Temporal and spatial variation of the main water balance components in the three rivers source region, China from 1960 to 2000

The three rivers source region (TRSR) is the most sensitive region of global climate change in China. The temporal and spatial variations of main water balance components (precipitation, snowmelt, actual evaporation, runoff, etc.) during the period from 1960 to 2000 in the TRSR were analyzed by hydrologic simulation and statistical detection. The results showed that: when compared with the components in 1960s, (1) the variation of precipitation from 1970s to 1990s was not significant in the whole TRSR though it increased slightly in the Yellow River Source Region (YeSR) and Yangtze River Source Region (YaSR), but decreased slightly in the Lancang River Source Region (LcSR); (2) the snowmelt increased in most regions of TRSR except the downstream of YeSR and YaSR, but the trend was statistically significant only in the YeSR; (3) the actual evaporation increased continually in the whole TRSR, but the trends were significant in the middle stream of the YeSR and YaSR, and the YeSR was the greatest; (4) Although the runoff depth decreased gradually in the TRSR, the trends were significant only in the middle stream of the YeSR and YaSR and the YeSR was the greatest. Inevitably, the discharge decreased in the TRSR but the trend was not statistically significant. Climate change (i.e., the slightly decreasing of precipitation and the increasing of air temperature) was the most important factor to affect the variations of water balance components. The most sensitive region to climate change was YeSR, followed by YaSR, and the least one was LcSR. This study was expected to provide the foundation and a reference to analyze the water resources evolution and test the climate change impacts in TRSR as well as the whole China.