AN EVALUATION OF SEDIMENT YIELD EVOLUTIONS FOR DIFFERENT SUB-CATCHMENTS AND LAND USE TYPES IN THE YANHE RIVER WATERSHED, LOESS PLATEAU

A GIS-based dynamic sediment yield model based on the USLE equation was established to investigate sediment yield evolutions in an easily-eroded watershed of the Loess Plateau from 1995 to 2012. Results indicate that: 1) the dynamic model considering annual changes of precipitation and land management can be used as an effective tool to evaluate sediment yield levels of the Loess Plateau; 2) The annual sediment yield in the Yanhe River watershed has an overall decreasing trend, the average sediment yield modulus from 2009 to 2012 was 1013.3 t/km(2).a, it decreased by about 80.7% compared with the early governance period (1995-1998). The river banks are the main spatial source areas of sediment peak value in the whole Yanhe River watershed, effects of soil and water reduction were significant in the Yanhe River upstream basin and the Xingzi River basin; 3) The sediment yield intensity in 2010 presented an overall increasing trend compared with 1995, the intensity of sediment yield modulus is still increasing for the high intensity of rainfall erosivity. The contribution rate of sediment yield (239-452 t/hm(2)) in water area dramatically increased to 80.8% in 2010. Results may provide scientific reference for the ecological environment planning of the Loess Plateau.