Study On Variation Characteristics Of Water And Sediment And Sediment Reduction Benefits Of Water And Soil Conservation In Zuli River Basin

Zuli River is a primary tributary on the right bank of the upper reaches of the Yellow River, the watershed has strong soil erosion, easily fragile ecological environment, and serious soil erosion not only restrict the sustainable development of the local economy and society, but also a great threat to the lower reaches of the Yellow River for people’s life and production. Therefore, the study on water and sediment change characteristics and conservation benefit are the foundation of soil and water erosion control effectively. In this study, selecting the Zuli River Basin as the research area and based on the monitoring data. The method of Mann-Kendall was used to analyze the rainfall in Zuli River Basin and the change trend of runoff and sediment. The relationship between water sediment variation and influenced factors were analyzed by using the SPSS20.0 software, and used "hydrologic method" and "water conservation method" to study the water and sediment reduction benefits of soil and water conservation measures, the role played of water and sediment reduction were discussed by soil and water conservation measures in Zuli River Basin. The following main conclusions were obtained:(1) Zuli River Basin rainfall’s trends and characteristics are very similar with the flood season rainfall, it has large inter annual variation, showing the trend of decreasing year by year. Base on average annual rainfall, the period was divided into two periods for wet and dry. The abundant water period(1955-1989) annual precipitation is 376.2mm, dry period(1999-2013) the annual precipitation is 224.9mm.(2) Zuli River Basin Rainfall, the sediment of the runoff has the same change rules and characteristics, it has large inter annual variation, showing the trend of decreasing year by year. According to the reliability value of UFk variation characteristics, the changes of sediment runoff is divided into four times: non significantly reduced(1955-1971), significantly reduced(1972-1985), more significantly reduce(1986-2000), extremely significantly reduced(2001-2013).(3) Annual rainfall, flood season rainfall has more correlation between annual sediment runoff yield, there were extremely significant correlation between cumulative annual rainfall and runoff transport of sediment accumulated value, its cumulative value was used to simulate and it has better reliability when in prediction of runoff and sediment.(4) Respectively used by "hydrologic method" and "water conservation method" calculation of reducing water and sediment efficiency under soil and water conservation measures, two kinds of calculation methods have some certain errors, the "hydrologic method" of double cumulative curve method calculation results was more accurate, the benefits of water reduction reached 37.93%, sediment reduction benefit reached 70.92%. "Water conservation method" of calculation for soil and water conservation was slightly less than "hydrologic method", the benefits of water reduction reached 35.82%, the benefit of sediment reduction reached 40.13%.(5) The level terrace played the most important role in the contribution of the soil and water conservation measures to the benefit of water and sediment reduction.