Process Research Of Water And Salt Spatial Differentiation Based On ArcGIS In Jingtaichuan Yellow River Pumping-Irrigation Area

The natural environment problems of globalization are becoming more and more serious,and the proportion of soil and water environment problems is the most.In extreme arid area,the secondary salinization of arable land has become an important problem affecting the sustainable development of irrigation area.The fundamental reason for the evolution of soil and water conditions into disasters is the differentiation of moisture and salinity transport in the soil.In order to clarify the movement state and differentiation characteristics of soil water and salt movement,we must first find out the movement process of soil water and salt.This will lead to better control in the development process.And eventually the soil moisture and salt will move to our desired direction.Soil moisture and salinity in irrigation area are both a spatialized regional variable,and they have necessary connections and differential variability in a certain space.It is the combination of connection and variability that determines that the spatial migration of water and salinity differences is difficult to identify.In the study,the data base of saline alkali land in typical irrigated area is obtained through field investigation and remote sensing interpretation.The problem is solved by using remote sensing interpretation and spatial interpolation method and evaluating the result of spatial interpolation with error matrix.The spatio-temporal differentiation of scale soil water and salinity in the region of irrigation area is the final result of combination and cooperation of many factors.In this paper,we use the grid superposition method to combine many factors,and find out the overall process of water and salinity in spatio-temporal differentiation.In the process of superposition,the dimension of each factor is eliminated by using reclassification,so that the result of superposition is of practical significance.Superimposition weighting factor is calculated by the method of expanded analytic hierarchy process.The research is based on the National Natural Science Foundation of China(51279064),the study on the effect of field irrigation on the regional soil water salinity in the arid desert area(51579102)and the typical desert plants in the Hexi Corridor The study on the drought resistance structure and its spectral characteristics(31360204).The main results of the study are as follows:(1)The maximum likelihood classification method is used to extract information from remote sensing images of Jing-Dian irrigation area.It shows that the distribution of saline alkali land was more in the eastern part of Jing-Dian irrigation area,and the development of saline alkali land in the irrigation area was accelerated.Among them,the growth rate of mild saline alkali area was the fastest,followed by moderate saline alkali area and severe saline alkali area.(2)By using the spatial interpolation theory and the error matrix,it is found that the inverse distance weighting method(power 3),ordinary Krikin(exponential function),ordinary Krikin(trigonometric function)and ordinary Krikin(spherical function)are the optimal interpolation methods for soil salinity,groundwater salinity,irrigation water and groundwater depth.The optimal spatial interpolation method is used to interpolate the annual data of soil salinity,groundwater salinity,irrigation water and groundwater depth.The distribution and changing process of soil salinity,groundwater salinity,irrigation water and groundwater depth were obtained through the interpolation results.(3)By using the method of expanded analytic hierarchy process,the weights of various factors that affect the field-scale spatio-temporal differentiation process of soil water and salinity are determined.The sequence of the weight of each factor is as follows: the groundwater depth is 0.3190 > the salinity of groundwater is 0.2710 > the soil salinity is 0.1971 > the surface salinity is 0.1748 > the surface irrigation amount is 0.0381.The proportion of groundwater depth and groundwater salinity is up to 59%,which indicates that groundwater has a major role in the change of the field-scale spatio-temporal differentiation process of soil water and salinity.(4)The dimension of each influence factor is eliminated by using reclassification,and the various dimensionless factors are superimposed and integrated by using grid data weight superposition.Superposition diagram indicate that the overall distribution of water and salt in the Jing-Dian irrigation distric is gradually rising from the west to the east,and increasing with a curved line from southwest to northeast.Under the action of irrigation in the irrigation area,water and salt move from the southwest to the northeast.The groundwater depth in the northeastern part of Jing-Dian irrigation distric has increased significantly,and salinized soil has increased greatly.For the serious problem of saline alkali land development in the northeastern part of Jingdian irrigation area,the main reason is that the groundwater depth is relatively shallow and the mineralization degree is relatively high.It is recommended to drain groundwater in this area to reduce groundwater level and irrigate the surface to reduce soil salinity in the tillage layer.