Modeling Impact of Climate Change on Hydrology of the Brahmani River Basin, India

Transcription

1 Modeling Impact of Climate Change on Hydrology of the Brahmani River Basin, India Alok Kumar Sikka National Rainfed Area Authority, Planning Commission, Government of India, New Delhi, India Adlul Islam ICAR Research Complex for Eastern Region, Patna, India

2 Background Climate change is one of the biggest issues confronting humanity It influences basin hydrology and regional water availability By the , models estimate increase in global mean surface temperature of about (IPCC 2007) ºC with the low emission scenario ºC with high emission scenario A warming of 0.4ºC noticed in surface temperature in India over , with no significant long term trend in monsoon rain Projections indicate that rainfall in India may increase by 15-40% with high regional variability More pronounced warming, northern India experiencing more increase, with relatively greater warming in winter & post-monsoon seasons.

3 Population and Water Resources India has 2% of world s land 4% of world s freshwater resources 16% of world s population 17% of world s cattle population Precipitation: Most of it confined to monsoon of just about 100 hr Makes irrigation imperative for reliable agricultural production Necessitates storage in various forms

4 Water Resources Vital Statistics Rainfall: 4000 bcm/yr. Annual utilizable surface and groundwater is 1122 bcm. Water consumers - Agriculture (85%); Domestic (4-5%) Availability of water (cu.m/ca/year) World: India : ~ 1700 Water storage (cu.m/ca/yr) World : 900 India : ~ 210 Growing water scarcity & food in security additionally threatened by climate change Projected Population (Million) Stress Condition Per capita availability Year Scarcity condition Population (million) Per caita water availability (m 3)

5 Brahmani Basin: a Case Study Distributed parametric modeling approach to reflect spatial heterogeneities- using USGS Model: Precipitation Runoff Modeling System (PRMS) Major inputs Daily precipitation Temperature (Min and max) Solar radiation (Optional) Terrain, soil & land use Major outputs Water balance components Runoff, ET, soil moisture Sub-surface & groundwater Sensitivity of streamflow to hypothetical climate change scenarios Off-line approach with projected climate change from Had CM3 and PRECIS generated climate change scenarios

6 PRMS Model Maximum Temperature Evapotranspiration Evaporation Minimum Temperature INTERCEPTION Precipitation Evaporation Evaporation Transpiration Transpiration SOIL ZONE RESERVOIR Recharge Zone Lower Zone IMPERVIOUS ZONE RESERVOIR Surface Runoff Surface Runoff Groundwater Recharge GROUNDWATER RESERVOIR SUBSURFACE RESERVOIR Groundwater Recharge Subsurface Flow Groundwater Flow Streamflow Groundwater Sink

7 Data Used for Modelling: Daily streamflow and rainfall data ( ) of four stream gauging stations (Tilga, Jaraikela, Gomlai and Jenapur) Daily rainfall and temperature data for 11 stations spread over the basin Toposheets of 1:250,000 scale and 60 m contour interval Soil and land use map from National Bureau of Soil Survey & Land Use Planning DEM layer developed with 30 m of spatial resolution

8 Brahmani Basin Total catchment area= 39,313 km 2 Orissa (57.3%), Jharkhand (39.2% Chhattisgarh (3.5%) Sub-basins: Tilga, Jaraikela, Gomlai Jenapur Tilga 2987 Km 2 Gomlai Km 2 Jaraikela Km 2 Sub-humid tropical climate Avg. annual rainfall 1305 mm Jenapur Km 2

9 Hydrological Response Units (HRUs) The DEM along with soil and land use layers are used for generation of spatially distributed hydrological response units 19 different HRUs classes have been generated Total number of HRU 66

10 Calibration & Validation: Jenapur Calibration Validation E R

11 Streamflow Sensitivity 4 C rise in temperature resulted in 11.4% decrease in annual streamflow, with maximum decrease (12%) during monsoon and minimum (2.7%) during pre-monsoon season. 10% decrease in rainfall resulted in 22.9% decrease in annual streamflow, with maximum decrease (25%) in monsoon followed by post-monsoon and pre-monsoon season

12 Combined Effect of Rainfall and Temperature Changes Temperature rise of 4 C and a 10% decrease in rainfall resulted in 32.90% decrease of annual streamflow, with maximum reduction (35 %) in monsoon and minimum in pre-monsoon. 4 C rise of temperature and 30% increase in rainfall resulted in 62.2 % increase in annual streamflow, with maximum increase (72.5 %) in monsoon and minimum in winter.

13 Change in Mean Monthly Streamflow Maximum absolute changes in streamflow during the month of July streamflow almost doubled with 30% increase in rainfall & minimum absolute change (32.90%) in the month of January. With 30% increase in rainfall and 4 C increase in temperature, the magnitude of changes in mean monthly streamflow ranged from 83.40% (July) to 26.90% (January). A maximum decrease of 37% (July) was simulated with 4 C increase in temperature together with 10% decrease in rainfall.

14 Effect of Climate Change: HadCM3 Scenarios Under A2a emission scenario 15, 9 and 26% increase in annual streamflow was estimated during 2020, 2050, and 2080 respectively. Under B2a emission scenario, 23 and 28% increase in annual streamflow estimated during 2050 and 2080

15 Monthly Changes with HadCM3 Scenarios Percentage increase in monthly streamflow is simulated to be maximum in May during 2020, 2050 and 2080 under A2a emission scenario. Decrease in flow during October and December 2020, June 2050, and June and February 2080 under A2a scenario. Decrease in flow during June and February 2020, February 2050, and October to December 2080 under B2a emission scenario.

16 Effect of Climate Change: PRECIS scenarios ( ) Increase in annual as well as seasonal stream flow 52.5% increase in annual streamflow Maximum increase (94%) premonsoon season Minimum increase (43%) monsoon season Variation in result under different emission scenarios and climate models

17 Conclusions Brahmani basin s stream flow is more sensitive to changes in rainfall than temperature. Increase in seasonal and annual streamflows with HadCM3 and PRECIS climate change scenarios under A2a and B2a emission. Decreased streamflow simulated during winter months (December- February) and June in most cases has implications for winter crops (Rabi) and meeting peak water demands during summer. While increased flow during monsoon could lead to more flooding and water logging. Suggests need for development/adoption of agronomic, land and water management related adaptation measures. Emerging policies and priorities may focus on water user/use specific interventions, integrated management of watersheds and basin, demand side management, promoting community based approaches, and bridging knowledge gaps for benefit of users.

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