Effects of climate variation and land use change on runoff-sediment yield in typical watershed of loess hilly-gully region

In order to explore the impacts of climate variation and land use change on runoff and sediment yield, and to understand the variation pattern of land use and water resources in the Loess Plateau region, the Luoyugou Watershed in loess hilly-gully region was selected as the study object. Mathematical statistics method, double mass curve and grey correlation degree analysis were applied to analyze the variation trends of annual precipitation, annual runoff and annual sediment yield in the period of 1986- 2008. A multi-year average water balance model was used to quantify the respective contribution of climate and land use change to the reduction of runoff and sediment yield. Brief conclusions could be drawn as follows: 1) precipitation in the Luoyugou Basin did not show an obvious tendency (P =0.22), whereas annual runoff and sediment yield showed a downtrend (P =0.025 and P =0.087, respectively) from 1986 to 2008 with an abrupt change identified in 1994. 2) Besides the rainfall, potential evaportranspiration and sunshine hours were main impacting factors on the runoff and sediment reduction, respectively. 3) The contribution rate of climate variation to runoff-sediment change reached 33.1% and 32.5%, respectively, while that of land use change reached 66.9% and 67.5%, respectively.