3-D numerical groundwater flow simulation for geological discontinuities in the Unkheltseg Basin, Mongolia

Groundwater models which realistically represent the hydrogeology of a complex system, like the Unkheltseg Basin, are critically important to Mongolia. They have flow on benefits to research, governments, management strategies and commercial development within the country. Limited case studies of calibrated 3-D numerical transient simulations in fault-controlled connection between basins, similar to the Unkheltseg Basin, are available in the public domain and the model presented here aims to address this problem. This basin is uniquely geologically controlled and a key water supply resource for future economic development in the Taikh Valley. Commercial exploration projects have produced the high-quality geological and hydrogeological data gathered, necessary for successful model simulation at a basin-wide scale. Using the “DRAIN Package” and “Fracture-Well Package FW4” in MODFLOW-SURFACT, the spatial discretization necessary to fully represent horizontal and vertical flow direction was achieved to effectively constrain recharge and discharge across the fault barrier. This model is an important tool for establishing a long-term monitoring programme in a fault-controlled basin, which predicts regional impacts, both short and long term.