| As the most common irrigation technology for surface irrigation,the low quality of border irrigation is still the main problem.In order to solve this problem,this paper selected Hetao Irrigation Area as a typical research area,analyzed the spatial variation law of soil physical properties,estimated soil infiltration parameters according to soil transfer function and numerical simulation method,and obtained the slope data at different locations using remote sensing image data,and finally put forward a reasonable border irrigation system layout model in Hetao Irrigation Area.The following conclusions are drawn:(1)The spatial variability of soil physical and chemical parameters such as soil particle and organic matter content in Hetao Irrigation Area was analyzed.The results showed that the content of clay,silt and sand changed slightly with depth,soil water content increased gradually from top to bottom,soil bulk density changed slightly with depth,and soil conductivity decreased with the increase of soil depth.The spatial distribution pattern showed that the sand content of soil on both sides of Hetao Irrigation Area was higher,and the clay content,silt content,soil moisture content and soil conductivity in the middle of the irrigation area were higher.The volume fraction of soil in Hetao Irrigation Area was evenly distributed with no significant difference.(2)Using RETC software to estimate hydraulic characteristic parameters,and combininrg with numerical simulation method,the Kostiakov formula infiltration parameters at different locations in the irrigation area were obtained and their spatial variation characteristics were analyzed.The results showed that there was no significant difference in the Kostiakov formula infiltration parameters(k,a)between two layers(0-20 cm and 20-40 cm)and three layers(0-20 cm,20-40 cm and less than 40 cm).The range of infiltration parameters k ranged fron 27.39 mm/ha to 148.84 mm/ha,and the infiltration index a ranged from 0.31 to 0.65.The reference infiltration coefficient K and infiltration index a ranged from 44.31 mm/ha to 78.98 mm/ha.From 0.30 to 0.55,it shows that the infiltration parameters obtained by fitting are reliable,and the spatial distribution law shows that the infiltration parameters K and infiltration index a on both sides of the irrigation area are larger,while the infiltration index a in the middle is smaller.(3)A method for obtaining the slope of field on the scale of irrigation area is proposed and verified.The results show that the maximum relative error,the minimum value and the average relative error of the field slope obtained by the proposed method are 36.20%,7.90%and 16.16 respectively,and the maximum relative error,the minimum relative error and the average value of the field slope measured by the reference are 16.49%,5.75%and 11.73%respectively,respectively,on both sides of the 1:1 straight line in Hetao Irrigation Area.It shows that the simulated and measured values of field slope have good consistency.Considering the actual situation of irrigation area,the proposed method is believed to be reliable.(4)WinSRFR software was used to simulate the quality of border irrigation water under different soil texture,field slope,border length and single width discharge conditions in Hetao Irrigation Area.With irrigation efficiency Ea and irrigation uniformity Du greater than 0.85 as constraints,two optimal layout models of border irrigation specifications were proposed:model(l):under the condition of average inflow flow of about 0.025m3/s,the existing length of border irrigation field was kept unchanged at 50m.The width of the border is reduced to 6-8 m,and for the area with slope greater than l,the laser leveling method should be used to reduce the slope to less than l.Mode(2):For areas where it is relatively difficult to use laser leveling technology,when the slope of the field exceeds l,the length direction of the border field can be merged.For silty clayey loam,when the slope is 2 and 3 the length and width of the combined border are 100 m and 15-25m,respectively;when the slope is 4 and 5 the length and width of the combined border are 150m and 17～25m respectively.For silty clay,when the slope of the field exceeds l,the combined border length is 150 m and the width is 17～25m.For silty loam,when the slope of the field exceeds l,the combined border length is 150 m and the width is 18-25m.Because the border width increases after the combination of border fields,in order to ensure that border irrigation belongs to one-dimensional flow movement,an outlet is set at about 10 meters each. |
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