| Aksu area is in the northwest of China,it is located in the arid and semi-arid area.The contradiction between supply and demand of water resources and soil salinization in the basin have been seriously restricting the regional economic,social and agricultural sustainable development.Therefore,it should optimize the irrigation system on the basis of mastering and understanding the spatial distribution of water and salt in soil in the irrigation area,It has very important practical significance for the rational allocation of water resources and the control of soil salinization in the study area.In this paper,the downstream irrigation area with serious salinization in Aksu Basin is taken as the research area.The study analyzes the spatial distribution characteristics of soil water and salt and the influencing factors of salinization in the irrigation area by statistics,geostatistics and correlation analysis,and it also optimizes the irrigation area by constructing the soil water and salt migration model on the basis of field experiment.The main conclusions are as follows:(1)The soil moisture content and salt content in the study area changed greatly,and the degree of spatial variation was complex.The soil moisture content was susceptible to random factors.The salt content before irrigation was susceptible to structural and random factors,and the salt content after irrigation was more susceptible to random factors;(2)The spatial distribution characteristics of soil water and salt parameters in each layer during the same period have certain similarities and differences,but in general,there is little difference in each parameter.The distribution of water content affected by irrigation is chaotic,and the salt content is generally high in the south and low in the north.Through the analysis of the relationship between soil water and salt,it was found that there was a positive correlation between soil water content and salt content in surface and subsurface layers,and a negative correlation between soil water content and salt content in deep layers;(3)To a certain extent,natural factors and human activities in the study area will cause differences in the speed of water transport in the soil and changes in groundwater level and water quality,The shallower the groundwater level,the greater the salinity,the greater the soil salinity,will have an impact on the spatial distribution characteristics of salinization in the area;(4)The main factor of affect soil salt content is groundwater salinity in each layer of the study area,and the surface elevation is the smallest factor.With the increase of soil depth,the influence of groundwater depth on soil salt content gradually increases.Therefore,in the future,groundwater factors in the control area can be emphatically considered in the salinization control in the region;(5)The field irrigation experiment was carried out in typical areas.It was found that the flood irrigation amount was large,the infiltration amount of irrigation water was also large,and the salt was also more with water.Therefore,it was easy to cause the water content and conductivity of each layer to change greatly.Hydrus-1D was used to construct the numerical model of water and salt migration.After verification and identification,it was found that the measured and simulated results of soil moisture content and conductivity in each layer were well fitted,and the parameters were reliable,which could be used for practical simulation application;(6)Using the model to optimize the spring and winter irrigation water of the main crops in the irrigation area,the optimal spring irrigation water of cotton and corn are 90m~3/acre and 70m~3/acre,and the optimal winter irrigation water of wheat and fruit trees are60m~3/acre and 100m~3/acre.The dynamic change of soil water and salt in the study area is a very complex process.In the future,the optimization design of irrigation system can be further considered according to the actual situation,such as soil texture,irrigation water and water quality. |
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