Study On Distribution Of Water And Sediment In Border Irrigation Of Zuncun Yellow River Irrigation District

The sediments in water have a great influence on Yellow River irrigation.Thus silt distribution and treatment in the field has been a big issue for the water-saving irrigation in Yellow River irrigation areas.In order to explore the water and silt distribution and interrelationship in the field,and the quality of border irrigation and the best border check specifications in Zuncun Yellow River district,an field experiment was conducted in Zuncun Yellow River irrigation district from May 2015 to December 2016.The experimental site is located in Yuncheng,Shanxi Province,China(110~o50'E,35~o03'N).Border irrigation is the main irrigation method in the local area,and it was applied in the test field.We had set two borders in the experiment to search distribution of the water and silt.The width of the border is1.8m and 2.7m,respectively,and the length of the border is 300m,and the mean slope of each border is0.1%.The unit-width discharge is 9.26L/(s·m),and the field water capacity is 21%(soil moisture content by mass).There are 9 borders have been set to research better check specifications in Zuncun Yellow River district.In this experiment,we aim to explore:1)border irrigation advancement process and distribution of silt in the sediment-laden flow;2)distribution of soil moisture in the field;3)deposited silt distribution along border lengthwise after irrigation;4)irrigation efficiency and irrigation uniformity in Zuncun Yellow River district.The test procedure are as follows:1)measure the volumetric soil moisture 24 hours before and after irrigation,2)record the water movement and regression in each border,3)collect water samples and measure sediment concentration,4)calculate the sediment-carrying capacity in the sediment-laden flow,5)analyze the variation trend of the sediment content in irrigation water,and 6)study the deposited sediment distribution along the border lengthwise after irrigation;7)simulated the irrigation performance with WinSRFR4.1 software.The experimental apparatus include Parshall flume,ultrasonic flowmeter,time domain reflectometry,laser particle size analyzer,et al.Results showed that:1)the sediments in Yellow River can reduce the capacity of infiltration and make moisture distribution even;2)as a result of this method of irrigation water to promote faster,soil porosity will automatically turn off,at the soil surface to form a closed layer,deep leakage is greatly reduced;3)the sediments concentration decrease by 81%from 0m to 240m,and the sediments half-content diameter and the average particle size lessening gradually with water flow advancing in the field;4)the maximum sediment-carrying capacity of the flow is 0.005kg/m3 on the experimental irrigation condition,which is far less than the sediments content in irrigation water;5)the study of those properties indicates that the bigger the diameter of sediment particle is,the sooner it deposit;6)the deposit sediment consisted of clay(<0.002mm),silt(0.002-0.02mm)and sand(0.02-2mm),and the major composition of the deposited sediment is silt,its proportion is as high as 70%content of sediments;7)the irrigation efficiency and irrigation uniformity cannot satisfied the requirement of water saving,the shortage of irrigation and the excessive irrigation was common in the Yellow River district.It is also found that the deposited mud's sediment gradation of the field's front end is close to the back end,which demonstrates that the silt could be transported to the end of the border.We conclude that water infiltration and drainage reduce the water flow rate,and then hydraulic loss decrease sediment-carrying capacity of the flow.Then the suspended sediment particles in the sediment-laden flow settle down by gravity,and the deposited sediments form a layer which decreases the infiltration ratio on the front end.So the volumetric soil moisture of the front end with longer opportunity time is not bigger than the back end in the border.On the other hand,the paper produce with new border dimensions to improve the quality of irrigation,as follows:the width is 2 meters,the length is 280-340 meters;the width is 3meters,the length is 240-270 meters;the width is 4 meters,the length is 170-240 meters;the width is 5meters the length is 130-170 meters;the width is 6 meters,the length is 110-140 metersThis paper has done plenty of work in studying distribution of water and silt in the field under Yellow River border irrigation.It offers technical support for the distribution of sediments in the field under border irrigation,and it is a reference for water-saving irrigation in Yellow-river irrigation area.It is estimated that,in a long run,the soil texture will change under the Yellow River border irrigation.And the variation tendency is same,either in the front or at the end of the strip.However,the experimental data we collected is limited,the assumption cannot be proved by now.The mechanism of how silt impacts on the soil remains to be investigated.