Water resource accounting for a mining area in India

A water resource accounting study has been carried out for a limestone mining area located in Thondamuthur block of Coimbatore district under Tamilnadu state in India. The major source of surface water in the region is south-west and north-west monsoons during July-August and October-November, respectively. During the winter season, groundwater levels range from 13 to 25 m below the surface whereas during the summer season it varies from 20 to 30 m. The thickness of the weathered zone ranges from 10 to 40 m and the depth to bedrock ranges from 50 to 55 m. The groundwater is generally potable. The average annual rainfall during the twelve-year period (1988-1999) is 590 mm. Out of the total rainfall, around 11% is lost as surface runoff, 10% is lost through evaporation and transpiration, 30% is utilized for consumptive used, 16% is absorbed as subsoil loss and remaining only 33% is stored as groundwater recharge. Again out of total groundwater recharge only 85% is utilizable groundwater. The annual utilizable groundwater resource available in the area is 79.220 million cubic metre (MCM). Whereas, total groundwater demand for the region is 68.922 MCM, and breakup of industrial, domestic and agricultural demands are 0.020, 5.956 and 62.946 MCM, respectively. Therefore, at present the stage of groundwater development or utilization for the area is around 87%, and falls under 'Dark' category. The 'Dark' category indicates that the utilization of groundwater is more than 85% of available groundwater resource. This situation has to be controlled by immediate initiation of suitable measures for groundwater recharge. The identified recharge zones in the block along with the recommended recharging methodology are summarized in this paper. The paper includes a comprehensive site description, status of the water resource and demand, identification of recharge zones and recharging techniques, and recommends a water supply augmentation strategy for enhancement of water resources in the region.