| The water-wind erosion crisscross region of north Loess Plateau, where the ecological environment is fragile, the ability of soil erosion resistance is weak, its special nature of bess and terrain, semi-dry climates together with the influence of long term farming have made the region become one of the most serious regions of soil erosion in the word. Severe soil erosion not only caused the loss and waste of the water and soil resources in the region, but also made the increasingly severe problem of shortage of water resources become the bottleneck for the ecological environment construction and economic development. Therefore, it is imperative to explore effective measures to control the soil erosion, to solve the problem of water resources and to thoroughly improve the ecological environment in Loess area. Surface runoff process is an important link of water cycle in water-erosion area, as well as is the direct impetus to drive many surface processes in the basin, surface runoff and soil erosion often occur at the same time and interaction, they also have very close ties. Thus, studying the surface runoff problem of water-wind erosion region in north Loess Plateau, such as the forming process, spatial distribution and the dynamic changes in time of surface runoff and so on, can provide the basic hydrological data not only for the forecast of soil erosion and comprehensive control, but also for the accurate evaluation of water resources and the sustainable use of water resources, which is significant to solve region living water and agricultural water.Combined with the National Natural Science Fund Project "Study on Spatial-Temporal Variation Feature and Interaction Effect of Water and Heat of Snowcover-Farmland Combined System"(NO.51279031) and "Development and Application of Numerical Model for Rainfall-runoff of a Distributive Basin Combined with Snowelt"(NO.41271046), the Liudaogou drainage basin in north Loess Plateau is taken as the study area, a numerical calculation model, which is suitable for the typical watershed of gully terrain in water-wind erosion crisscross region in north Loess Plateau, was established combined with GIS technology based on the kinematic wave theory fundamental equations; the applicability of the model was verified by the numerical simulation of the rainfall-runoff process in study area; the model was successfully applied to realize the calculation of long term rainfall-runoff process in study area, the characteristics of runoff in the gully region in Loess Plateau were revealed and the annual runoff coefficient was calculated through a comprehensive analysis on the numerical results. The research results can provide an accurate calculation method and accurate basic data for accurate evaluation of water resources of the gully region in north Loess Plateau.The main research contents and results are as follows:(1) Research on rainfall-runoff process of the watershed. To seek the way runoff occurs and the necessary condition of runoff generation under the condition of different rainfall intensity and soil condition in Liudaogou drainage basin, through a comprehensive analysis of the selected typical rainfall-runoff events; the relationship between the main factors of rainfall and runoff coefficient. The results showed that:among the three rainfall factors, rainfall duration, amount, average rainfall intensity, the effect of rainfall intensity on runoff coefficient is the most obvious, which is view as the main factor and is positively related to runoff coefficient; there were no correlation between rainfall duration, amount and runoff coefficient, but a slight inverse proportion.(2) Study on the reaction characteristics of precipitation of gully terrain in study area. The reaction characteristics of precipitation of gully terrain in study area were revealed through the analysis of synchronous observation rainfall data at the top and bottom of a typical big ditch in study area. The results showed that:there is a difference between the amount and intensity of rainfall in the same period; the maximum difference of single rainfall at the top and bottom of gully was up to39.2mm, the mean difference of a single rainfall is7.5mm, the fluctuation of rainfall value and rainfall intensity at different intervals at the top of gully was larger than that of the bottom, the two series has a higher positive correlation.(3) Establishment and verification of the distributive basin rainfall-runoff numerical calculation model. A numerical calculation model was established based on the kinematic wave theory fundamental equations combined with GIS technology, which was applied to simulate and calculate the rainfall-runoff processes in five years(2005-2009)in study area, on the basis of testing the applicability, the runoff amount and coefficient of each calculation year(2005-2009) were worked out, the mean runoff coefficient among the five years is0.11, and the runoff coefficient in the region where study area located was approximately0.10-0.15. |
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