Study On The Feasibility Of SWAT Model On Small Scale Basin

Water is the source of life and the basic element of entironment. Soil and water loss and deterioration of environment resulted from congenital natural ecosystem and long-time improper human activities, which badly restrict local social economic sustainable development. Therefore, finding out the rule of soil and water loss, which is significant for setting down measures of management of soil and water loss and local social economic sustainable development.Recently, with the development of the distributed hydrological model, watershed hydrological modeling is more close to real hydrological process. SWAT(Soil and Water Assessment Tool) model is one of the most representative distributed hydrological models, which was developed by USDA-ARS(US Department of Agriculture-Agricultural Research Service) for predicting the impact of land management practices on water, sediment, and agricultural chemical yields in large, complex watersheds with varying soils, landuse, and management conditions over long periods of time. The model is physically based and enables users to study long-time impacts.Hydrological model can model the hydrological process of different spatial scale watershed. Because of lacking of hydrological and meteorological data and variability of underlying surface, the process of middle and large spatial scale watershed is difficultly simulated. On the contrary, small scale watershed could simulate the real process as a result of easily getting the hydrological meteorological data and little variability of underlying surface.In this study, distributed simulation was carried out in the study area of Yinhe Basin, upriver of Huaihe Watershed supported by GIS. The main study of this paper are as follows: parameterization of the model,sensitivity of the parameters,calibration and validation of the model and the application of the model.The main results of this dissertation are as follows:(1) SWAT model is feasible to be applied in small scale basin. Distributed hydrologicalsimulation was carried out in the study area of Yinhe Basin, upriver of Huaihe Watershed. Whose area is 5.73Km , is belong to small scale basin. The total basin was discretizated 23 sub-basins. The result showed that average precision was up to 80%, R2 and Ens (Nash-Sutcliffe) were all up to 0.94. The precision of the simulation was pretty well which proved that the SWAT model is feasible to be applied in small basin.(2) Some of input parameters could be acquired from transformation calculation. SWATmodel is restricted by its lots of input parameters. This paper studied the soil texture conversion and the preprocessing of the weather data. The soil texture conversion was calculated by the statistical software-MatLab. Available water capacity,saturated hydrological conductivity and soil bulk density could be calculated by Saxton software. And preprocessing of weather data was calculated by SWAT model extended software, and they can offer one simple and fast method for model input data.(3) Ascertain the sensitivity parameters of the model. This paper analyzed some sensitivityparameters of the model, the results showed that AWC (Available Water Capacity),CN2 (Curve Number) and ESCO (Soil Evaporation Compensation Factor) were most sensitive parameters. By the means of adjusting these parameters which can be helpful of calibration and validation of the SWAT model.