The document summarizes a study that used the SWAT hydrological model to assess the impact of climate change on the Ganga River Basin in India. Some key findings include:
- Modeling results showed increases in precipitation but decreases in runoff and evapotranspiration for the GHG climate scenario compared to the control scenario.
- Annual peak discharges were higher for many sub-basins under the GHG scenario, with some exceeding thresholds of 10,000, 20,000 and 30,000 cumecs.
- The flow duration curve for the Ganga River showed lower dependable flows under the GHG scenario compared to the control scenario.
- Further work is needed to incorporate glacier data, existing
1. Impact of Climate Change on
Ganga River Basin
A. K. Gosain
Professor of Civil Engineering
Indian Institute of Technology Delhi
2. Presentation layout
Methodology used – SWAT model
SWAT implementation on Indian basins
for climate change impact assessment
Detailed results of Ganga basin
Gaps in the study
3. SWAT Hydrological model
SWRRB - Early 80's -Modified CREAMS
SWAT - Early 90's -Modified SWRRB
Reach Routing Structure
Flexible Watershed
Configurations
TAES-IIT Delhi MoA - 1996, to
collaborate in further development of
the model
4. Model Objectives
Predict the impact of man-made
changes & management practices
Predict the impact of global warming
water, sediment, nutrient and pesticide
yields
generate alternate scenarios
conduct vulnerability assessment
5. Can map wide range of features
Pond & reservoir storage
Crop growth & irrigation
Groundwater flow
Reach routing
Nutrient & pesticide loading
Water transfer
6. Major inputs
Weather
Daily Precipitation
Max - Min Temperature
Solar Radiation
Wind Speed & Relative Humidity
Terrain
Landuse
Soil
7. Crop Growth
Generic model - Parameterized by plant
database used by EPIC and WEPP
Phenological Development - Daily heat
unit accumulation
Potential Growth - Interception of solar
radiation (LAI, solar radiation)
Growth Constraints - Water, temperature,
nitrogen & phosphorous stress
8. Model Output
Model outputs include all the water balance
component at various levels i.e., basin, subbasin or
watershed level and at intervals of daily, monthly or
annual
surface runoff
evapotranspiration
lateral flow
recharge
percolation
sediment yield
Nutrients
9. Initial National Communication to
UNFCCC
Coordinated by MoEF
A large number of groups involved to
undertake studies in various sectors
Water Resources entrusted to IIT Delhi
The communication has been made by the
MoEF to UNFCC
10. Objectives of the Study
To quantify the impact of the climate
change on the water resources of the
country
Identify Hotspots
Identify Adaptation & Coping strategies
11. Data Used for Modeling
Contour: 100 m interval - 1:250,000
DEM: 1km grid, generated using ArcView
Land use: 1:2M USGS
Soil: 1:5M FAO
Drainage: 1:250,000
Weather: Data generated by the “Hadley
Centre for Climate Prediction” U.K. at a
resolution of 0.44° X 0.44° latitude by
longitude (HadRM2) from IITM, Pune
13. Annual mean water balance for Control and GHG climate
scenarios in different river basins
Trends in Waterbalance Components (Control and GHG Climate Scenarios)
1800
1600
1400
1200
Value (mm)
1000
800
600
400
200
0
Cauvery Brahmani Godavari Krishna Luni Mahanadi Mahi Narmada Pennar Tapi Ganga Sabarmati
Rain (Control) Rain (GHG) Runoff (Control) Runoff (GHG) AET (Control) AET (GHG)
14. Percent change in mean annual water balance
for Control and GHG climate scenarios
Change from Current to GHG Scenario (%)
40
Rainfall Runoff ET
20
0
-20
-40
-60
-80
Krishna
Luni
Tapi
Mahi
Ganga
Cauvery
Pennar
Brahmani
Godavari
Narmada
Mahanadi
Sabarmati
River Basins
15. Assumptions and Coarseness of
the Data Used
Daily RCM data not reconciled for its
accuracy
Landuse has been assumed to be same
Water bodies including reservoirs could
not be incorporated at this stage due to
lack of data
16. Ganga River Basin Annual water balance
components
1800 1800
Control Scenario Precipitation Precipitation
GHG Scenario
1600 ET 1600 ET
Water Yield Water Yield
1400 1400
1200 1200
Value (mm)
Value (mm)
1000 1000
800 800
600 600
400 400
200 200
0 0
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
Year Year
17. Monthly water balance components
for Ganga river basin
350 350
Control Precipitation GHG Precipitation
300 Scenario ET 300 ET
Water Yield Water Yield
250 250
Value (mm)
Value (mm)
200 200
150 150
100 100
50 50
0 0
Jun
Nov
Jul
May
Jan
Aug
Oct
Mar
Apr
Feb
Dec
Sep
Jun
Nov
Jul
May
Jan
Aug
Oct
Mar
Apr
Dec
Feb
Sep
Year Year
18. Change in Monthly water balance
components for Ganga river basin
40 Precipitation
Change in monthly water balance for
Control and GHG climate scenarios ET
30 Water Yield
20
Value (mm)
10
0
May
Mar
Nov
Jan
Jun
Aug
Jul
Apr
Feb
Sep
Oct
Dec
-10
-20 180
Change (%) in monthly water balance Precipitation
160 for Control and GHG climate scenarios ET
-30 140 Water Yield
Year 120
100
Value (%)
80
60
40
20
0
Jul
May
Nov
Jan
Jun
Mar
Dec
Oct
Feb
Aug
Sep
Apr
-20
-40
Year
20. Ganga River – Annual Peak
18000 18000
Control Scenario
Annual daily peak discharge
Annual daily peak discharge
Subbasin 11 Subbasin 11 GHG Scenario
16000 16000
14000 14000
12000 12000
(cumecs)
(cumecs)
10000 10000
8000 8000
6000 6000
4000 4000
2000 2000
0 0
1 3 5 7 9 11 13 15 17 19 1 3 5 7 9 11 13 15 17 19
Year Num ber Year Num ber
45000 45000
Control Scenario
Annual daily peak discharge
Annual daily peak discharge
Subbasin 23 Subbasin 23 GHG Scenario
40000 40000
35000 35000
30000 30000
(cumecs)
25000 (cumecs) 25000
20000 20000
15000 15000
10000 10000
5000 5000
0 0
1 3 5 7 9 11 13 15 17 19 1 3 5 7 9 11 13 15 17 19
Year Num ber Year Num ber
21. Events exceeding arbitrary thresholds in
Ganga River Basin
Discharge Control GHG Control GHG
(cumecs)
Ganga Subbasins Sub11 Sub11 Sub23 Sub23
Discharge>10000 6 7
>20000 1 5
Discharge>12000 1 6
>30000 0 2
22. Flow Duration Curve for Ganga River
for Control and GHG scenarios
Ganga River - Flow Duration Curve
100000
Control
10000 GHG
1000
100
Flow (Cumecs)
10
1
0.1
0.01
0.001
0.0001
0.00001
0 10 20 30 40 50 60 70 80 90 100
% of time flow equal or exceeded
Dependa 25% 50% 75% 90%
ble Flow
(cumecs)
Control 4648 716 12.88 0.4394
GHG 3649 754.5 50.5 5.323
Scenario
23. Future Work Required
Incorporation of the data on glaciers
Mapping and incorporation of present
manmade interventions
Generation of coping strategies and
scenarios
Quantifying the uncertainties of the
predictions