The Benefit Evaluation Of Water And Soil Conservation Measur Of Tuweihe Watershed

China is one of the most serious soil erosion countries in the world. For the loess plateau,hostile ecological environment and serious soil erosion not only limit the local social andeconomic development but also affect the downstream channel and reservoir safety. Integratedwater and soil conservation in river basins is the key to control soil erosion. In addition,studying on benefits of soil and water conservation is the basis of optimizing water and soilconservation measures allocation and further controlling soil erosion. Tuwei River river basinof Yellow River middle reaches was selected as the research object in this paper. Trend,mutation and period rules of hydrological time series like precipitation, runoff and sedimenttransport was all analyzed to study hydrological regime changes in Tuwei River river basin.Meanwhile, a variety of methods was utilized to analyze and evaluate the effects of soil andwater conservation measures on runoff and sediment discharge in Tuwei River river basin.Through comparing calculation characteristics and results of various methods, someconclusions can be summarized as follows:(1)Moving average method, accumulated anomaly method and Kendall rank testmethod were employed to analyze the trend of precipitation, runoff and sediment transport inTuwei River river basin. The results show that annual precipitation and annual sedimenttransport vary greatly between years in Tuwei River river basin. More specifically, annualprecipitation has no significant decreased or increased trend while annual runoff and annualsediment transport have striking reduced trend.Comprehensive analysis on Mann-Kendall test,orderly clustering and Lee-Heghinian method was conducted, annual runoff and annualsediment transport mutation occur in1978and1971respectively. Gini coefficient methodanalysis result indicates that precipitation and sediment transport distribute unevenly withinthe year. Precisely, precipitation and sediment transport mainly focus on July and August,which presents high concentration degree. Besides, annual runoff changes little between yearsand it is relatively well-distributed within the year.(2)According to precipitation and runoff data in Tuwei river basin from1956to1978,double cumulative curve method, base flow segmentation method and flood seasonsegmentation method were utilized to compute runoff efficiency and sediment efficiency of soil and water conservation measures after the year of1978by means of taking1978and1971as the boundary respectively. The results demonstrate that runoff and sediment reduceabout20×108m3and3.5×108t from1979to2005and from1972to2005separately due towater and soil conservation measures effect. From this perspective, runoff benefit of soil andwater conservation measures is approximately60%while the counterpart of sediment isaround45%.(3)By comparing various computing methods, soil and water conservation benefit errorwith double accumulate computation method is much larger. As for precipitation and sedimenttransport relation technique, the correlation is lower and it also has the minimum calculationresult. By contrast, the calculating result of base flow segmentation method is much closer toreality. Using sediment concentration to calculate sediment benefit has the similar result, thereare still many problems need to be studied further though.Runoff efficiency has a decreasingtrend along with the increasing terrace and grassland area. It demonstrates that the biggestcontribution to runoff benefit is dam field and the forest land takes second place. With theincreasing terrace area, sediment benefit shows a decrease trend similarly. Here the grasslandcontributes most to sediment benefit while the dam field benefit takes second place.