Model Study of Basin Soil Loss (BSL) in the Loess Plateau of China (Ⅰ)

Rain is the main motive force of erosion in the Loess Plateau of China. The relationship between rain and basin soil loss （BSL） is the base for establishing BSL model. Based on areo image interpretation, site investigation and analysis of 30-year rain-hydrological data of the study area—the Gushanchuan River Basin which is a branch of the middle reaches of the Yellow River basin as well as one of the intense erosion centres, the BSL features have been reveaIed. According to the features, the structure of the BSL model is proposed as follows: C. R=S, where C, R and S represent the factor of underlayer, rain and BSL quantity, respectively.Then by using the methods of multivariate statistical analysis, the dominant rain specific elements that affect the BSL and the corresponding formula of the relationship between rain and BSL have been determined as Pand I, andS=585.80PIrespectively. With this formula the BSL quantity of every rainfall can be estimated. The estimated accuracy can be satisfied after correcting according to the preceding conditions of the rain.