Influences of climate and land use on streamflow components in Hun-Taizi River Watersheds, Northeast China

Total streamflow can usually be divided into two components, direct runoff and base flow, and the variation of total streamflow is the integration of the changing of the two components. The key impact factors for the two components were different, and hence the long-term variation characteristics of the direct runoff and base flow were of great difference. The Hun-Taizi River Catchments, Northeast China, were regarded as main sources of water supply for agriculture, industrial and domestic use of Liaoning province, China. Climate and land use were regarded as the two main factors influencing streamflow. The observed data show that the total streamflow in the upper reaches of these watersheds was reduced. However, effects of climate and land use on streamflow components in the entire watersheds have not been deeply studied, which undoubtedly affect the management and utilization of water resources in these catchments. In this paper, two non-parametric test methods, Mann-Kendall's test and Spearman's Rho test were used to analyse annual change of runoff and climate variations in the hydrological stations established in the Hun-Taizi River Catchments, Northeast China. Results showed that streamflow components of the Hun-Taizi river catchment decreased under the combined effects of climate change and land use variability, while each factor had different effects on direct runoff and base flow. Mean annual streamflow and its components were positively correlated with mean annual precipitation and woodland coverage; and negatively correlated with temperature and farmland and construction land coverage. The influences of average climate and land use on mean annual direct runoff were more intense than mean annual base flow. Climate variations speeded up the changing rate of annual direct runoff and base flow; and land use changes slowed down the changing rate. Differently from the effects on mean annual values, the influences of long-term precipitation variability and land use changes on base flow were more obvious than direct runoff. Climate changes played more important role than land use variability in affecting long-term variations of annual direct runoff and base flow due to the smaller variability of land use in this catchment. Thus, climate variation should be considered as the dominant factor to evaluate the management and utilization of water resources, hydrological processes and ecosystems in the regions of Northeast China.