Numerical Modeling of Groundwater Flow in Karst Aquifer, Makeng Mining Area

Problem statement: Making iron ore is one of the largest mining projects in south east of china. Due to the development of mining activities in that site, it has become necessary to increase the depth of exploration. Increase the exploration depth makes the mining tunnels subjected to the karst water inrush. Approach: A hydrological and a hydrogeological model for the Makeng area have been developed, which yield information on relevant parameters such as groundwater recharge and margins’ lateral inflow, to estimate aquifer yield. USGS flow code, MODFLOW 2000, was used to produce the numerical model. Collected GIS based information was synthesized in a finite difference numerical model. The regional steady and transient-state flow was calibrated under pre-development conditions assuming an equivalent porous medium approach. Results: Water budget calculations show that the total groundwater flow in regional aquifers amounts to 2.98 mm³ year^-1. Infiltration from precipitation provides 61.7% of the groundwater supply, while 21% comes from lateral inflow and the remaining 17.3% is induced recharge from surface waters. Discharge from regional aquifers occurs through springs outflow 88.5% and flow to streams 11.5%. Conclusion/Recommendations: Although the karstic nature of the limestone aquifer the equivalent porous-medium flow model is appropriate to represent hydraulic heads and recharge/discharge relationships on a regional scale. The results of this study can be used to predict the required amounts of pumping and the possible locations to dewater the groundwater around the mining tunnels.