Swap Model Distributed Simulation Of Soil Water And Salt In Hetao Irrigation With Water-saving Irrigation

Hetao is one of the China’s design largest irrigation area in Inner Mongolia, is a typical place no irrigation will be no agriculture. However, in a severe shortage of water resources today, available water resources in China are faced with increasing scarcity of the problem, the water used to irrigation reduces year by year, irrigation soil salinization level increasingly heavier. Therefore, study of soil water and salt space-time evolution, For the development of the Irrigation District irrigation strategies and salt and water regulation and control programs, as well as to ensure the scientific implementation of China’s large-scale Irrigation District works to provide a theoretical and applied foundation. According to these problems, it introduced a new distributed simulation method that combining SWAP model with GIS and RS technology, under the conditions of the shahao, it simulated spatial and temporal evolution of soil water and salt in the regional scale, under the status quo irrigation and water-saving irrigation two conditions, assess the irrigation efficiency, provide the basis for the development of water-saving irrigation methods in the conditions of water scarcity. The main research results were as follows:(1) In this paper using of remote sensing software ENVI4.7with ArcGIS9.3, determine the distribution pattern of the crop planting structure and space in shahao, get the wheat, corn sunflower grow and other crops acreage, crop planting structure was a flower arrangement shaped distribution. The soil type, soil salt type, groundwater depth was studied using spatial interpolation method of Thiessen Polygon, Inverse Distance Weighted, and surface analysis method in ArcGIS9.3. The results showed that: Salinization of soil and re-salinization of soil is only found in northern and central in the study area, and the area is lesser, Most of the rest areas are mainly non-salinization of soil and light salinization of soil. There are nine types of soil with strong spatial variability. The spatial distribution presented flower arrangement appearance. The changes of groundwater lever in year related to the seasons. The depth in crop growth period was lower than other time. In this period, the depth in September was the highest. In the regional scale, the depth and the change range in upper reaches was higher than middle and lower reaches. Hereby, the groundwater lever was divided into seven partitions. The main impact factor space superimposed to generate the345regional soil water flow distributed simulation unit.(2) SWAP model to simulate the distributed simulation unit of soil water and sal; transport, the simulation in the unit of salt and water soil vertical migration dynamic change regulation. The results showed that Crop root zone water flux at the bottom of the study area, soil water storage, soil salt storage showed alternating dynamic variation. Crop root layer and the groundwater water exchange frequently. The dynamic process of the crop root zone soil water storage capacity is mainly affected by irrigation, Evapotranspiration constraints. After irrigation, due to greater irrigation quota, the soil moisture content then reached saturation, crop root zone soil water storage in the sudden increase; As soil evaporation and crop transpiration, soil water is gradually consumed, the crop root zone soil water storage before the next irrigation with crop growth and a gradual decrease. after Irrigation or rainfall. due to the leaching of soil salinity down movement leaving the root zone storage salt then reduce, then with the evaporation and transpiration deplete the soil moisture upward movement driven by soil salinity up before the next irrigation root zone storage salt gradually increased. Root zone reservoir at the end of the simulation period the salt is greater than the root zone storage salt early period, although the root zone storage salt with temporal fluctuations of dynamic change, but the overall root zone was the trend of salt accumulation.(3) The regional soil salt water of the SWAP model of dynamic distributed simulation model, in the status quo irrigation and water-saving irrigation two conditions, through the simulation unit of soil water salt vertical migration by SWAP model simulation, in GIS technology to create a spatial distribution of farmland soil water and salt balance components. The results showed that due to the different soil types, the soil salt, groundwater, crop planting structure types of influence, the study area area at the bottom layer water circulation root crops, root system soil, root layer ChuYanLiang supply, crop potential tengfa quantity and actual crops to the ratio of the transpiration, irrigation water effective utilization rate space uneven distribution, have large differences in the number, has the significant space mutation characteristics. under the same conditions of groundwater depth and crop planting structure and soil type, because of the number of irrigation water in water-saving irrigation conditions less than status quo irrigation conditions, the study area, on the whole, deep seepage reduce and groundwater recharge increase; crop root zone water storage in the study area as a whole tended to decrease; and because the more groundwater recharge and less deep seepage reduce the injector role, salt of the crop root zone storage in the study area as a whole showed an increasing trend; but the actual transpiration and potential crop up the ratio of the hair is also Ta/Tp in about0.9, crop does not significantly decrease also results. In the water-saving irrigation conditions, due to the deep seepage reduced, in the harvest soil water storage to reduce, the irrigation water utilization rate can be increased to100%, improve the amplitude can be as high as72.3%, have a great contributions to saving water. Therefore, from the shahao, in the field of the present situation of irrigation water based on the reduced by10%, by using of the new water saving irrigation system, have no significantly influences to reduce crop yield, which have great potential in the field of the water saving.