干旱区生态环境知识资源中心

The concept of groundwater recharge and quality improvement is often implemented in arid and semi-arid areas with depleted aquifers. Nalgonda district in Andhra Pradesh, India, has endemic fluoride, with concentrations in drinking water varying between 3 and 8 mg/l. Numerous techniques adopted in the recent past for defluoridizing groundwater proved to have limitations. The integrated approach of a geographic information system (GIS) and an analytic hierarchy process (AHP), to identify suitable sites for recharge structures over an area of 115 km(2), is highlighted. Further, to validate the delineated sites, a micro-watershed basin (2 km(2)) was selected for detailed recharge assessment and site feasibility studies through geophysical and tracer tests. Groundwater velocity (7 m/day) and flow direction through fractures in the shallow horizon were established through tracer experiments. The efficacy of the recommended recharge structures and their impact on groundwater quality were assessed over a period of 5 years, from 2002 to 2007, and the mean groundwater fluoride concentration of > 3.5 mg/l over the study area was brought down to < 1.5 mg/l.