ISOTOPE STUDY OF GROUNDWATER IN ARID AREAS OF JAISALMER

In order to understand the ground water recharge process in Shahgarh a rea of arid Jaisalmer district, an environmental isotopic study based on measurement of D, O-18 and H-3 contents was carried out on shallow groundwaters. The area is characterized by very low rainfall. sandy te rrain and very little vegetation. Water level in the scattered shallow wells and hand pumps varies from 10 to 30 m. Stable isotope analysis of the water samples indicate very high depletion of the heavy isotope contents, i.e., delta D(similar to)50 parts per thousand and delta O- 18-6 to -7 parts per thousand, and suggest quite old origin of these w aters. The H-3 contents are also very low. A H-3 tracer injection expe riment at Mehrana indicated negligible recharge due to modern precipit ation. The ground water is potable to brackish, the TD3 ranging from 2 00 to 1500 mg/l. A higher fluoride content was observed in two wells.