Spatial distribution of Cesium-137 and characteristics of soil erosion were studied using 137Cs trace technology in the Yangwa watershed on the Loess Plateau of the southern Ningxia Hui Automous Region.The 137Cs inventory was 1 966.99 Bq/m2 in the watershed.Special activities of 137Cs were different in plough layers under different land uses.It could be expressed by an exponential function for the soil profile of forest and grassland and by a uniform distribution for the soil profile of sloping land.In terms of area activities of 137Cs

tableland

forest and grassland

and sloping land were ranked in descending order.Sedimentation and soil erosion on cultivated sloping land and tableland had a great variance

with the variation coefficient being over 65%.The change trends of soil erosion module and distribution of 137Cs were adverse

but both of them were distributed as a strip or patch under different land uses.The moderate and serious erosion types were the main types of soil erosion and their area accounts for 46% of the total area of Yangwa watershed.Therefore

controlling soil erosion on sloping land is the key to the watershed management.