Multi-temporal scale changes of streamflow and sediment discharge in the headwaters of Yellow River and Yangtze River on the Tibetan Plateau, China

Abstract The changes of water and sediment discharges in the headwaters of large Asian rivers have increasingly become a hot issue. This study investigated the streamflow and sediment discharge changes in the headwaters of Yellow River Basin (YRB) and Yangtze River Basin (YARB) by using long-term hydro-meteorological data from 1956 to 2012. The nonparametric Mann–Kendall test, Pettitt test, cumulative anomaly curve (CAC), and double cumulative curve (DCC) were used to identify trends and change points of the hydro-meteorological variables and quantify the response of streamflow and sediment discharge to climate change and anthropogenic activities. The results are as follows. (1) Slightly decreasing trend in streamflow and increasing trend in sediment discharge were detected from 1956 to 2012 in the headwater of YRB. Meanwhile, both streamflow and sediment discharge in the headwater of YARB showed increasing trend. Change-point analyses further revealed that turning (transition) years existed and the abrupt decline in streamflow and sediment discharge began in 1989. (2) The specific sediment yield–runoff depth and sediment concentration–streamflow relationships in the two basins could be well fitted by the power function on the annual, flood season, and monthly scales. Sediment productive ability of runoff during the flood season was much greater than that over the full year. (3) The headwater of YRB contributed huge amount of water resources and very little sediment to the downstream, however, the headwater of YARB had little influence on downstream. (4) Compared with the baseline period (1956–1989), precipitation reduction played a major role in the streamflow and sediment discharge reductions in the post-baseline period (1990–2012). Given the scarcity of soil and water resources, anthropogenic and climatic impacts on streamflow and sediment discharge must be given more attention in the future.