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# The Study On Mult-factor Mathematical Model Based On Two-Dimensional Infiltration Parameters Of Canal Bed And Calculation Method Of Channel Water Utilization Efficiency

Posted on:2021-02-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:J ZhangFull Text:PDF
GTID:1483306308492194Subject:Agricultural Soil and Water Engineering
Abstract/Summary:PDF Full Text Request
Agricultural water saving has always been a hot topic in the development of agricultural modernization,the efficiency of the utilization of channel water plays a vital role in agricultural water-saving irrigation,the problem of channel water loss often determines the efficiency of channel water utilization.So far,the common channel leakage loss calculation method based on the theory of soil moisture infiltration has problems such as complicated implementation,large workload,and large arbitrariness in the value of formula coefficients,and there are many factors that affect the two-dimensional infiltrationof the channel.How to deal with the two-dimensional infiltration characteristics and multiple influencing factors of irrigation canals,established a simple and reliable multi-factor mathematical model of soil water infiltration model parameters,further strengthen the calculation method of the canal leakage loss model parameters,in order to calculate efficiently and quickly,the channel water use efficiency is a research topic that needs in-depth discussion.This project is implemented as a series of indoor and outdoor static water test combined with HYDRUS-2D simulation testing,a two-dimensional multi-factor migration distance model of the moist peak in the channel was constructed,at the same time determine the moisture from the soil infiltration model;Then use the soil moisture infiltration model as the starting point for the study,these findings have both through canals test and theoretical analysis of soil moisture infiltration,exploreing every part of the different influencing factors which influence on the parameters of soil water infiltration model,to determine the multi-factor mathematical model of the canal soil water infiltration model parameters;Then combine the open channel uniform flow equation with the Kostiakov channel leakage loss model,establishing the mathematical relationship between coefficient of channel water coveyance loss and flow,proposed a simple algorithm for the soil permeability coefficient and index in the channel leakage loss model through the reverse solution;Made an integral method to get a new calculation method for channel leakage loss,and software was developed for programmatic calculation of channel water utilization efficiency.The main findings of this article are as follows:(1)The factors influencing the two-dimensional infiltration characteristics of channels was analyzed from the angle of static water method soil moisture infiltration test.A two-dimensional multi-factor migration distance model of the moist peak was established,and the change of horizontal and vertical migration distance of the moist peak defined by the width and depth ratio of the channel section ?=0.914 is proposed.Under the same factors and different treatment conditions,the soil water infiltration capacity showed different changes in different degrees,and the change of the slope coefficient had a relatively small effect on it.In addition,the dynamic changes of the soil moisture content of the canal bed were analyzed for different pressure heads,and the results showed that when the pressure head is less than 60cm,the channel water infiltration mainly enters the canal bottom soil through the vertical direction,and the volume of lateral infiltration water is small;The soil moisture content at 0.5m away from the center of the channel has the most dramatic change over time.(2)Based on the saturated-unsaturated soil water movement theory in the two-dimensional state,determine the soil water movement parameters by using methods of estimating initial values and correcting applied values,these boundary condations and initial conditions may serve to clarify the simulating soil water infiltration in the channel,the HYDRUS-2D model is selected for numerical simulation and verification analysis.The simulation results are basically consistent with the changes of the field measurement values on the whole,and the evaluation statistics are good,and the selected soil water mo vement equation is reasonable.It is seem feasible to study the canal leakage to evaluate the infiltration rate and cumulative infiltration amount.(3)Based on statistical methods and theoretical analysis,the dominant factors and models of canal soil water infiltration are determined.Using path analysis method to eliminate the factor of slope coefficient m,the total effect of soil clay content c,bulk density ?,initial water content ? channel depth h and bottom width w on the cumulative infiltration of soil water infiltration is-1.0456,-0.9952,-0.2138,0.7701 and 0.7565,the degree of influence is c>?>h>w>?.Using statistical indicators to evaluate the soil water infiltration model,the results shows that the Kostiakov-Lewis model can better simulate the soil water infiltration process under test conditions.(4)Based on the determined dominant factors of soil moisture infiltration and the Kostiakov-Lewis model,a multi-factor mathematical model of the infiltration parameters of the Kostiakov-Lewis model was established.Based on the results of HYDRUS-2D simulation of the actual channel,it is determined that the model infiltration parameters K,a,and ic are linearly correlated with the soil clay content c,bulk density ?,initial water content ? channel depth h and bottom width w,and enter the infiltration parameters can be expressed by the test factors c,? ?,h and w,in this way,the multi-factor mathematical calculation model of infiltration parameters were established and verified,thus the multi-factor mathematical model of kostiakov-Lewis model infiltration parameters are determined to be reliable.(5)Based on the multi-factor mathematical model of the Kostiakov-Lewis model infiltration parameters,combined with the open channel flow equation and the channel water loss equation,the calculation method of channel water utilization efficiency is proposed.The study analyzed and determined that the channel flow rate and the channel water loss coefficient per unit length shows a power relationship,and used the reverse method to solve the soil permeability parameters A and m of the Kostiakov channel leakage loss model,and then used the integral method to obtain the new channel water leakage loss calculation formula,and use Visual Basic high-level language programming to programmatically calculate channel water utilization efficiency.For this calculation method,a typical bucket and agricultural canal in Hetao Irrigation District are used as examples for verification.The error between the two is below 5%to determined the feasibility of the Kostiakov-Lewis improved model canal water use efficiency calculation method.The scientific research results of this paper showed that,the multi-factor migration model of 2D channel infiltration and the defined range of the width to depth ratio of the channel are of certain reference value for grasping the soil water infiltration characteristics of the channel.The integral method needs to determine the model parameters and channel gross flow to calculate the channel leakage loss.Combined with the compiled software,the channel water use efficiency can be calculated.This idea and method is suitable for evaluating the channel water use efficiency in most irrigation areas.
Keywords/Search Tags:HYDRUS-2D, Soil water infiltration model, Canal leakage loss model, Model parameter improvement, Canal water use efficiency, Calculation method
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