Management of Aquifer Rechange and Subsurface Storage

Abstract

The unregulated development of groundwater, particularly of hard rock aquifers in arid and semi-arid areas, has resulted in a continuous decline of water levels over an area of about 340,000 km2. Out of total annual precipitation of 4000 × 109 m3 in India, about 1240 × 109 m3 is annually lost as surface runoff. It has been estimated that 872 × 109 m3 (bcm is further used for 109 m3) water is still available for recharge and it is feasible to have subsurface storage of 214 bcm. As part of this total feasibility, India plans to have subsurface storage of 36 bcm by constructing about 230,000 small and simple recharge structures such as percolation tanks, check dams, subsurface dykes, etc. The present case study pertains to the over-exploited unconfined aquifer, wherein the average water has declined by 10.5 m since 1972. In this project a 295 m long trench with 30 vertical shafts 2 to 3 m in diameter have been constructed to store 4.79 × 109 m3/year of the surplus monsoon water. The impact analysis showed considerable improvement in yield of the running tube wells, a rise in water level and the possibility to install 130 additional shallow tubewells.