Temporal and Spatial Distributions of Water and Sediment Yield in the Luanhe River Basin, China

Water and soil loss is a serious threat in the North China, especially in the Luanhe River Basin, which is considered to cause severe sand hazards in the vicinity of the basin, especially Beijing and Tianjin. To alleviate the hazards, Phase 1 of the Sandification Combating Program has been carried out since 2000, which is intended to affect water and sediment yield of the basin accordingly. The SWAT model was applied to contrast and analyze the effect of the policy on spatial and temporal distribution of the water and sediment yield in the basin before the implementation of the program (1976-1999) and after the implementation of the program (2000-2012) and identify critical zones of water and soil loss to provide valuable information for effectively managing water loss and soil erosion in the Luanhe River Basin. The SWAT model was calibrated against field data from 1976 to 1983 and validated from 1984 to 1991 at five gauging stations in the studied area. Satisfactory results of simulating runoff and sediment yield both in the calibration period (Ens: 0.73-0.92, R-2: 0.73-0.95) and in the validation period (Ens: 0.65-0.87, R-2: 0.73-0.87) were obtained. By the use of the justified model parameters and daily meteorological data from 1992 to 2012, the runoff and sediment yield from 1992 to 2012 were extended by the model in the basin. The results showed that the water and soil loss in most zones of Luanhe River Basin was expectedly serious before the implementation of the sandification combating program (1976-1999). And after the implementation of the program (2000-2012), total water and sediment yield, water and soil loss intensity and erosion area are all significantly decreased. It was also found that water loss in lower zones of the Luanhe River was more serious than that in upper and middle zones. A few upper and middle zones are still experiencing very serious soil erosion. The results also revealed that the critical time period for water and sediment yield is the wet season (June-September), especially in July and August during the two stages. The critical land use types of contributing the highest water and sediment are identified to be respectively the development area and agriculture land in the Luanhe River Basin.