Characterization Model Of Cumulative Infiltration And Wetting Front Migration Distance In Furrow Irrigation

In order to further simplify the prediction model of the cumulative infiltration volume and the moving distance of the wetting front of furrow irrigation,and try to improve furrow irrigation technology.Based on soil hydrodynamics,this paper selects homogeneous soil furrow irrigation and sand-layered furrow irrigation as the research objects,which uses HYDRUS-2D to simulate and analyze the effects of different influencing factors on soil water infiltration characteristics and wet body characteristics under two furrow irrigation conditions.Seeking for the domi nant factors affecting furrow irrigation in homogeneous soil.A simplified prediction model for cumulative infiltration and wetting front migration distance is proposed.In addition,the effects of different factors on furrow irrigation in sand-layered were analyzed.The following main research results are obtained :(1)Based on the theory of unsaturated soil water infiltration,the mathematical models of soil water movement for furrow irrigation in homogeneous soil and furrow irrigation in a sand-layered was established,which were solved by HYDRUS-2D,and the data of cumulative infiltration and wetting front migration distance under two conditions were selected for verification.The results show that the MAE and RMSE of the measured and simulated values are close to 0,PBIAS≤±10%,NSE ≥ 0.938,Which proves that the HYDRUS-2D can be used to simulate the water movement of furrow irrigation in homogeneous soil and sand-layered soil,and the built model and solution method are reliable.(2)Through analysis,it is concluded that fo r homogeneous soil furrow irrigation,the cumulative infiltration is mainly affected by the type of soil,depth of irrigation water,width of furrow bottom,and the slope foot of furrow irrigation.The initial water content and furrow depth have little eff ect on the cumulative infiltration.Established the relationship between the depth of irrigation water,the width of furrow bottom and the slope foot of furrow irrigation with the irrigation wetted perimeter(r=B+h/sinβ),which proposed a simplified prediction model for the cumulative infiltration of furrow irrigation in homogeneous soil and with only one parameter.Through comparative analysis with the literature model,the result is that the simplified prediction model is more accurate.(3)For homogeneous soil furrow irrigation,the wetting front migration distance is mainly affected by soil texture,irrigation water depth and wetted perimeter.The initial moisture content is less affected.The wetting front migration distance in the three directions and the irrigation time are equal.A simplified prediction model for the migration distance of the wetting front of furrow irrigation with different soil textures is established.The predicted value of the model is in good agreement with the measured value of the experiment.The only unknown parameter of the built prediction model is Saturated hydraulic conductivity,which is simple to calculate.(4)Using HYDRUS-2D,the cumulative infiltration and wetting front migration distance of furrow irrigation with sand l ayer under different influence factors were simulated and analyzed.The cumulative infiltration amount was mainly affected by the width of furrow bottom and irrigation water depth,the texture of sand layer had little influence,the horizontal migration di stance of wetting front was mainly affected by irrigation water depth,and the vertical migration distance was affected by both irrigation water depth and sand layer texture,The texture of sand layer has a significant influence.(5)The simulation compared the water infiltration characteristics of mean soil and sand layer furrow irrigation.The results show that under certain initial conditions,the cumulative infiltration of the two is almost the same,indicating that the sand layer has little effect on the cumulative infiltration volume.The two wet fronts are removed from the vertical downward direction,and the other directions are basically the same.After the vertical downward wet front enters the sand layer,the infiltration rate is relatively slow,but after a certain period of time,the infiltration rate will be within a short period of time.The phenomenon of speeding up indicates that the sand layer has blocked the movement of soil water to infiltrate downward for a certain period of time.