The Swat Model In Baoji Gorge Irrigation District Of The Improvement And Application

In recent years, with the rapid development of social economy, the water consumption increased rapidly in Baoji Gorge Irrigation District. Together with the decrease of rainfall amount in Weihe River and the water resources management fell behind, the water resource suffered a dramatically shortage in irrigation area. It not only severely restricts district sustainable development of society and economy in the irrigation area, but also makes a serious threat to water resources security, food security and ecological safety.However, at present the water resources management means still in the backward and the modern information management which take information technology as a symbol is basically in blank. Therefore, facing the growing large scale irrigation water shortage problem in semiarid region, based on the computer, GIS and RS such advanced technology, introducing an advanced international model of SWAT, constructing the SWAT model suitable for irrigation area, and applied to the irrigation water resources management, the management for irrigation water is provided with efficient management means and technical support, which has important theoretical and practical significance.This paper choose the United States Department of agriculture development of the SWAT model, with1980,1985,1990,1995,2000,2005,2010of1:100000land use data,1:500000soil types of data,1:50000DEM, canal and daily meteorological and hydrological data as input data. In the semi arid plain irrigation area in Baoji Gorge Irrigation District, the SWAT model must be done some modifications through the parameter calibration and validation. The modified SWAT model could accorde with SWAT simulation requirements. At the same time, the SWAT model of implantation of Baoji Gorge Irrigation District Information Grid GIS system. After implantation of the SWAT model is open, easy to upgrade model modification.The specific work is as follows.(1) The research area is a completely artificial canal irrigation region in semi arid plain irrigation area, irrigation water are distributed in the irrigation area edge. And the irrigation can only rely on artificial ditch and canal, while DEM automatically extracted from the stream to the plain irrigation area is on little significance. In this paper, using artificial canal network instead of natural water systems, combined with land use, soil type, DEM, irrigation farmland system data to SWAT spatial discretization principle, the irrigation region is spatially discretizated through the superposition analysis. And SWAT is flit in the blank of completely artificial ditch irrigation plain irrigation application. Add, Baoji Gorge Irrigation District of Shaanxi province is the largest in the nine irrigation area. The irrigation is mainly in farmland with the gross area of approximately3831.3square kilometers. The HRU is first divided into farmland and non-farmland in two parts, in farmland directly calculates the leakage, in non-farmland calculates runoff, then finish the calculation of leakage, evaporation, Improved water transport modeling accuracy in the farm part of irrigation area(2) In the SWAT model, the actual evapotranspiration of plants is determined by the potential evapotranspiration and leaf area index through operation function. Models of leaf area index for American crops in default are not suitable for Chinese. And more unsuitable for semi arid water-deficient irrigation plain of the actual crop evapotranspiration calculation. This paper uses SWAT model in the actual evapotranspiration calculation program change is commonly used for domestic crop coefficient method to calculate actual evapotranspiration of crops. And that lead to the SWAT model in China become more scientific in application and more accurate in simulation.(3) The improved SWAT model adds the capillary water upward and the main channel leakage loss to groundwater depth value in the calculation. As the variable lack of measured data, the model makes an increase of this module. The groundwater module in the original SWAT model is used to calculate the parameters of groundwater level without involving the groundwater depth value. While in the irrigation and water conservancy, many aspects are related to groundwater. This article takes irrigation on groundwater calculation integrated in the model, increases groundwater depth calculation, namely in groundwater and related calculation, considers the groundwater reserves, so as to estimate the groundwater reservoir capacity more accurately in calculating the surface evaporation.(4) The SWAT model of capillary water upward calculation changes to Mao Chi, Neitsch SL2002calculate method, because the algorithm in the model does not consider the capillary rise of water on Soil and crop effects. While Baoji Gorge Irrigation District located in the semi-arid area with soil in the unsaturated state is a kind of consideration on the capillary effect of Soil and crops calculation method. The new model can more accurately reflect the supply of the capillary rise on soil water, especially meaningful to Baoji Gorge Irrigation Area which is a semi-arid irrigation plain.(5) As a result of Baoji gorge irrigation transmission is completely relying on ditches and drainage, Considerring the canal seepage loss is very necessary. The SWAT model of drain leakage recharge is mainly confined on the calculation for natural river basin, and is not suitable for the artificial Ditch irrigation. However, the Baoji Gorge Irrigation District is located in the south part of Loess Plateau, the groundwater level is low. The limited runoff in surface is recharging the confined water through the phreatic aquifer very difficultly. Here in this article the improvement is more suitable for the requirements of the simulation in semi arid irrigated district.The conclusions of this paper are as follows.(1) Through the improved model and the calibration of1996-2005based data in Baoji Gorge Irrigation District, the SWAT model simulates the basic requirements (error less than the measured value20%). The validation results on2000-2010based data shows that the improved error is less than15%. The improved model is successful.(2) This paper establishes in Baoji Gorge Irrigation area a Grid GIS system with reference to American scientist Ian Foster. It puts forward three basic requirements in grid computing. The system database is designed in detail and strictly matches national foundation data of annotation-standardization, standardization. It changes circumstance of the data standard inconsistent and data production non-standard, avoids problems of system operation caused by the data difficulties. At the same time, This paper takes an open model library into the database, which can be more accuratly simulate the irrigation water resource status, and can avoid unnecessary waste according to the demand of water. At the same time, open modeling and more variable model improvement with new model integration or replacement can greatly reduce the management cost and unnecessary loss of resources.