Groundwater model using finite difference method on open-pit coal mine in West Aceh Regency, Nanggroe Aceh Darussalam, Indonesia

Abstract

The change of land use caused by mining operation indeed affect the availability of groundwater that exist in the surrounding region. Especially mining operation that used open-pit methods for its operation. Open-pit mine is a surface mining technique that extracts coal by removing the overburden that conceals the coal itself. By removing the materials located above the coal, it will indeed affect the hydrology condition of the region whether it is the groundwater elevation or groundwater availability of the surrounding area because some aquifer were cut in the process that leads to groundwater disturbance.. This condition indeed reflects the condition of the research model area in Meureubo, West Aceh Regency. Geologically, the formation that exists in the research area is tutut formation which has dip<10o in the direction of the southwest. The hydrogeological boundary of the model is two big rivers located in the west of the model (Nagan river) and the river in the northeast of the model. The model consists of 5 layers in total that include 2 layers as aquifer (sandstone) and 3 layers as an aquitard. Those aquifer is separated by a clay layer which functions as an aquitard in this model. The goal of this research is to create a model that resembles the impact on the groundwater condition in the research model caused by the coal mining activity that will be held years from now on. To achieve that goal, knowing the hydrology and hydrogeology condition of the area is critical in order to create an accurate model that show the groundwater condition before and after the mining activity. The model will be created using the finite difference method, which is a numerical simulation in MODFLOW. The results of the research will show the groundwater fluctuation around the location of the mining activity and also in the mine location itself. From the analysis that had been done, the results show that there is a decrease in groundwater level elevation in the pit area for about 8 meters in 10 years based on the mine plan design and 3-5 meters in the settlement around the mining area. The change in groundwater elevation was caused by the removal of an aquifer that happened during the mining progress.