Impact of various anthropogenic disturbances on water availability in the entire Mongolian basins towards effective utilization of water resources

In Mongolia, overuse and degradation of groundwater is a serious issue. The authors have recently applied a process-based eco-hydrology model, NICE (National Integrated Catchment-based Eco-hydrology) to urban and mining hubs to explicitly quantify spatio-temporal variations in water availability. In this study, NICE was scaled up to the total of 29 river basins in the entire country. The model simulated the effect of past climatic change and human activity on water resources during 1980-2018 there. The model reasonably reproduced observed river discharge with a maximal value during summer rainfall seasons. The simulation also revealed heterogeneous distributions of hydrologic budget and its response to climatic and anthropogenic disturbances. In addition, the authors detected hot spots of groundwater degradation by anthropogenic activity in the national scale. Analysis of relative contribution of environmental factors further clarified the characteristics in these areas and quantified spatio-temporal trends in groundwater level due to the effects of changes in precipitation and various water uses. Generally, the result showed changes in precipitation had a large effect on changes in groundwater levels until 2000. In contrast, the model clarified human activities have recently had a large impact on groundwater level changes. This trend was particularly conspicuous in river basins with urbanization and mining development such as Orkhon, Kharaa, Tuul, Galba, Ongi, Altain Uvur Govi, and Taats River Basins. This methodology is powerful to resolve future competition for water resources in areas with fewer inventory data that could potentially trigger conflicts between urban, mining, industry, herders and local communities.