Crop Water Demand under Climate Change Scenarios for Western Rajasthan

Abstract

Climate change due to greenhouse effect is expected to cause major changes in natural eco-system of some of the areas. The change in climate is likely to profoundly influence hydrological cycle viz. precipitation, evapotranspiration, soil moisture, etc. Evapotranspiration (ET) being the major component of hydrological cycle will affect crop water requirement and future availability of water resources. The most visible signature of climate change is rise in temperature by few degrees varying over different regions. Temperature being principle source of energy, will have major effect on ET and consequently on water demand. The study has been conducted for hot arid zone of western Rajasthan. Penman-Monteith model was used for the estimation and sensitization of ET. Study suggests that as small as 1°C rise in temperature from normal will enhance the annual ET demand from minimum of 35 mm for Ganganagar district to maximum of 96 mm for Jaisalmer district. Enhanced ET would primarily be a consequence of higher air and land surface temperature. The increase in ET demand will have a direct bearing on total water demand for irrigation. The rise in temperature by 1°C will cause an additional annual water demand of 1570.9 Mm3 for the entire western Rajasthan based on net irrigated area of 31,64,512 ha. The total available utilizable ground water for western Rajasthan is 3516.9 Mm3 and rise of 1°C in normal temperature will put additional stress of 44% on existing groundwater resources based on present land use pattern. An attempt has been made in the present study to estimate the water demand under climate change scenario for the hot arid zone of western Rajasthan. Key words: Evapotranspiration, water resources, global warming, climate change.