Responses of the hydrological regime to variations in meteorological factors under climate change of the Tibetan plateau

Meteorological factors and the hydrologic cycle of the Tibetan plateau (TP) significantly influence the water resource supply, ecology, and social economy of wide downstream areas in Asia. This study evaluates changes in meteorological factors (e.g., precipitation, air temperature, and snowfall) and corresponding responses in the hydrological regime under future climate change scenarios in both the TP and the downstream areas. The Lancang River basin (LRB), located in the southeast TP and known as the upper Mekong River basin, is selected as the case study area. Future climate change projections are derived from five independent GCMs of CMIP5 and their multi-model ensemble. The variable infiltration capacity (VIC) distributed hydrological model is used to generate streamflow projections in future scenarios. Results show that precipitation and air temperature in both the lower LRB (representing the downstream area of TP) and upper LRB (representing the area in TP) are expected to increase substantially in the future, with higher increments in air temperature found in the upper LRB under high-emission scenarios. Snowfall, snow water equivalent (SWE), and snowmelt are commonly found to decrease with increasing air temperature, and the snow melt time tends to be earlier. Significantly increasing mean and extreme streamflow caused by increasing precipitation are anticipated in the future. The low flow shows much higher relative increments at the upstream of TP, which is mainly caused by changes in snow regulating (decreased snowfall and earlier snowmelt). However, those effects show weak influence on the streamflow in the downstream area, which would be more largely impact by the local precipitation change. In the future, irrigation, hydropower, and navigation in the TP could benefit from increased low flow in the TP, but the consistently increasing extreme high flow may indicate greater flood risk in the TP and downstream areas.