Change Characteristic of the Runoff and Sediment Under the Similar Precipitation Condition in the Beiluohe River

The impact evaluation of land use change on runoff and sediment change are analyzed based on the paired-year with similar precipitation that was the major sources of runoff and the power of soil and water erosion.The 8 paired-years with similar precipitation from the observed data of Zhuangtou Hydrology Station of the Beiluo River from 1954 to 1996 are selected according to three criterions as the difference of year over 5 years,the difference of annual precipitation less than 20 mm and in flood season the difference less than 10 mm respectively.Through compared the change of runoff and sediment between each paired-year,analyzed the change characters with time,the trends of runoff,sediment and sediment concentration are discussed carefully.The analysis result showed that compared with 1980 and 1996,the annual runoff,sediment discharge and sediment concentration increased,also the runoff in flood season increased too. But in other periods,the sediment discharge decreased before 1970s,the annual runoff and runoff in the flood season increased but the sediment discharge and concentration decreased.