climate variability, urbanization and water in...
TRANSCRIPT
Climate Variability, Urbanization and Water in India
M. Dinesh Kumar
Executive Director
Institute for Resource Analysis and Policy
Hyderabad-82
Email: [email protected]/[email protected]
Prepared for the Orientation Workshop organized by SaciWaters
Purpose
• The purpose of this presentation is to add a new dimension to the debate on how climate change and urbanization could impact on India’s water resources vis-à-vis its availability and demand, in the face of the country’s climate reality
Plan of Presentation
• Conceptual Framework on the Impacts of Climate Variability and Change and Urbanization on Water
• India’s Climate Reality
• India’s Urban Growth Reality
• Issues with climate predictions
• Potential Impacts of Climate Change on Water Resources
• Potential Impacts of Urbanization on Water Resources
• Areas of Future Concern
Conceptual Framework
• Farming is the largest consumptive user of water in India
• Change in temperature and CO2 can alter crop yields by affecting plant bio-physical processes: depends on plant type (C3 or C4)
• Temperature change can also alter evapo-transpirative demand of water (ET) in crop production
• Either way, the amount of water required for producing a unit of biomass would change, changing the aggregate water demand in agriculture
• Temperature changes can alter the hydrological system, by changing infiltration rate, soil moisture storage, and thereby run-off, affecting the overall water availability within a basin
Conceptual Framework
• Urbanization can affect hydrology and water resources in many ways
• Urban centres create points of concentrated water demands, often making it difficult for the local natural water systems to sustain
• Urbanization pushes the growth rate in domestic water demands as per capita water demands are much higher in urban areas
• Urbanization changes land use, creating impervious catchments and increasing the runoff from precipitation, thereby increasing the chances of floods, while reducing natural recharge to groundwater
• Urbanization increases the level of toxic pollutants and sediment load in storm water runoff, making it unfit for human & animal consumption
India’s climate reality
• Spatial variability in climate is very significant:
– Hot & arid to hot & humid, to cold & sub-humid to cold & humid
• Within the same river basin, agro climate vary significantly
• Day time and night time temperature of a day can vary from year to year; so are humidity and wind speed
• Monsoon records for 104 years (1901-2003) do not show any linear trend (Kelkar, 2010)
• Also data for 1813-2006 do not show any uniform trend (Sontakke et al., 2008)
India’s climate reality
• Spatial variation in rainfall is remarkable
• So is the variation in number of rainy days
• Regions of low rainfall receive it in very few showers; regions of high rainfall have long wet spells
• Regions of high mean annual rainfall has low inter-annual variability and vice versa
• Regions experiencing fewer days of rains experience high variability in number of rainy days between years
India’s urban growth reality
• Urban population growth in India is much higher than that of rural population growth ; large cities are growing faster
• Cities in ‘naturally water scarce regions ‘ are experiencing faster growth than those in water abundant regions
• Water demands in these cities are growing exponentially; while their local fresh water bodies are either drying up or getting deteriorated;-tanks and lakes and hard rock aquifers in South India
• These urban areas are increasingly dependent on water resources in rural areas, often competing for water from public irrigation systems
Issues with climate prediction for India
• GCMs predict higher rainfall for Indian sub-continent, with varying “increments”; not robust for Indian monsoon (Kelkar, 2010)
• The observed trends in “global temp. rise” are not uniform. Greater warming is predicted for n. hemisphere
• GCM predictions are too broad (150 km X 150 km area.), and do not have much relevance for understanding river basin hydrology
• Different models predict different trends (Mujumdar, 2010). Often, errors in rainfall predictions are higher than the predicted values
• Generally, temperature predictions are found to be more accurate than the rainfall predictions at the global scale
Climate change impacts on water resources
• Even if climate change is a reality, its impacts on water resources in India would not be uniform across basins and regions; but would depend on the region
• In low to medium rainfall regions, rise in temperature could lead to faster soil moisture depletion and reduced runoff and recharge
• In low to medium rainfall semi arid regions, basins are water-scarce
• Temp. rise could also lead to further increase in the demand for water for crop production, thereby increasing magnitude of water scarcity
• The impacts of droughts due to monsoon failure in these regions would become more severe
Climate change impacts on water resources
• In high rainfall, (above 1,000mm), hot & sub-humid to cold & humid regions), an overall rise in temperature rise could lead to higher rainfall increasing surface water availability
• Water demand for crop production is quite low in these regions.
• A rise in temp. won’t cause much increase in irrigation water demand, as more water would be available from soil moisture for crop growth
• Further, the basins in these regions are water-abundant basins (Ganges, Brahmaputra-Meghna), with limited amount of arable land for crop production
Climate change impacts on water resources
• On the contrary, temperature reduction can cause opposite trends in
these two distinctly different hydro-climatic regimes.
• The naturally water-scarce regions could receive more rainfall, and that in naturally water rich regions could decline
• Accumulation of particle aerosol in the atmosphere over the Gangetic plains is reported to be leading to lower temperature, and reduction in rainfall in that region and also crop yield losses owing to decline in incident solar radiation
Impact of climate variability and urbanization on water resources
• Low to medium rainfall regions in India experience high variability in stream flows and groundwater recharge
• The variability might increase if the temperature in these regions experience rise
• Fast growing urban centres in naturally water-scarce regions induce huge pressure on the limited freshwater, with excessive increase in water demands, depleting local aquifers and highly variable flows
• With climate change, the occurrence of climate induced water-related disasters like droughts and urban floods are likely to be more i
Areas of concern for future
• Water scarcity are growing in India, and challenges of managing water would be greater in years to come
• There are issues associated with climate predictions for India, particularly rainfall. But, even under the best case scenario, there could be some human induced climate impacts, which are negative
• But, there are priority issues in water management, which need to be addressed
• Generating accurate scientific data on climate and hydrology is one among them (temp., rainfall & its intensity, stream flows, base flows, groundwater recharge & withdrawal, glaciers etc.)
Areas of concern for future
• Addressing these fundamental issues would help plan for climate induced impacts
• More importantly, India has capabilities to adapt to the changes which the current predictions on climate shows
• Further strengthening these capabilities would require :
– Management of aquifers in the water-scarce regions
– Building multi-annual storage in reservoirs
– Improving water productivity in irrigated agriculture would be key to strengthening our adaptive capacities and reducing emissions
Rainfall and ET0 in Nine agro climatic sub-zones in Narmada basin
0
200
400
600
800
1000
1200
1400
1600
1800
2000
CNV - Jabalpur CNV - Hosangabad
Kymore Plateau & Satpura Hills
Malwal Plateau Nimar Plains Northern Hill Region of
Chhattisgarh
Satpura Plateau Satpura Plateau Vindhya Plateau
mill
imet
res
Annual ET0 (mm) Average Normal Rainfall (mm)
Variations in daily min. and max. temperature between years
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
1
12
23
34
45
56
67
78
89
10
0
11
1
12
2
13
3
14
4
15
5
16
6
17
7
18
8
19
9
21
0
22
1
23
2
24
3
25
4
26
5
27
6
28
7
29
8
30
9
32
0
33
1
34
2
35
3
36
4
Tem
pe
ratu
re in
de
gre
es
C
Temperature of Aurangabad (2009 and 2010)
Daily Max Temp-2009 Daily Max Temp-2010
Daily Min Temp-2009 Daily Min Temp-2010
Relative humidity and wind speed
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
0
10
20
30
40
50
60
70
80
90
100
1 10
19
28
37
46
55
64
73
82
91
10
0
10
9
11
8
12
7
13
6
14
5
15
4
16
3
17
2
18
1
19
0
19
9
20
8
21
7
22
6
23
5
24
4
25
3
26
2
27
1
28
0
28
9
29
8
30
7
31
6
32
5
33
4
34
3
35
2
36
1
Win
d S
pe
ed
KM
PH
Re
lati
ve H
um
idit
y %
RH%-AM-2009 RH%-AM-2010 RH%-PM-2009
RH%-PM-2010 Wind Speed (KMPH) - 2009 Wind Speed (KMPH)-2010
Rainfall variability across regions
Variability in rainy days
Rainfall variability between years
Variability in rainy days between years
City Size Vs Surface water Contribution to Water Supply
Water-scarce basins & regions
Sr. No Name of the Basin
Mean Annual Rainfall (mm)
Average Annual Water Resources1mm)
Effective Annual Water Resource2 (mm)
Reference Evapo-transpiration3
(mm)
Upper Lower Upper Catchment
Lower Catchment
1 Narmada basin 1352.00 792.00 444.70 937.60 1639.00 2127.00
2 Sabarmati basin 643.00 821.00 222.84 309.61 1263.00 1788.80
3 Cauvery basin 3283.00 1337.00 316.15 682.80 1586.90 1852.90
4 Pennar basin 900.00 567.00 193.90 467.80 1783.00 1888.00
5 Krishna basin 2100.00 1029.00 249.16 489.15 1637.00 1785.90
Average Reference Evapo-transpiration Against Effective Annual Water Resources in Selected River Basins in Water-Scarce Regions
Water-abundant basins & regions
Name of the basin
Average Annual Rainfall in the basin (mm)
Average Renewable Water Resources (m3/capita/ annum)
Average Effective Water Resources (m3/capita/ annum)
Mean Annual Reference Evapo-transpiration (mm)
Water Demand for Agriculture (m3/capita/ annum) Upper Lower Upper
Catchment Lower Catchment
Ganga 1675.0 1449.0 1179.9 1399.4 710.0 1397.0 721.5
Brahmaputra 2359.0 2641.0 1737.1 2052.8 1064.0 1205.0 1180.9
Annual Yield of three Sub-basins of Sabarmati River Basin
0
1000
2000
3000
4000
5000
6000
19
50
19
53
19
56
19
59
19
62
19
65
19
68
19
71
19
74
19
77
19
80
19
83
19
86
19
89
Yie
ld in
Mil
lio
n C
ub
ic M
etr
es
Total Yield from Dharoi
Total Yield from Watrak
Total Yield from Hathmati
Historical Inflow series for Narmada River at Sardar Sarovar Dam Site, CWC (1891-1990)