Climate Change and its

Impact on Water

Resources of India

Sandhya Rao

INRM Consultants, New Delhi

Climate Change - Concerns a warmer Earth may lead to changes in rainfall

patterns

Impacts range from Water

• Floods

• Droughts

• Glacier melt

• Sea level rise

Agriculture • Crop shift - regional

• pests

Forest • Species shift

• Forest fires

Human Health • Temperature related

• malaria

Infrastructure

Issues in Climate Change Evidence

Eleven of the last twelve years rank among the 12 warmest years on record (since 1850), with the warmest two years being 1998 and 2005

Science of Climate Change Models

• Global climate models can predict future climate on scales of 300 km or more

• Regional climate models, driven by output from the global models, provide information on scales of 25 km or 50 km over limited geographical regions, suitable for national climate impact assessments and planning adaptation

IPCC Special Report on Emissions Scenarios • cover a broad range of assumptions about future economic and

technological development, including some that allow greenhouse gas emission reductions

Impact Sectors, levels (food production, ecosystems)

Vulnerability regions, sectors

Adaptation costs, obstacles, options

Mitigation options, costs, barriers

IPCC 4th Assessment Report

(2007) Impacts in Asia Potential impacts of climate change are likely to be

substantial without further adaptation: current water security problems are likely to increase by 2050

Substantial impacts on agriculture and forestry are very likely by 2050

Increase in coastal water temperatures would exacerbate the abundance and / or toxicity of cholera in South Asia

The structure, function and species composition of many natural ecosystems are very likely to alter

Risks to major infrastructure are likely to increase

The current trends of glacial melts suggest that the snow fed rivers like Ganga, Indus, Brahmaputra could likely become seasonal rivers in the near future and could likely affect the economies in the region

Impact on Water Resources

Impacts of climate change and climate variability on the water resources are likely to affect irrigated agriculture

installed power capacity

reduced water flows in the dry season - droughts

higher flows and resulting flood problems during the wet season

Water supply, urban storm

To drive a hydrological model reliable information on local and regional climatological variables (e.g. temperature, precipitation, evapotranspiration, etc.) and their distribution in space and time is required statistical downscaling

dynamical downscaling

PRECIS – Indian Simulation

Indian RCM PRECIS has been configured for a domain extending from about 1.5°N to 38°N and 56°E to 103°E

present (1961–1990) and a future period (2071–2100)

two different socio-economic scenarios characterized by regionally focused development with priority to economic issues in one (A2 scenario)

environmental issues in the other (B2 scenario)

simulations with and without including sulphur cycle, to understand the role of regional patterns of sulphate aerosols in climate change

Impact of Climate Change on

water resources - India Initial National Communication of India to

UNFCCC

For Ministry of Environment and Forests

To quantify the impact of the climate change on

the water resources of India, Identify Hotspots,

Identify Adaptation & Coping strategies

12 river basins modelled

Flood and drought analyses have been

performed

Tools Used

Modelling: SWAT (Soil and Water

Assessment Tool) model used - provides

opportunity for scenario generation

GIS framework: acts as a pre-processor

for the distributed modelling and is also a

powerful tool for visualization of the

outputs/results in terms of V & A

Data Used for Modeling

Digital Elevation Model: 1km grid, generated using 1:250,000 topographic map

Land use: Global data, 1:2M USGS

Soil: Global data, 1:5M FAO

Drainage: 1:250,000

Weather: Data generated in transient experiments by the “Hadley Centre for Climate Prediction” U.K. at a resolution of 0.44° X 0.44° latitude by longitude grid points obtained from IITM, Pune

River Basins Modeled

Layers

DEM

Delineated Basins

Landuse

Soil

Weather

Impact studied

Impact on annual water availability

Impact on seasonal water availability

Impact on inter annual water availability

Regional Variability of Water availability

Extreme events – Floods and Droughts

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

40M

ah

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

Trend in Precipitation, Runoff and

Evapotranspiration for Control and GHG

Climate Scenarios

Control GHG

Control GHG

Control GHG

Increase in precipitation in Mahanadi, Brahmani, Ganga, Godavari, and Cauvery, for the GHG scenario the corresponding total runoff for all these basins

has not necessarily increased

Cauvery and Ganga show decrease in total runoff. This may be due to increase in evapotranspiration on account of increased temperatures or variation in the distribution of the rainfall

In the remaining basins decrease in precipitation has been expected The resultant total runoff has decreased in majority

of the cases but for Narmada and Tapi

Key Findings Under the GHG scenario the

conditions may deteriorate in terms of severity of droughts in some parts of the country and enhanced intensity of floods in other parts

there is a general overall reduction in the quantity of the available runoff under the GHG scenario

Luni with the west flowing rivers Kutch & Saurastra which occupies about one fourths of the area of Gujarat and 60 percent of the area of Rajasthan shall have acute physical water scarce conditions

River basins of Mahi, Pennar, Sabarmati, Krishna and Tapi shall face constant water scarcities and the water shortage conditions

River basins belonging to Cauvery, Ganga, and Narmada shall experience seasonal or regular water stressed conditions

River basins belonging to Godavari, Brahmani and Mahanadi shall have rare water shortages and if exist are only confined to few locations

Vulnerability Assessment –

Drought & Flood Soil Moisture Index to monitor drought severity

focuses on the agricultural drought where severity implies cumulative water deficiency

weekly information has been derived using daily SWAT outputs to incorporate the spatial variability

Daily outflow discharge taken from the SWAT output Maximum daily peak discharge has been identified for

each year and for each sub-basin

analysis performed to identify those basins where flooding conditions may deteriorate in the GHG scenario

Drought Analysis Godavari Subbasins with maximum

Monsoon & Non monsoon events in Control & GHG Scenario

Subbasin 23- Control

0

10

20

30

40

50

60

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

Weeks

Drought Weeks

Subbasin 27- Control

Maximum M drought w eeks

0

10

20

30

40

50

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

Weeks

Drought Weeks

Subbasin 27- GHG

0

10

20

30

40

50

60

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

Weeks

Drought Weeks

Subbasin 23- GHG

Maximum M drought w eeks

0

10

20

30

40

50

60

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

Weeks

Drought Weeks

Subbasin 14 - Control

Maximum NM drought w eeks

0

10

20

30

40

50

60

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

Weeks

Drought Weeks

Subbasin 14- GHG

0

10

20

30

40

50

60

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

Weeks

Drought Weeks

Subbasin 25- Control

0

10

20

30

40

50

60

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

Weeks

Drought Weeks

Subbasin 25- GHG

Maximum NM drought w eeks

0

10

20

30

40

50

60

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

Weeks

Series1

Maximum Monsoon Drought in Control Maximum Monsoon Drought in GHG

Maximum Non Monsoon Drought in Control Maximum Non Monsoon Drought in GHG

Spatial and temporal distribution of

drought conditions in Godavari Basin graduated colour depicts

spatial variability of

concurrent severity of

drought, number of sub-

basins where severe

concurrent conditions

prevailed in that year

size of the blue dot reveals

the number of drought weeks

experienced in each sub-

basin over the 20 years

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Subbasins

To

tal

Dro

ug

ht

Even

ts (

Weeks) Total Drought Event (control)

Total Drought Event (GHG)

®0 40,00080,000120,000160,00020,000

Km

Godavari Present Scenario

Total Drought Weeks

9 - 14

15 - 18

19 - 21

22 - 27

28 - 32

Godavari Present Scenario

Concurrent Drought Years

1981 (12)

1982 (6)

1983 (6)

1984 (2)

1985 - 1986 (1)

Flood Analysis

Annual

maximum daily

peak discharges

for two sub-

basins of

Godavari river

basins for

Control and

GHG scenarios

0

10000

20000

30000

40000

50000

60000

70000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily p

eak d

isch

arg

e

(cu

mecs)

Control ScenarioSubbasin 25

0

10000

20000

30000

40000

50000

60000

70000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily p

eak d

isch

arg

e

(cu

mecs)

GHG ScenarioSubbasin 25

0

5000

10000

15000

20000

25000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily p

eak d

isch

arg

e

(cu

mecs)

Control ScenarioSubbasin 21

0

5000

10000

15000

20000

25000

1 3 5 7 9 11 13 15 17 19

Year Number

An

nu

al d

aily p

eak d

isch

arg

e

(cu

mecs)

GHG ScenarioSubbasin 21

Uncertainties

Uncertainties in Climate Simulation

Assumptions and Coarseness of the Data

Landuse has been coarse

detailed data on the agricultural land use and

the cropping pattern has not been used

Soil type and profile has also been scanty

Water bodies including reservoirs were not

incorporated due to lack of data on their

capacities and the operation rules

Adaptation Issues

Strategy for coping can be no different from the present day strategy of coping with the ever increasing demands and other environmental impacts Prerequisite is the application of Integrated Water Resources

Management strategy at different levels of usage starting from individual households to local communities, watersheds to catchments

Some of the current strategy which need to be strengthened Command Area Development programme

Crop Diversification, Irrigation Water Management

Conjunctive use of Surface and Ground Water, Reuse of Waste Water

Flood Control and Flood Management , Inter-Basin Transfer of Water

There is no single “best” coping strategy to enhance the coping capabilities to climate variability and change choice is a function of many factors pertaining to economic efficiency,

risk reduction, robustness, resilience, reliability etc.

emerging technologies for short-term weather forecast for real-time water management and operations

Future Improvements

Use HaDRM3 simulation – daily

Incorporate man made interventions like

reservoirs, dams etc

Identify hotspots with respect to drought, floods,

incorporating socioeconomic and other desired

parameters

Pilot level flood zone mapping for river basin

Integration of the results from water sector with

other sectors to formulate coping strategies

Thank You