Current Situation And Benfits Evaluation Of Check Dams In Northern Shaanxi Province

Northern Shaanxi province locates in the sandy and loess holly gully region, where hash natural environment leads to the chronic poverty for local people's life, and also it confines sustainable economic and social development. Since the reform and opening, with the support of our country, northern Shaanxi has launched ecological construction of water and soil conservation such as check dams building, obtaining obvious ecological, economic and social benefits. Survey and statistical data of check dams in Shaanxi shows that 92.98% check dams mainly distribute in YuLin and YanAn, which makes check dams an important role in the water and soil loss in northern Shaanxi province.Based on the survey of check dams in the collected basin, this paper analyzed each indexes about fundamental, social, economic and ecological benefits of northern Shaanxi, and then calculated each index weight of check dams in northern Shaanxi, and made out existing problems, providing theory basis for the check dam sustainable development. Results showed as follows:The intercepting sediment reservoir capacity of current big and medium check dams in northern Shaanxi is 3.98×10⁹ m³. There is 0.143 check dam average per 1km². Total control area of the single dam of the big and medium check dams is 26750.57km², and average control area of the single dam is 2.50km². Form a macroscopic point, there is a good pair-wise correlation among total building density of check dams, measured intercepting sediment reservoir capacity and total control area of the single check dam.It is a good utilization that there are only 11.74% of the big and medium check dams which have not been used in Yulin city, and dams are mainly used to plant crops , however, there is no more than two crops, so traditional planting patterns should be changed. It is not an ideal utilization that there are 86.62% of check dams which have not been used in Yanan city, and dams are only used to intercept sediment.Big and medium check dams are mainly managed and protected by a collective under contract, which account for 92.29% of the total. Most peasants accept two administration and protection patterns that are leasing and auction, and in future check dams should be managed and protected through leasing and auction.There are only 37% of the big and medium check dams in good condition in northern Shaanxi, and 63% of the check dams are in motion with problems, in which dams with hidden danger in bodies account for 43.66%of the total, dams with hidden danger in drainage structures account for 9.46% and dams with hidden danger in overflow spillway account for 7.67%. Conditions described above shows that the hidden danger in dam bodies is the most serious problem in the safety of big and medium check dams in northern Shaanxi province.The control area of big and medium check dams in northern Shaanxi is 28703.84 km², which accounts for 35.75% of the total land in northern Shaanxi, and total intercepting sediment capacity is 4.11×10¹⁵ kg, which highlights the important role of check dams in sediment retaining and silting and proves its important role in the water and soil loess of northern Shaanxi.Check dams of northern Shaanxi play significant economic, social and ecological benefits in the sediment retaining, flood prevention, increase in grain yields and improvement of regional ecological environment. The task of returning farmland to forests and pastures is very difficult, so for the change of current situation in order to adjust land utilization reasonably, we should develop basic farmland with great exertion, but terrace and directive cropland are not be extended because of the relief limitation of greater gully density and more lithoid hill, which make check dams construction a decisive role in the small watershed planning.Results by the analytic hierarchy process method showed that the weight sum of improving agriculture disaster resistant, increasing cover degree of forest and grass and increasing perennial drainage was 0.3394, and three indexes of ecological benefits had significant effects on the check dams in northern Shaanxi, so in future ecological development should be focused on with the social, economic and ecological development as the centre task, and secondly construction quality of check dams should be paid attention to, and thirdly check dams and other water and soil conservation constructions should be allocated reasonably.