Effects Of Soil And Water Conservation Measures And Evaluation Of Comprehensive Management Of Small Watershed In Chongqing

Chongqing is located in eastern Sichuan mountain and hilly areas, with a total area of 82400 km2.60%,30%,10% of total area are mountains, hills, plain respectively. Chongqing is a typical mountain hill area and regional eco-fragile area. Chongqing also is an ecological environment protection area of Three Gorges Reservoir. Unreasonable development activities of human caused serious soil erosion, non-point pollution, and enormous ecological security threat. Systematic classification of soil and water conservation measures, effects analysis of soil and water conservation measures and evaluation of soil and water conservation paradigm are important basis for selecting measures, planning and designing, and also have an important significance in soil conservation ecological environment construction. According to soil erosion and soil conservation characteristics of Chongqing, presented a classification system based on controlling objects for soil and water conservation measures.This paper quantitatively analysis the typical effects of municipality water conservation measures, changes of factor C values and factor P values under different measures based on the Universal Soil Loss Equation(USLE). According to sustainable management of watershed and the soil erosion's decrease proportion based on USLE model, it given a paradigm for evaluation of small watershed management. The major results are as follows:(1)According to the controlling objects, Chongqing soil and water conservation measures were divided into four categories, small watershed comprehensive management measures, regional soil and water conservation measures, special soil and water conservation measures and soil and water conservation measures for development and construction project. The establishment of classification of Soil and water conservation measures at different spatial scales can make a more direct and positive response from the external constraints, and also achieve the goal of soil conservation ecological environment construction.(2) In the soil and water conservation measures in Chongqing, terrace sediment reduction efficiency is 8.4%, sediment reduction efficiency of ridge culture and intercropping in agricultural practices are 41.67%-68.00% 17.78%-45.99% respectively, and intercropping treatment honeysuckle 17.2%; Compared with terrace, tillage,the sediment and water reduction efficiency of plant measures is higher than 75%.It indicated that plant measures has the most obvious efficiency for sediment and water reduction. The efficiency of water and sediment reduction of ecological restoration measures are 42% and 61% respectively. Analysis of soil improvement by different soil and water conservation measures shows that vegetation can significantly improve soil structure, increase soil fertility, and soil infiltration. The derivation of the model and numerical indicated that factor P value and benefit of sediment reduction of soil and water conservation measures are opposite to each other, and the value can be used for soil erosion prediction based on USLE model.(3)According to the observation of runoff plots, rainfall erosion and sediment yield characteristics of different sloping cumulative show that:wasteland (HS-1)>downslope cultivated farmland (HS-2)> cross slope farmland (HS-3)>cross slope farmland hedgerows (HS-4);using USLE model to calculate C values of tillage downslope, cross slope and cross slope farmland hedgerows are 0.174,0.168 and 0.129, while the downslope, cross slope and cross slope farmland hedgerow P values are 0.78,0.58 and 0.51;P-values of measured data of the cross slope and cross slope farmland hedgerows are 0.69 and 0.65,It shows that both the model values and measured value can reflect laws of P factor changing in purple hilly area of water conservation measures, that is downslope cultivated land> cross slope farmland> cross slope farmland hedgerows.(4) Soil Loss intensity due to vegetation cover, cropping systems, cropping patterns and crop types and other factors vary widely; through investigating the C value, P value changes in the years of different cropping patterns,we can choose suitable crops, cropping systems, cropping patterns, and increase surface coverage during the rain season. It can effectively control soil erosion and reduce land degradation and provide basic parameters for soil erosion prediction model.(5)Xianyu watershed sustainable development degree is 0.641 in 2007.It indicated small watershed management works have entered the state of sustainable development; In terms of contribution of index, resources and environment carrying capacity of 2009 is 15.55% significantly higher than that in 2007, and economic development capacity is 10.95% higher than that in 2007.Based on USLE model the reduction proportion of soil erosion shows that ratio of reduce soil loss in small watershed is 28.19%, ratio of reduce soil loss in all soil conservation measures are as follow:Terrace is 1%,water and soil conservation forest is 15.03%,economic fruits is 11.25%, blockading administration is 32.91%;The proportion of soil loss reduce increases with the slope and slope length,The ratio of reduce soil loss of slope under 25°has a more moderate trend, The ratio of reduce soil loss of slope above 25°has a more steep trend; when the slope length is longer than 70m,the ratio of reduce soil loss has more moderate trend, otherwise it has a steep trend. The small watershed management could make a reference and paradigm for similar small watershed treatment.