Investigation of sediment transport balance in the Guanting Reservoir watershed indicated that in the past fifty years,the total sediment yield resulting from soil and water loss was 4.565 billion tons.Soil and water conservation measures kept about 0.771 billion tons,16.89% of the total sediment yield.Water conservancy projects retained about 0.765 billion tons,16.76% of the total sediment yield.Irrigated lands intercepted about 0.965 billion tons,21.14% of the total sediment yield.River beds and courses accepted about 0.816 billion tons,17.88% of the total sediment yield.The reservoir trapped about 0.75 billion tons,18.02% of the total sediment yield.The reservoir discharged about 0.425 billion tons,9.31% of the total sediment yield.The amount of sediment retention by soil and water conservation from 1981 to 2000 increased about 26.27% in comparison with that from 1950 to 1980,which indicates that sediment retention has increased significantly in the recent 20 years.