What drives the water quality changes in the Selenga Basin: climate change or socio-economic development?

Lake Baikal is the largest near-surface global freshwater source and of high interest for water quality alterations, as deterioration of water quality is a main global and an increasing issue in the Selenga River Basin. Here, the Selenga River Basin as main contributor to the inflow of Lake Baikal is extremely important. Pressure on ecosystems and water resources increased due to population growth, rapid urbanization and rising industrial activities, particularly in the mining sector. In this study, the large-scale water resources model WaterGAP3 is applied to calculate loadings of conservative substances (total dissolved solids) and non-conservative substances (faecal coliform bacteria and biological oxygen demand) in a spatially explicit way as well as in in-stream concentrations to get an insight into the state of water quality under current and future scenario conditions. The results show a strong increase in loadings in the scenario period and consequently increasing concentration levels. Comparing the sectoral contributions of the loadings, domestic and industrial sectors are by far the main contributors today and expected to be in the future. Furthermore, for all modelled substances and time periods, water quality thresholds are exceeded posing a potential risk to aquatic ecosystems and human health.