Development and Management of Base Flow of a Sand-dominated Alluvial Aquifer of a Large Ephemeral River for Drinking Water Supply in Semi-arid and Fluoride Affected Areas: Example of the River Mayurakshi, Birbhum District, West Bengal, India

摘要

Semi-arid tropical regions in India and elsewhere face major challenges in the management of public water supply for drinking purpose. In such regions knowledge on base flow availability in major rivers is important in development of water management strategies and estimation of small to medium water supplies especially for semi-arid conditions where groundwater is contaminated with fluoride at variable depths. This study focuses on identification, exploitation and utilization of the unexploited base flow of the river Mayurakshi between Md. Bazar in the west and Sainthia in the east in Birbhum district, West Bengal, by understanding the subsurface hydrogeology of the river as well as a proper knowledge of the water budget, water resources in storage, and water quality. Exploratory drilling on the river bed revealed two aquifer settings: unconfined in the west, and semi-confined in the east. Water level is shallow occurring within 2 m below ground level. The sands of the unconfined aquifer are mostly coarse and that of the semi-confined aquifer are medium to coarse. The transmissivity values reveal that the potentiality of the aquifer in the western stretch of the river is higher than that of the eastern stretch. Water supply systems that can be constructed below the river are bed-mounted infiltration gallery and collector well with radials. Water quality does not exceed the permissible limit of Indian Drinking Water Standard except for manganese, iron and colliform bacteria. Therefore, the water needs to be treated for these parameters before supplying to the communities for drinking purpose.