Effect of recharge from a check dam and river bank filtration on geochemical and microbial composition of groundwater

Abstract

Check dams are often constructed across the rivers to store excess runoff and to improve groundwater recharge. Quality of groundwater around the check dam depends on the chemical and biological characteristics of the water stored in the check dam. The aim of this study is to determine the benefits due to changes in chemical and microbial composition of groundwater during the process of recharge. This study was carried out in and around a check dam constructed across Arani River, Tamil Nadu, India, where people depend on groundwater reserves for domestic and irrigation requirements. Water samples were collected from the river and surrounding wells and were analysed for chemical and microbial contents. WQI based on the chemical composition indicates that the groundwater was good in this area, but microbes such as Escherichia spp., Salmonella spp., Shigella spp. and Clostridium spp. were present. However, the microbial quality of groundwater is far better than the water stored in the check dam. Hence, production wells can be planned at a distance of about 400 m in the east so that the bank filtrate will take at least 60 days to reach the well. This will considerably reduce the microbial load and also the cost of post-treatment. Thus, river bank filtration may be adopted near the check dams so as to maximise well yield and to achieve natural filtration. This will also enable to use a portion of water that otherwise would be lost due to evaporation from the dam.