Climate Change Impact Assessment on Indian Water Resources

Ashvin Gosain, Sandhya Rao, Debajit Basu Ray

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• DEM: 1km grid, generated using contours

from 1:250000 topographic data

• Land use: 1:2M USGS

• Soil: 1:5M FAO

• 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

Assumptions

• The land use has been assumed to remain same

• Water bodies including reservoirs could not be incorporated at this stage due to lack of data - capacities and the operation rules

Drought Prone Basin-Krishna River Basin Annual water balance components

Krishna

0

200

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1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

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1996

1997

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2000

Year

Val

ue

(mm

)

PrecipitationETWater Yield

Control Scenario

0

200

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1000

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2041

2042

2043

2044

2045

2046

2047

2048

2049

2050

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2052

2053

2054

2055

2056

2057

2058

2059

2060

Year

Val

ue

(mm

)

PrecipitationETWater Yield

GHG Scenario

Monthly water balance components for Krishna river basin

0

50

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250

300

Jan

Feb Mar

Apr

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Jul

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Sep Oct

Nov

Dec

Year

Val

ue

(mm

)

PrecipitationETWater Yield

GHG Scenario

0

50

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250

300

Jan

Feb Mar

Apr

May Jun

Jul

Aug

Sep Oct

Nov

Dec

Year

Val

ue

(mm

)

PrecipitationETWater Yield

Control Scenario

Change in Monthly water balance components for Krishna river basin

-100

-50

0

50

100

150

Jan

Feb Mar

Apr

May Jun

Jul

Aug

Sep Oct

Nov

Dec

YearV

alu

e (m

m)

PrecipitationETWater Yield

Change (%) in monthly water balance for Control and GHG climate scenarios

-50

-40

-30

-20

-10

0

10

20

30

Jan

Feb Mar

Apr

May

Jun

Jul

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Sep Oct

Nov

Dec

Year

Val

ue

(mm

)

PrecipitationETWater Yield

Change in monthly water balance for Control and GHG climate

Sub-basin Water Balance components for Krishna Basin

0

200

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600

800

1000

1200

1400

1600

1800

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Subbasin

Val

ues

(m

m)

PrecipitationETWater Yield

Current Scenario

0

200

400

600

800

1000

1200

1400

1600

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Subbasin

Val

ues

(m

m)

PrecipitationETWater Yield

GHG Scenario

Change in Sub-basin Water Balance components for Krishna

-350

-300

-250

-200

-150

-100

-50

0

50

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Subbasin

Val

ues

(m

m)

Change in PrecipitationChange in ETChange in Water Yield

Change in Water Balance Components

-70

-60

-50

-40

-30

-20

-10

0

10

20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Subbasin%

Ch

ang

e

% Change in Precipitation% Change in ET% Change in Water Yield

% Change in Water Balance Components

Current to GHG - Krishna Sub-basins

• Reduction in precipitation by about 20% of the current value

• Corresponding decrease in water yield over the sub-basins is varying between 30% to 50%

• Actual evapotranspiration reduced by about 5% over most of the sub-basins

Vulnerability Assessment Procedure

• Palmer Drought Severity Index (PDSI) widely used index– incorporates information on rainfall, land-use, and soil

properties in a lumped manner

• PDSI value– below 0.0 indicates the beginning of drought situation– A value below -3.0 as sever drought condition

• Soil Moisture Index to monitor drought severity – Narasiman, B., and Srinivasan, R., 2002

Number of drought weeks in Sub-basins of Krishna for Current to GHG scenarios

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Subbasins

To

tal

Dro

ug

ht

Eve

nts

(W

eeks

) Total Drought Event (current)Total Drought Event (GHG)

Krishna Sub-basins with maximum Monsoon & Non monsoon events

Subbasin 15- ControlMaximum M drought weeks

0

10

20

30

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50

60

0 2 4 6 8 10 12 14 16 18 20Year

Wee

ks

Drought Weeks

Subbasin 15- GHG

0

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50

60

0 2 4 6 8 10 12 14 16 18 20Year

Wee

ks

Drought Weeks

Subbasin 4 - ControlMaximum NM drought weeks

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20Year

Wee

ks

Drought Weeks

Subbasin 4- GHG

0

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50

60

0 2 4 6 8 10 12 14 16 18 20Year

Wee

ks

Drought Weeks

Subbasin 11- Control

0

10

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50

60

0 2 4 6 8 10 12 14 16 18 20Year

Wee

ks

Drought Weeks

Subbasin 11- GHGMaximum M drought weeks

0

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50

60

0 2 4 6 8 10 12 14 16 18 20Year

Wee

ks

Drought Weeks

Subbasin 13- Control

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50

60

0 2 4 6 8 10 12 14 16 18 20Year

Wee

ksDrought Weeks

Subbasin 13- GHGMaximum NM drought weeks

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16 18 20Year

Wee

ks

Drought Weeks

Krishna River - Flow Duration Curve

0.000010.0001

0.0010.010.1

1

10100

1000

10000100000

0 1 0 20 3 0 40 50 60 7 0 80 9 0 100

% of time Q equal or exceeded

Flo

w (

Cu

mec

s)

PRESNTFUTURE

0.034220.2969664.84261FUTURE

0.052510.578410464867PRESENT

90%75%50%25%Dependable Flow (cumecs)

Flood Prone Basin - Mahanadi River Basin Annual water balance components

Mahanadi

0

200

400

600

800

1000

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1400

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2000

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

Year

Val

ue

(mm

)

PrecipitationETWater Yield

Control Scenario

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2041

2042

2043

2044

2045

2046

2047

2048

2049

2050

2051

2052

2053

2054

2055

2056

2057

2058

2059

2060

Year

Val

ue

(mm

)

PrecipitationETWater Yield

GHG Scenario

Monthly water balance components for Mahanadi river basin

0

50

100

150

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250

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350

400

450

500

Jan

Feb Mar

Apr

May Jun

Jul

Aug

Sep Oct

Nov

Dec

Year

Val

ue

(mm

)

PrecipitationETWater Yield

Control Scenario

0

50

100

150

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350

400

450

500

Jan

Feb Mar

Apr

May Jun

Jul

Aug

Sep Oct

Nov

Dec

YearV

alu

e (m

m)

PrecipitationETWater Yield

GHG Scenario

Change in Monthly water balance components for Mahanadi river basin

-50

0

50

100

150

200

Jan

Feb Mar

Apr

May Jun

Jul

Aug

Sep Oct

Nov

Dec

Year

Val

ue

(mm

)

PrecipitationETWater Yield

Change (%) in monthly water balance for Control and GHG climate scenarios

-60

-40

-20

0

20

40

60

80

100

120

140

Jan

Fe

b

Ma

r

Ap

r

Ma

y

Jun

Jul

Au

g

Se

p

Oct

No

v

De

c

Year

Val

ue

(mm

)

PrecipitationETWater Yield

Change in monthly water balance for Control and GHG climate scenarios

Sub-basin Water Balance components for Mahanadi River Basin

0

500

1000

1500

2000

2500

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Subbasin

Val

ues

(m

m)

PrecipitationETWater Yield

GHG Scenario

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Subbasin

Val

ues

(m

m)

PrecipitationETWater Yield

Current Scenario

• an increase in precipitation, water yield and evapotranspiration has been predicted in all the sub-basins of Mahanadi

Flood Analysis - Mahanadi Basin

0

5000

10000

15000

20000

25000

30000

35000

40000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily

pea

k d

isch

arg

e (c

um

ecs)

Current ScenarioSubbasin 15

0

5000

10000

15000

20000

25000

30000

35000

40000

1 3 5 7 9 11 13 15 17 19

Year NumberA

nn

ual

dai

ly p

eak

dis

char

ge

(cu

mec

s)

GHG ScenarioSubbasin 15

0

10000

20000

30000

40000

50000

60000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily

pea

k d

isch

arg

e (c

um

ecs)

Control ScenarioSubbasin 21

0

10000

20000

30000

40000

50000

60000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily

pea

k d

isch

arg

e (c

um

ecs)

GHG ScenarioSubbasin 21

Events exceeding arbitrary thresholds in Mahanadi River Basin

7100Discharge>30000

13942Discharge>20000

Sub21Sub21Sub15Sub15Mahanadi Subbasins

GHGControlGHGControlDischarge (cumecs)

Flow Duration Curve for Mahanadi River for Control and GHG scenarios

• The flow for all the dependable levels has increased for the GHG scenario over the corresponding Current flow magnitude

• For the 50% level of dependability, the flow has marginally reduced

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

ecs

)

ControlGHG

3.18243.3911686103FUTURE

1.46815.912064716PRESENT

90%75%50%25%Dependable Flow (cumecs)

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

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1400

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1800

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

Val

ue

(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

40M

ahan

adi

Bra

hm

ani

Gan

ga

Go

dav

ari

Cau

very

Nar

mad

a

Tap

i

Kri

shn

a

Pen

nar

Mah

i

Lu

ni

Sab

arm

ati

River Basins

Cha

nge

from

Cur

rent

to G

HG

Sce

nari

o (%

)

Rainfall Runoff ET

Conclusions

• The study is the first step towards getting the realistic estimates of the possible climate change impacts across the country

• It has provided a framework to be used for integrated river basin planning and management which was missing so far

• There is lot of improvement that is desirable and is under process

Thank you