Impact of Open Pit Coal Mine on Groundwater Recharge: Alternative Method for Environmental Assessment

Abstract

Coal mines are widespread in Indonesia. It is primary energy sources for Indonesian electricity, which also contributes to the national revenues even during the Corona Virus Disease (COVID-19) pandemic. On the other hand, groundwater is also one of the important resources in Indonesia. It is commonly utilized for domestic water supply including drinking water, irrigation, municipalities, and industries. Mining with an open-pit system or surface mining is regarded as an activity that affects environmental deterioration. The impact on groundwater including a decrease in the quantity of groundwater is a common and significant issue concerned. According to environmental regulations in Indonesia, each mining company is obliged to submit Environmental Impact Assessment (EIA) documents before starting the mining production to protect and manage the groundwater in mine areas. The objective of this study is analyze the impact of coal mining on groundwater recharge using a water balance approach as a part of EIA. Water balances, before and during mining operation, should be evaluated based on natural hydrological conditions in the land around open pit coal mine areas. Hydrologic data, such as precipitation (P) and temperature, combined with topographic data, were collected to calculate the evaporation-transpiration (ET) and run-off (Ro) values. Then, groundwater recharge (U) was determined by a water balance equation (U=P–ET-Ro). The results of this study showed that the groundwater recharge before mining operation was 1,038 mm, while the recharge during mining operation was estimated to be 947.5 mm. Decreasing the recharge value during mining operation would influence the total amount of groundwater in the aquifer storage around the mine area. Therefore, open pit coal mine would give significant impacts on groundwater quantity.