Study On Soil Water Transport Characteristics Of Pipe Irrigation

In view of the problems of low water use efficiency and poor distribution uniformity of border irrigation,combines with irrigation actuality in the North China Plain,this paper proposes pipe irrigation technology.This technology is a new type of ground water-saving irrigation technology in which pipe is arranged in the middle of border check and water is transported by pipe.In order to explore soil water transport characteristics under pipe irrigation,through the combination of theoretical research,indoor tests and numerical simulations to carry out pipe irrigation infilation characterristics of exprimental research,analyzed the effect of different initial soil water content,soil bulk density,irrigation quota and border width on the characteristics of soil moisture migration under pipe irrigation,the main research results were as follows:(1)Under the conditions of initial water content,soil bulk density,irrigation quota and border width,there was a exponential relationship between field surface water depth and infiltration time.As the same infiltration time,the surface water depth of pipe irrigation increased with the increase of soil initial water content,soil bulk density and irrigation quota,but the border width had no significant effect.A mathematical model was established with the water depth as the dependent variable,influencing factors and infiltration time as the independent variables,and after verification,the model was high reliability.(2)Under the conditions of initial soil water content,soil bulk density,irrigation quota and border width,the shape of wetting body was approximately rectangular inside the ridge and 1/4 oval outside the ridge.Under the same infiltration time,the ratio of vertical and horizontal wetting front migration distance increased with the increase of initial soil water content and irrigation quota,and decreased with the increase of soil bulk density,but was not significantly affected by border width.With the increase of initial soil water content,irrigation quota and border width,the soil bulk density decreased,the area of wetted body was gradually increased.(3)Under the condition of soil initial water content,soil bulk density,irrigation quota,and border width,wetting front migration distance and the infiltration time had a good logarithmic function relationship;A mathematical model was established by taking the wetting front migration distance as the dependent variable,the soil initial water content,soil bulk density,irrigation quota and infiltration time as the dependent variables,and the model could better reflect the process of the wetting front;The relationship between the migration speed of wetting front and infiltration time is power function;Under the same infiltration time,the migration distance and speed of the wetting front increased with the increase of the initial soil moisture content and irrigation quota,and the decrease of soil bulk density showed an increasing trend,but the border width had no significant effect(4)The comprehensive prediction model were established for surface water depth and wetting front migration distance,Including the parameters of soil initial water content,soil bulk density and irrigation water quota.After comparing the predicted and measured data,it found that comprehensive prediction model had better prediction precision.(5)Under the conditions of various influencing factors,the soil water content contours were distributed from sparse to dense with the depth of the soil layer,the soil surface water contours were sparse,the soil water content was high,and the water content near the wetting front changed greatly,the water content contours were dense.At the same infiltration time,the larger the initial water content,soil bulk density and irrigation quota,the larger the area of wetted body and higher water content,and the larger the water content of the same soil depth.However,the border width had no significant effect on the distribution of water in wetted body.(6)Using HYDRUS-2D software to numerically simulate soil water movement in pipe irrigation,the results showed that the simulated values of the wetting front and soil water content were in good agreement with the measured values,so the model built using HYDRUS-2D could better simulate the process of soil water movement in pipe irrigation.