11-Groundwater Scenario under Changing Climate - Rajasthan.

Abstract

One of the primary threats from climatic changes is because of increase in evaporative losses and water demands caused by higher temperature. The increase in water demand due to increase in evaporative losses will have direct bearing on water resources. Ground water is the major source of irrigation. Change in crop water requirement due to increased evapotranspiration is likely to affect groundwater resources of any region. This paper analyzes likely effects of climate change on evapotranspiration demand (or crop water requirement) and consequently on the groundwater resources of Rajasthan state. FAO Penman-Monteith model (1998) was used to estimate evapotranspiration (ET). The average annual ET demand for the State of Rajasthan is estimated as 1701 mm. One percent increase in temperature (or 5 0.42°C) over the prevailing temperature would enhance the annual evapotranspiration demand by 11.7 mm, which indicated requirement of additional annual water demand of 718 mcm for the net irrigated area of 61,345 km2 and 2,245 mcm for the total cropped area of 1,92,302 km2 in the State. In comparison to the total available utilizable ground water of 11,159 mcm in Rajasthan, these additional requirements would put stress of 6.43% to 22.16% with land use pattern remaining unaffected. Increase in temperature by 1% will reduce number of safe districts from 6 to 3 and bring additional districts in the category of 'critical' and 'overexploited'. An increase in temperature by 2-3% over normal temperature (i.e. 0.82-1.24°C) will reduce the category of 'safe' zone district into 1, remaining 31 districts will be mostly in the category of 'overexploited'. The paper also discusses groundwater resource scenario of Rajasthan and its probable effect due to climate change.