Assessment of effect of recharge from a check dam as a method of Managed Aquifer Recharge by hydrogeological investigations

Check dams are often used as a method of Managed Aquifer Recharge (MAR) and are generally preferred in non-perennial rivers for intentional storage of the water. The objective of this study is to evaluate the efficacy of a check dam constructed as a MAR initiative across Arani River, North of Chennai, India by long-term hydrogeological investigations. Electrical resistivity survey and drilling of borehole helped to understand the subsurface geology. Water level and water quality measurements were carried out periodically from July 2010 to May 2012. Groundwater occurs in unconfined condition in the alluvial formations extending up to a depth of about 50 m below the ground surface. Water table is at a depth ranging from 3 to 12 m below the ground level. The electrical conductivity and concentration of major ion were less in water stored in the dam and hence the recharge of this water has led to improvement in groundwater quality. Rainfall recharge of this study area was estimated to be about 17 % of annual rainfall. About 63 % of water stored in the check dam resulted in groundwater recharge. This has led to an increase in groundwater level from 1 to 3.5 m until a distance of about 2 km. The cost of 1 m³ of water stored by the check dam will be Rs. 1.20/-. The comparison of groundwater level, water level in the check dam and water quality assisted in demarcating the areas benefited by the storage of water in the check dam. Thus, the electrical conductivity and major ion concentration of water, which are inexpensive, rapid and easy to measure, were used as a tool for understanding the area that is benefited by the water stored in the check dam. The study brought out the efficiency of check dam as a method of MAR in improving the groundwater recharge and groundwater quality.