Simulation Of Soil And Water Loss Process At Regional Scale Based On GIS

Studying the dynamic process of soil and water loss at regional scale was of great importance to understanding the effects of soil erosion on environmental factors and the relationship between global change and regional soil erosion. Meanwhile, it could provide the basis for governmental planning and decision-making in soil and water conservation. This study made improvement for Regional Soil and Water Loss Model, explored the estimation methods of soil moisture and developed a computer module system under ArcGIS environment and .NET Framework2.0, using C# programming language based on theory analysis of soil erosion process and its influence factors. The result was applied in watersheds and regional soil and water loess process was modeled. The results were as follows:(1) Explored the estimation methods of regional soil water content. Considering the climatic factors (temperature), soil factors (soil bulk density), vegetation factor(land use)and terrain factor(topographic wetness index, slope aspect), the water moisture was simulated based on GIS, and the regression results were significant. By comparison, the average error between simulated value and the surveyed value was 0.105, which means the simulation accuracy was high. The result showed that the soil moisture could be modeled based on surveyed soil moisture data considering topographic wetness index, slope aspect, land use, rainfall, and temperature and soil bulk density. Modeled soil moisture could be used in estimation of runoff in Regional Soil and Water Loss Model as antecedent soil moisture. (2) Algorithm design of Regional Soil and Water Loss Model was improved. This research considered antecedent soil moisture, evaporation, raindrop detachment , soil cohesion and different runoff producing mechanisms et al , improved algorithms of the rainfall-runoff process and the soil erosion and sediment yield process in regional soil and water loss. Supported by GIS and computer model system, the process of runoff, sediment, and accumulation were completed.(3) Completed the simulation of regional soil and water loss process in research areas. The model was tested based on data in Jihe River demonstration zone in July 2005 by using different resolution and time step. The results showed that all of the modules designed can function well. The output maps could characterize the soil erosion in Jihe River demonstration zone properly; the spatial pattern and structure depicted by the map were accordant with the practical situation. The soil erosion in Jihe River was mainly influenced by land using and climatic factors at macro scale, and by terrain microrelief at micro scale. The model was applied in Jihe River demonstration zone. The calculated results of the total runoff and sediment were 6.73 billion m~3 and 6.74×10~6 t , and the modulus of runoff and modulus of erosion were 9.48×104m3/km~2.a and 2978t/km~2.a respectively in Jihe River demonstration zone. The simulation results were comparatively accordant with the practical situation.