Regional runoff variation and its response to climate change and human activities in Northwest China

Water resource problem is a challenging area of research in arid and semiarid regions of the world. In this paper, historical runoff data of 36 rivers in Northwest China (NWC) were used to assess regional water resource change. Furthermore, eight of the river basins (with different runoff recharge source) were also selected as typical regions to further analyze the causes of runoff change, based on the data of climate change and human activities. The result showed that headwater runoff in rivers of eastern part of NWC was decreasing in the last 50 years, while it was increasing in the western part oppositely. Temperature rising was the main reason for “runoff decreasing,” and “runoff increasing” was mainly the comprehensive result of plentiful precipitation and increased melt water caused by global warming. The 1990s was a common runoff turning period of upstream rivers in NWC as the reason of climate change. The differences of climate condition and runoff recharge source greatly affected runoff processes in the upstream of each river within a year, while the processes in the middle and lower reaches of most rivers in NWC were relatively smooth because of agricultural irrigation consumption and runoff regulation by water conservancy projects. Analyzed by rescaled range analysis method, upstream runoff in rivers of eastern NWC will continue to decrease, while it will increase in other regions when the climate change holds the current trend in the next few decades. Runoff change in midstream and downstream is not clear as it mainly depends on economy structure and level.