED 75% DEPENDABLE FLOW FOR OBSERVED BAU, OBSERVED AND MC CLIMATE
SCENARIOS (IPCC AR5 RCP 4.5 AND RCP 8.5, STATISTICAL DOWNSCALING) FOR MULGHAT AND CHATARA
IN KOSHI RIVER BASIN WITH 3 DEMAND SCENARIOS .................................................................................. 88

iv
List of Tables
TABLE 1 ELEVATION SUMMARY –STUDY AREA .................................................................................................... 18
TABLE 2 LANDUSE CATEGORIES –OF THE KOSHI RIVER BASIN ............................................................................. 20
TABLE 3 SOIL TEXTURE OF THE KOSHI RIVER BASIN ............................................................................................. 21
TABLE 4 STREAM FLOW MEASUREMENT STATIONS –KOSHI RIVER BASIN .......................................................... 22
TABLE 5 SWAT OUTPUT COMPARISON LOCATIONS AND MODEL EFFICIENCY PARAMETERS .............................. 25
TABLE 6 FLOW DEPENDABILITY – SUB-BASINS OF KOSHI RIVER BASIN ............................................................... 30
TABLE 7: OVERVIEW OF REPRESENTATIVE CONCENTRATION PATHWAYS (RCPS) ADOPTED BY IPCC AR5 .......... 36
TABLE 8 SUMMARY OF SEASONAL CHANGE IN WATER BALANCE (MM) EXPRESSED AS PERCENT CHANGE IN
PRECIPITATION FOR THE STUDY AREA (BASELINE TO MID CENTURY) – RCP 4.5 AND RCP 8.5 ................... 42
TABLE 9 DEPENDABLE FLOW AT VARIOUS LOCATIONS (MCM) FOR IPCC AR5 RCP 4,5 AND RCP 8.5 SCENARIOS
(BASELINE, AND MID CENTURY) .................................................................................................................. 52
TABLE 10 MODEL SELECTION BASED ON 10TH AND 90TH PERCENTILE VALUES OF PROJECTED CHANGES IN P AND
T FROM 1961-1990 TO 2021-2050............................................................................................................... 56
TABLE 11 DEPENDABLE FLOW AT VARIOUS LOCATIONS (CMS) FOR IPCC AR5 RCP 4,5 AND RCP 8.5 SCENARIOS
(BASELINE, AND MID CENTURY) .................................................................................................................. 61
TABLE 12 DEPENDABLE FLOW AT VARIOUS LOCATIONS ON GANGA (CMS) FOR IPCC AR5 RCP 4,5 AND RCP 8.5
SCENARIOS (BASELINE, AND MID CENTURY) ............................................................................................... 74
TABLE 13 DETAILS OF THE FUTURE DEVELOPMENT PROJECTS ............................................................................ 82
TABLE 14 SCENARIOS USED IN THE STUDY ........................................................................................................... 82
TABLE 15 DEPENDABLE FLOW AT MULGHAT AND CHATARA LOCATIONS (CMS) FOR IPCC AR5 RCP 4,5 AND RCP
8.5 SCENARIOS (BASELINE, AND MID CENTURY) FOR 3 DEMAND SCENARIOS ............................................ 87

v
Executive Summary

vi
DRAFT FINAL REPORT [SWAT Hydrological Modelling]]

Chapter 1

Introduction
Chapter 1 | IIT Delhi.
DRAFT FINAL REPORT [SWAT Hydrological Modelling]]

CThhe Kaopshti eRirve 1r B a-s iInn prtorfiole duction
The Koshi River drains the southern slopes of the Himalayas in Nepal and is formed by three main
streams: the Tamur Koshi originating from Mt. Kanchenjunga in the east, Arun Koshi from Mt.
Everest in Tibet, and Sun Koshi from Mt. Gosainthan farther west. From their confluence north of
the Chatra Gorge onwards, the Koshi River is known as Saptakoshi . The trans-boundary river crosses
northern Bihar branching off into several channels and joins the Ganga near Kursela in the Katihar
district1.
The eight tributaries of the basin upstream the Chatra Gorge include from east to west2:
• Tamur River with an area of 6,053 km2 (2,337 sq mi) in eastern Nepal;
• Arun River with an area of 33,500 km2 (12,900 sq mi), most of which is in Tibet;
• Sun Koshi with an area of 4,285 km2 (1,654 sq mi) in Nepal and its northern tributaries
Dudh Koshi, Likhu Khola, Tama Koshi, Bhote Koshi and Indravati.
The three major tributaries meet at Triveni, from where they are called Sapta Koshi meaning Seven
Rivers. After flowing through the Chatra Gorge the Sapta Koshi is controlled by the Koshi Barrage
before it drains into the Gangetic plain.
The total drainage area of the Koshi River is 74,030 km2 out of which 11,410 km2 lies in India and the
rest 62,620 km2 lies in Tibet and Nepal3.
Physiography
The Koshi River catchment covers six geological and climatic belts varying in altitude from above
8,000 to 95 m comprising the Tibetan plateau, the Himalayas, the Himalayan mid-hill belt, the
Mahabharat Range, the Siwalik Hills and the Terai. In the Himalayas, eight peaks over 8,000 m, 36
glaciers and 296 glacier lakes are located in the catchment area4. The Koshi River basin borders the
Tsangpo River basin in the north, the Mahananda River basin in the east, the Ganges Basin in the
south and the Gandaki River basin in the west5 (Figure 1).

1 http://en.wikipedia.org/wiki/Koshi_River
2 Nepal, S. (2012). Evaluating upstream downstream linkages of Hydrological Dynamics in the Himalayan
Region. Dissertation, Faculty of Chemical and Earth Sciences of the Friedrich-Schiller-University Jena
3 http://fmis.bih.nic.in
4 Bajracharya, S. R., Mool, P. K., Shrestha, B. R. (2007). Impact of climate change on Himalayan glaciers and
glacial lakes: case studies on GLOF and associated hazards in Nepal and Bhutan. International Centre for
Integrated Mountain Development (ICIMOD)
5 Jain, S. K.; Agarwal, P. K.; Singh, V. P. (2007). Hydrology and water resources of India. Dordrecht: Springer. pp.
358–359. ISBN 978-1-4020-5179-1.
8 Chapter 1 - Introduction | INRM Consultants