Contribution of percolation tanks to total aquifer recharge: the example of Gajwel watershed, southern India

Jérome Perrin1,*, Cédric Mascré1, Sylvain Massuel2, Shakeel Ahmed3

1BRGM, Indo-French Centre for Groundwater Research, Uppal Road, Hyderabad, India
2International Water Management Institute, c/o ICRISAT Patancheru 502 324 Andhra Pradesh, India, now:  CSIRO L&W, Private Bag 5, Wembley 6913, WA
3National Geophysical Research Institute, Indo-French Centre for Groundwater Research, Uppal Road, Hyderabad, India
*corresponding author: je.perrin@brgm.fr, perrin@ngri.res.in

Abstract

Hard rock aquifers located in semi-arid climatic conditions are especially prone to overexploitation because of limited storage and recharge. In Andhra Pradesh (southern India), such geological and climatic settings prevail and rapid increase in groundwater abstraction for irrigation has led to aquifer overexploitation in many districts. As a response to overexploitation, Central and State governments have launched watershed development programmes aiming at augmenting aquifer recharge using different man-made structures such as percolation tanks, check dams, defunct dug wells.

The objective of the present study is to determine the contribution of percolation tanks to the total aquifer recharge in a typical semi-arid hard rock watershed of southern India (Gajwel, 84 km2) and develop a simulation tool to test the impact of various climatic scenarios/tank management strategies on tank percolation fluxes and overall groundwater balance. The modelling approach consists in a first component which simulates runoff and natural recharge from daily rainfall and evaporation time series as well as volumetric storage in tanks as a result of runoff. A second component computes deep percolation from tanks based on a tank water balance approach. The model is validated by field observations in part of the watershed (temporal variations of tank volumetric storage) and an indirect calculation of total aquifer recharge based on a groundwater balance computation at watershed scale.

Results show the limited contribution of tanks to aquifer recharge and the need for implementation of demand-side management measures to ensure sustainability of the groundwater resource.

Keywords: tanks; hard rock aquifer; semi-arid climate; water management; model; India