91-The Lost River Saraswati-A Blessing for Drought Proofing in Arid Environment of Western Rajasthan, India.

Abstract

There is deep belief that discovery of palaeo-courses of vedic Saraswati can be a blessing for the Great Thar Desert in arid lands of western Rajasthan. Evidences in support of existence of palaeo-drainage include mythological, early literary writings, archaeological findings, remote sensing studies, geomorphic and other features, fluvial deposits, geophysical studies, occurrence of fresh groundwater pockets and isotope studies etc. The river was lost during prehistoric times due to neo-tectonic and aeolian activities causing river piracy and its disorganization. The river has recharged potential aquifers like Quaternary alluvium, Palane, Nagaur and Lathi Sandstones containing waters of 7000 to 9500 years old. However, occurrence of freshwater potential aquifers feasible for construction of thousands and lacs of tube wells is a misconception since the palaeo-channels are buried under a mantle of aeolian cover and presently having no connections with the Himalayan waters. Also, fresh groundwater resources in the palaeo-floodplains during earlier times might have turned in to saline/brackish belts/pockets owing to present day aridity. Demarcation of buried channels in field is a difficult but possible task and has gained paramount importance for implementing mega artificial recharge projects. Precise delineation of palaeo-channels needs to investigate in a long term project mode with integrated multidisciplinary approach incorporating science of hydrogeology, geophysics, geochemistry, sedimentology, mineralogy, paleontology and so on. Non-committed waters from northwest India especially those flowing to neighboring country during monsoon and efficient use of Indira Gandhi Nahar Pariyojana water may be source of surface water for recharge. Deep groundwater levels and permeable geo-formations make the scenario conducive for large scale artificial recharge to groundwater through palaeo-channels. About 71,000 MCM of water can be gradually artificially recharged, which may be retrieved at any point of time and space through wells and tube wells and thereby perennial availability of water irrespective of deficit rains i.e."Drought Proofing" of permanent nature in arid lands of western Rajasthan.