| This paper is based on the soil and water conservation project named "slope runoff utilization study for the southern district of Shanxi province". The author takes the Spatial optimal allocation of water (slope runoff) and land (slope land) as key research direction and takes the planning of the Spatial optimal allocation of water and land of MaJiaGou small watershed, which is the typical example of small watershed district, as typical case to discuss how to formulate plans for optimal allocation of land, and the supporting plans of utilization of slope runoff and optimal allocation of water storage system. The achievements would give valuable suggestions on the related study and governance on small water sheds for the areas which have the same mountainous areas background in the Southern part of Shanxi province.With the aim at formulating resolution on optimal spatial water and land allocation in small watershed to direct the governance on soil and water conservation, this paper focuses on the optimum of the land utilization and slope runoff utilization in mountainous small watershed.The following results are achieved:1,The author decided the research method by considering the following factors:the previous study work in the project "slope runoff utilization study for the southern district of Shanxi province", and the current study status of optimal water and land allocation, utilization of water storage system of slope runoff and watershed hydrologic model.(1) Construction of linear programming mathematic model is as following:the pattern of slope land planning and utilization as decision variables; economic benefit maximum as target; the quantity of slope runoff and slope land resources in the small watershed as constraints. Calculation program helps to get solution, which includes optimal allocation of land utilization area and the corresponding optimal allocation of catchment area and irrigation area, from simplex method model.(2) The principle and method for the planning of the optimal spatial allocation of land and water are developed and applied to case study area- MaJiaGou small watershed in ShangNan County. ArcGIS software was applied to analyze overlaid terrain map, geomorphologic map, slope map and land-use map. ArcGIS was secondarily developed by C++ language to achieve the optimal spatial allocation plan and land resource evaluation chart for water and land resource in MaJiaGou small watershed.2,Propose to employ ArcGIS9.2 software to extract topographic feature data based on DEM (Digital Terrain Model) and therefore make the statistics data of slope resources in small watershed more efficient and precise.3,DEM of watershed is developed by ArcGIS9.2 software. The built-in Hydrology Model of ArcGIS9.2 is applied to do "fill sinks" treatment to DEM, therefore, threshold is set to divide the sub-watershed and extract water data and river node data. And the above is the critical foundation for calculation of small watershed slope runoff and site selection of water storage system.4,Hydrological model was build and applied based on GIS. Due to its excellent spatial analysis performance, ArcGIS9.2 was applied to overlay the land-use map and sub-watershed map, extract necessary parameters for SCS storage model and set CN value to sub-watershed.SCS model is employed to calculate the runoff producing during dekads according to the land use conditions.5,The impounding period used in calculation of the impoundment engineering volume is subdivided from month to dekad. Results from "cumulative method" and "back sequence method" were compared. Comparison demonstrated that "cumulative method" result which takes the impoundment volume within dekad into consideration, is large than that of "back sequence method". And the above comparison is an innovation provided by this paper.6,Arc Hydro model is applied to attract hydrographic node automatically, and optimize water storage system site selection. And this is another innovation.7,Put forward method for determining single impoundment engineering volume. To water storage system which has definite spatial location, "simulated calculation method" and "allocation of gross storage method" are employed. The compared result indicates that "simulated calculation method" based on SCS model combines well with GIS and has high simulation level while the calculation process is rather complex. The application of "simulated calculation method" in a comparatively larger watershed will give results deserved study and comparison. "Allocation of gross storage method" is suitable for areas which have definite gross storage and the calculation is comparatively simple, while this method needs to be completed when used in conditions of allocating storage by irrigated area ratio and the highest altitude water storage system ratio.The strong point of this paper is the comprehensive consideration of water and land resources as a whole. Optimal spatial allocation of water and land resource and optimal spatial allocation of water storage system ensure the allocation plan to be optimal. There are two levels of allocation in this paper. The primary level is the optimal spatial allocation of water and land resources, and the second is the optimal spatial allocation of water storage system corresponding to the primary optimal spatial allocation of water and land resources. |
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