Warming and human activities induced changes in the Yarlung Tsangpo basin of the Tibetan plateau and their influences on streamflow

Abstract

Study region: The Yarlung Tsangpo Basin (YB) on the Tibetan Plateau. Study focus: Characteristics and changes of air temperature, precipitation, snow cover, snow depth, glacier, streamflow during 1979–2015, land cover/use in 1990 and 2015, and the responses of streamflow to the changes are analyzed. The objective is to understand the major factors that influence streamflow in the YB at both intra-annual and inter-annual time scales. New hydrological insights: The YB experiences significant warming but spatiotemporally varying precipitation changes. Snow decreases and glaciers retreat in the YB but with heterogeneous spatial patterns. Streamflow shows strong annual and decadal variability. In the cold and dry season, streamflow is positively correlated to air temperature in the upper sub-basin non-significantly; whereas in the warm and wet season, precipitation influence dominates the streamflow changes in both high and low elevations. Human activity induced 2-fold residential area and 5-fold tree nursery area expansions come at the expense of cropland, dense forest and grassland. In the upper sub-basin, snow depth and streamflow display significant concurrent and lagged correlations for several months. Streamflow in April–May, a melting and seedling season, is positively affected by snow depth of the previous year. Warming induced degradation in cryospheric elements, low precipitation during the cold and dry season, together with land cover/use change could result in water resource conflict in April - May for the YB. Keywords: Yarlung Tsangpo Basin, Environmental change and impacts, Streamflow, Water resources conflict