Impact of Climate Change on Ganga River Basin

A. K. Gosain

Professor of Civil Engineering

Indian Institute of Technology Delhi

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

SWAT Hydrological model

� SWRRB - Early 80's -Modified CREAMS

� SWAT - Early 90's -Modified SWRRBReach Routing StructureFlexible Watershed

Configurations

� TAES-IIT Delhi MoA - 1996, to collaborate in further development of the model

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

Can map wide range of features

� Pond & reservoir storage

� Crop growth & irrigation

� Groundwater flow

� Reach routing

� Nutrient & pesticide loading

� Water transfer

Major inputs

� Weather � Daily Precipitation

� Max - Min Temperature

� Solar Radiation

� Wind Speed & Relative Humidity

� Terrain

� Landuse

� Soil

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

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

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

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

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

River Basins Modeled

Annual mean water balance for Control and GHG climate scenarios in different river basins

Trends in Waterbalance Components (Control and GHG Climate Scenarios)

0

200

400

600

800

1000

1200

1400

1600

1800

Cauvery Brahmani Godavari Krishna Luni Mahanadi Mahi Narmada Pennar Tapi Ganga Sabarmati

Valu

e (

mm

)

Rain (Control) Rain (GHG) Runoff (Control) Runoff (GHG) AET (Control) AET (GHG)

Percent change in mean annual water balance for Control and GHG climate scenarios

-80

-60

-40

-20

0

20

40

Mah

an

ad

i

Bra

hm

an

i

Gan

ga

Go

davari

Cau

very

Narm

ad

a

Tap

i

Kri

sh

na

Pen

nar

Mah

i

Lu

ni

Sab

arm

ati

River Basins

Ch

an

ge

fro

m C

urr

en

t to

GH

G S

ce

na

rio

(%

)

Rainfall Runoff ET

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

Ganga River Basin Annual water balance components

0

200

400

600

800

1000

1200

1400

1600

1800

19

81

19

82

19

83

19

84

19

85

19

86

19

87

19

88

19

89

19

90

19

91

19

92

19

93

19

94

19

95

19

96

19

97

19

98

19

99

20

00

Year

Va

lue

(m

m)

PrecipitationETWater Yield

Control Scenario

0

200

400

600

800

1000

1200

1400

1600

1800

20

41

20

42

20

43

20

44

20

45

20

46

20

47

20

48

20

49

20

50

20

51

20

52

20

53

20

54

20

55

20

56

20

57

20

58

20

59

20

60

Year

Va

lue

(m

m)

PrecipitationETWater Yield

GHG Scenario

Monthly water balance components for Ganga river basin

0

50

100

150

200

250

300

350

Ja

n

Fe

b

Ma

r

Ap

r

Ma

y

Ju

n

Ju

l

Au

g

Se

p

Oct

No

v

De

c

Year

Valu

e (

mm

)

PrecipitationETWater Yield

Control

Scenario

0

50

100

150

200

250

300

350

Ja

n

Fe

b

Ma

r

Ap

r

Ma

y

Ju

n

Jul

Au

g

Se

p

Oct

Nov

De

c

Year

Valu

e (

mm

)

PrecipitationETWater Yield

GHG

Change in Monthly water balance components for Ganga river basin

-30

-20

-10

0

10

20

30

40

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Year

Va

lue

(m

m)

PrecipitationETWater Yield

Change in monthly water balance for

Control and GHG climate scenarios

-40

-20

0

20

40

60

80

100

120

140

160

180

Ja

n

Fe

b

Ma

r

Ap

r

Ma

y

Ju

n

Ju

l

Au

g

Se

p

Oct

No

v

De

c

Year

Va

lue

(%

)

PrecipitationETWater Yield

Change (%) in monthly water balance

for Control and GHG climate scenarios

Sub-basin Water Balance components for Ganga Basin

0

1000

2000

3000

4000

5000

6000

7000

1 2 3 4 5 6 7 8 9 10 11 12 1314 15 16 17 18 192021 22 23 24 25 2627 28 29

Subbasin

Va

lue

s (

mm

)

PrecipitationETWater Yield

Control Scenario

0

1000

2000

3000

4000

5000

6000

7000

1 2 3 4 5 6 7 8 9 101112 1314 15 1617 181920 2122 23 2425 262728 29

Subbasin

Va

lue

s (

mm

)

PrecipitationETWater Yield

GHG Scenario

Ganga River – Annual Peak

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

ail

y p

eak d

isch

arg

e

(cu

mecs)

Control ScenarioSubbasin 11

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily p

ea

k d

isch

arg

e

(cu

mecs)

GHG ScenarioSubbasin 11

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily

peak d

isch

arg

e

(cu

mecs)

Control ScenarioSubbasin 23

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily

peak d

isch

arg

e

(cu

mecs)

GHG ScenarioSubbasin 23

Events exceeding arbitrary thresholds in Ganga River Basin

Discharge (cumecs)

Control GHG Control GHG

Ganga Subbasins Sub11 Sub11 Sub23 Sub23

Discharge>10000

>20000

6 7

1 5

Discharge>12000

>30000

1 6

0 2

Flow Duration Curve for Ganga River for Control and GHG scenarios

0.00001

0.0001

0.001

0.01

0.1

1

10

100

1000

10000

100000

0 10 20 30 40 50 60 70 80 90 100

% of time flow equal or exceededF

low

(C

um

ec

s)

ControlGHG

Ganga River - Flow Duration Curve

Dependa

ble Flow

(cumecs)

25% 50% 75% 90%

Control 4648 716 12.88 0.4394

GHG

Scenario

3649 754.5 50.5 5.323

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

Thank you