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