31.-Study of percolation ponds for artificial recharge - Development of chloride mass balance method

Abstract

The hard rock aquifers of southern and western India, receive less than 10% precipitation as natural recharge, and are witnessing over-exploitation. Consequently measures are being adopted to augment groundwater resources artificially. Percolation ponds (tanks), the most popular artificial recharge structures in India, are constructed across monsoon streams for the above purpose. However no detailed study was carried out to evaluate their performance quantitatively in different hydrogeological environs. This paper reports the development and testing of chloride mass balance method to determine the efficacy of percolation ponds situated in different geological terrains. Depending on the location of the percolation tank, varied percolation fractions (of impounded water) were obtained; Basalts: 0.20-0.30; Granite-gneisses: 0.30-0.45; and Sandstones: 0.60, thus conforming to the transmission properties of rocks. In addition to geologic and climatic controls, the study also demonstrates enhancement of percolation ( capture recharge) as a result of higher abstraction of groundwater in the downstream area of the tank. Thus the study demonstrates the potential use of chloride mass balance method for reliable estimate of efficacy of percolation ponds.