Space Allocation Measures Of Soil And Water Conservation Measures In The Puwa Small Watershed Of Mountainous Area In Beijing Based On Ecological Security

Beijing mountain area where has abundant resources is an important ecological barrier to protect the capital city, therefore, the protection and restoration must be placed in a prominent position in the control of soil erosion. The scientific allocation of soil and water conservation measures is the basis and premise of the comprehensive prevention and control of soil and water loss. Applying new technologies and means of mathematical methods has become an important means of scientific rational allocation of water and soil conservation measures.This paper presents a method for the allocation of soil and water conservation measures in small watershed of Beijing mountain area, which is based on the ecological security. According to the evaluation results of the ecological safety,the spatial orientation of the various measures implemented in the land. Finally, the planning scheme of water and soil conservation measures in small watershed is drawn up, and the results are analyzed and adjusted. Using ArcGIS10.2 software to analyze the status of soil and water loss in the small watershed of Puwa, and provide the basis for decision making. Making use of hydrology analysis module to divide the river and sub-basin.which is an important basis for the calculation of small watershed runoff resources and conservation measures configuration. Through the ecological safety and natural conditions to establish a small watershed management zoning map, while the principle of spatial optimization of soil and water conservation measures is proposed. The results of small watershed division and land suitability evaluation are regarded as the constraint conditions and the benefit of the reduction of runoff, and sediment reduction under the different measures of rainfall intensity as the decision condition, to obtain the optimal allocation of measures and optimize the configuration process of water conservation measures in quantity, space, time, gradually form a small watershed governance theory.Results showed:(1) In the land suitable for fanning of small watershed, moderate or above accounted for only 5.48% of the watershed area, the basin of basic farmland utilization has certain limitations; highly suitable land accounts for 12.53% of the total basin area, and moderate area accounts for 33.71%, It is possible to create water conservation forests vigorously in the basin; moderate herd accounts for more than 80%, land suitable for afforestation should be adapted to local conditions to actively develop as the Pastoral Land, but also to take active steps to promote natural grassland have been banned good natural recovery, at the same time take active measures to promote natural grassland get favorable natural recovery.(2) Small watershed ecological security evaluation results are divided into five level, security, relatively safe, general, relatively dangerous, dangerous. Their area proportion are 0.05%,22.72%,62.31%,14.83%,0.11%. General safety area is the largest, accounting for more than half. (3) Under heavy rain of the small watershed the runoff and sediment yield is relatively larger, in the located on the upstream and larger catchment areas of sub-basin, the largest runoff cumulative contribution rate areNo.5, No.3 and No.14, their contribution rates were 13.06%,9.94%,11.46%, water outlet of the watershed is 65627.46m3; the average erosion modulus of Puwa small watershed is 502.9 It /km, No.l 1 and No.l sub-watershed have the biggest soil erosion modulus, the modulus are 738.03 t/km2,2 and 713.10t/km2, it shows that the precipitation intensity of heavy rain is extremely important to the separation and destruction of soil in small watershed. (4) The soil erosion modulus of different ecological security levels had significant differences, especially in the area with the lowest ecological security level. (5) In the two plans which be selected by entering the configuration space and water conservation measures, the plan one is better compare to the water and sediment reduction benefits. From the point of view the benefits of water reduction,water outlet of the watershed is 51213.06m", 56344.68m3; from the point of view of sediment reduction benefits,the difference between No.10, No. 13, No.15 is obvious while the rest are similar, it indicating that the proportion of the configuration of forest and grass have a certain influence to Soil and water loss. Through the comprehensive allocation of soil and water conservation measures, the degree of soil and water loss can be reduced to a great extent, and the proportion of different measures to the soil and water loss has a great impact. Which kind of measures can make the whole ecological condition to be optimized for a particular plot, it needs to change the plan until the optimal solution is obtained.