DECOUPLING STREAMFLOW RESPONSES TO CLIMATE VARIABILITY AND LAND USE/COVER CHANGES IN A WATERSHED IN NORTHERN CHINA

Restored annual streamflow (Q(r)) and measured daily streamflow of the Chaohe watershed located in northern China and associated long-term climate and land use/cover data were used to explore the effects of land use/cover change and climate variability on the streamflow during 1961-2009. There were no significant changes in annual precipitation (P) and potential evapotranspiration, whereas Q(r) decreased significantly by 0.81mm/yr (p<0.001) over the study period with a change point in 1999. We used 1961-1998 as the baseline period (BP) and 1999-2009 the change period (CP). The mean Q(r) during the CP decreased by 39.4mm compared with that in the BP. From 1979 to 2009, the grassland area declined by 69.6%, and the forest and shrublands increased by 105.4 and 73.1%, respectively. The land use/cover change and climate variability contributed for 58.4 and 41.6% reduction in mean annual Q(r), respectively. Compared with the BP, median and high flows in the CP decreased by 38.8 and up to 75.5%, respectively. The study concludes that large-scale ecological restoration and watershed management in northern China has greatly decreased water yield and reduced high flows due to the improved land cover by afforestation leading to higher water loss through evapotranspiration. At a large watershed scale, land use/cover change could play as much of an important role as climate variability on water resources.