| The northwest region of China has abundant land resources and abundant light and heat resources,but the lack of precipitation and water resources has a great impact on the sustainable development of regional economy.Therefore,people develop irrigation areas through water diversion projects to meet the demand for water resources.The development of water diversion projects brings great economic benefits and also improves the ecological environment of the region.Water and salt migration,accumulation of restructuring and,with a large area of soil salinization,and make the appropriate tillage land farming,soil salinization has become an important factor restricting the development of local agriculture,therefore explore the irrigation area of water and salt movement change rule for the management of land salinization and land reclamation is of great significance,while irrigation area to prevent environment due to water and salt movement and development of soil environmental catastrophe,change the previous extensive irrigation water mode,should adjust the structure of water,change the irrigation mode,improve the efficiency of agricultural water,at the same time rely on supporting engineering to adjust the irrigation mode and eliminate the secondary salinization land,Comprehensive control measures have a positive effect on the control of soil salinization in irrigated areas.Soil moisture and salinity in irrigated areas are in a changing process under the influence of natural conditions and human factors,and their characteristics are different in different periods.In this paper,3S technology was used to study the spatial-temporal differentiation characteristics of soil moisture and salinity in irrigated areas.On the basis of traditional remote sensing interpretation,spectral characteristics of saline soil in Landsat data were differentiated to extract information of severe,moderate and mild saline and alkaline lands in the irrigated area,and the accuracy was tested.The spatial analysis tool of ArcGIS software was used for spatial interpolation of soil salinity in typical areas,and the interpolation results were compared with the inversion results.Combined with remote sensing data and geographic information system data,the risk assessment factors of soil salinization were determined,and the grey assessment model of soil salinization risk in jingdiangru area was established.At last,the driving force of soil salinization in jingdian irrigation area is analyzed from natural and human factors,and some Suggestions on improving soil salinization in irrigation area are put forward in terms of economic management policy and ecological engineering technology measures.This topic by the national natural science foundation of the pumping irrigation area drought salt and water movement(scene electric irrigation area),the influence on the regional soil and water environment research(51279064),the dry desert of field irrigation on the regional scale research on the influence of soil water and salt differentiation process(51579102),the typical structure of desert plant drought-resistance in hexi corridor and its spectrum characteristic research(31360204)jointly funded project,to carry out the scene electric irrigation area of soil water and salt in time and space differentiation characteristics research,the main result of paper conclusion is as follows:(1)Set penalty factor C value between 20~100,the smallest nuclear parameter sigma min set to any two of the training sample average distance,initial nuclear parameter sigma ini nuclear parameter is set to the minimum of 10~15 times,nuclear parameter sigma step step length can be set up for 1~3,accuracy assessment by building the confusion matrix,the classification accuracy is over 75%,the Kappa coefficient at around 0.75,meet the accuracy requirement of saline-alkali land recognition(2)Selected scene first phase of electric irrigation irrigation area as the experimental zone,selects 1994,2001,2008 and 2015,the salt data of 0~100 cm,respectively,using the distance function method,trend surface method and spline function method,different interpolation methods,such as interpolation experiment was carried out,from the interpolation result total interpolation precision inverse distance weighting method(power.3)the highest(76.00%),followed by ordinary kriging method trigonometric function(69.00%),inverse distance weighting method(1)power the lowest(56.00%),The inverse distance weight method was used to carry out spatial interpolation analysis of the controlled elements of salinization of the closed hydrogeological unit in the irrigated area.According to the interpolation results,the overall content of soil salinity in the region was relatively high,with the highest salinity in the middle region and the highest salinity up to 8.49%.In the middle and upper regions,the surface soil conductivity was large,and the difference between the north and south was large,reaching a maximum of 2.03(S/m).In the embedded depth of groundwater is characterized by the upper shallow depth,the eastern and northern edge of groundwater depth is deeper,overflow surface,area of shallow groundwater depth in 1.32~3.31 m,concentration in the groundwater salinity is characterized by moderate and part is larger,between 6.03~7.02(g/l),the rest of the region mineralization concentration is relatively low and the change in small,distribution between 2.15~4.36(g/l).(3)Combined with remote sensing data,spatial data and field data,by constructing the database,the evaluation factor,the different types of data remote sensing inversion or space interpolation,to generate the raster layer set,and by adopting the combination of subjective and objective method to determine weight coefficients of each evaluation factor,construct the salinization risk grey evaluation model for comprehensive evaluation.The risk of soil salinization in the study area was quantitatively evaluated and analyzed.The area with a risk level of 3 is the area with"general risk",accounting for 43.16%of the total area,about32.45km~2,and the range of risk value is between 0.1 and 0.3.The level 2 risk area accounts for18.88%of the total area and the area is 14.20km~2,which is the transition area between level 1risk and level 3 risk.Overall,area salinization risk rating to"risk"and"high risk"is given priority to,within the region of soil salt content is higher,salinization is relatively serious,"general risk"and"high risk"accounted for 64.78%of total area,to"high risk"areas should focus on measures to governance,further development control salinization,for"general risk"area should be effective preventive measures to prevent its further development,the evaluation results for soil salinization prevention and provides the theory basis for effective utilization of agricultural water and soil resources. |
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