CS/AR/2005-06: Artificial Recharge Studies: Identification of Potential Underground Reservoir in Tirupati Sandstone Formations

Abstract

Variation in groundwater level has been analyzed to understand the process of groundwater recharge and its flow in upland Tirupati Sandstone Aquifer. The Deuterium and Oxygen-18 isotopes are used to understand the contribution of different recharge sources and also the most important groundwater recharge source for the study area. The present paper describes the ground water condition in the region and gives detailed account of stable isotope characteristics of the aquifer. The analysis presented the variation of local meteoric precipitation line with respect to groundwater line as δD vs. δ18O plots for 2004 and 2005. In this study a relationship is established to understand the characteristics of groundwater recharge in an upland sandstone aquifer with respect to rainfall. Studies and analysis of data for 15 villages illustrates that the ground water table has fallen to depths of about 30 to 50 meters below ground level in the area, which has about 2200 electric motors with an average installed capacity of 10HP capacity. It indicates that the area is underlain by a huge underground reservoir from which about 120 MCM of groundwater is withdrawn annually and need to be recharged artificially for the survival and development of those who depend on the success of this infrastructure. Also, it is observed that the δ18O values of the groundwater of the aquifer are changing from pre monsoon to post monsoon even at large depth indicating the porous nature of the aquifer and the presence of rainfall recharge in the aquifer. The results on spatial variation of the δ18O values in the study are useful in identifying suitable locations for undertaking artificial recharge measures in the aquifer to supplement the natural recharge to groundwater aquifer. The suitability of upland aquifers for undertaking groundwater recharge is discussed for a sand stone aquifer from observed piezometer data. The study of rainfall recharge in the study area during the wet rainy season of September and October 2005 indicated that on the average a daily rainfall of 17mm can yield in a rise of about 29 cm of groundwater level in the aquifer. This is a positive signature of the aquifer to take up appropriate natural or artificial water conservation measures. Such application undertaken at other upland areas may help in evolving suitable relationship of rainfall and recharge