Annual Variation Characteristics of Sediment Yield on the Loess Plateau

Annual variation characteristics of sediment yield on the loess plateau are analysed by using 16 feature indexes,and the annual variation characteristics of sediment yield in different regions and watersheds are obtained.The result showed that the annual average sediment yield(1955～1986) on the loess plateau was 15.2×108t,the maximum sediment yield was 32.83×108t(1958),the minimum was 4.96×108t(1965),and the ratio between maximum and minimum was 6.62,between maximum and average was 2.16,the coefficient of variation was 0.56.On the loess plateau,there are 12 years in which sediment yield is more than average value,and 20 years in which sediment yield is less than average value,the proportion in the total years is 37% and 63% respectively;the sediment yield of more than average is 277.85t,the sediment yield of less than average is 208.52t,the percentage in the total sediment is 57% and 43% respectively.In the 32 years,the years in which sediment yield equals to less than 0.5 times,0.5～1.0 times,1.1～2.0 times and 2.1～3.0 times of the average sediment yield are 6,15,8 and 3 years;the propotion in the total years is 18.8%,46.8%,25.0% and 9.4% respectively.