19.-Rainwater harvesting technology in Indian desert

Abstract

Water is scarce commodity in the 11 arid districts of Rajasthan covering 1,96,150 km2 area. Low and erratic rainfall, dominantly deep dry sandy soil terrain with dune bodies, total absence or disorganised natural drainage in major part, very deep and saline ground waters, very high evaporative conditions and frequent dust storms events makes the region most inhospitable for all in general and human in particular. Spatially, eastern margin of the desert receives more annual rainfall (500 mm) than the western international boundary (100 mm). Along with this decreasing rainfall gradient westward, there is increasing gradient of variability in rainfall as also evaporation. Thus, coefficient of variability in rainfall is 40 per cent in the east which increases to 70 per cent in western part of Jaisalmer district, while the annual evaporation is less than 1000 mm in east and it exceeds gradually 2000 mm in west. However, the rainy season is confined to a period June to September, when 90-95 per cent of the total annual rainfall is received. Within this broad setting, there is again local spatial variability in rainfall events, even in the small areas. Under such conditions, considering the general water requirement, the availability of water resources is highly uncertain. In this backdrop of uncertainties that the rainwater management using is found to be valuable. There are some hilly, rocky, stony and gravelly surfaces interspersed in this region, that generate good runoff which may be harvested and utilized for conjunctive use. Rainwater management has, therefore, to be looked into in the context of maximising water availability in the face of increasing demand for domestic consumptive and for biomass production on sustainable basis.