| Water resource is an essential and important resource in human production and life.With the rapid increase of people’s demand for water resource,it has become an important issue to rationally utilize agricultural water resource and improve the irrigation efficiency of water resource in China.Canal leakage is an important basis for irrigation water utilization efficiency,canal anti-seepage effect evaluation,irrigation district planning and design,etc.Based on the laboratory test,the HYDRUS-3D software was used to simulate the test process.The seepage loss of the channel was calculated by the infiltration model,and the influencing factors of the soil water infiltration process were analyzed to explore the variation rule of the soil water infiltration characteristics of the channel.By comparing the actual observed values in the laboratory test with the numerical software simulation values,the influences of channels with different sections,soil texture,initial moisture content,infiltration head and wet cycle on cumulative infiltration volume,migration distance of wetting front and infiltration rate were analyzed.The main research results are as follows:(1)According to the grain size analysis and the soil texture classification standard of USDA,the soil samples were divided into loam,silty loam and clay loam.The saturated water content of the soil samples was determined,including 49.1%in the loam,42.3%in the silty loam and 44.7%in the clay loam.The saturated water conductivity of the soil samples was 0.163cm/min in the loam,0.030cm/min in the silty loam and 0.024cm/min in the clay loam.(2)The three-dimensional unsaturated soil water motion equation was established,and the HYDRUS-3D software was used to solve the soil water motion equation under the test conditions,and the accuracy of the three-dimensional unsaturated soil water motion equation and model simulation was verified.Root mean square error(RMSE),mean absolute error(MAE)and determination coefficient(R~2)were calculated by comparing the observed values and simulated values of cumulative infiltration volume,wetting front migration and infiltration rate in laboratory experiments.The RMSE value of U-shaped channel ranged from 69.59-412.18m L,with an average value of 205.95m L.The MAE values ranged from 1.50-10.04m L,with an average value of 4.47m L.The R~2 values ranged from 0.84-0.99.The RMSE values of trapezoidal channels ranged from 84.29-449.63m L,with an average value of 255.35m L.The MAE values ranged from 2.38-9.49 m L,with a mean value of 4.54m L.The R~2 values ranged from 0.83-0.98.It shows that the selection of soil moisture movement parameters is reasonable and the model can be used to simulate the process of soil moisture movement under experimental conditions.(3)Under the condition of trapezoidal channel,soil texture and wet front migration have significant effect on cumulative infiltration,infiltration head has significant effect on cumulative infiltration,and initial water content has no significant effect on cumulative infiltration.The influence of soil texture on the migration distance of wet front is very significant,the influence of infiltration water head and wet front migration on the migration distance of wet front is significant,and the influence of initial water content on the migration distance of wet front is not significant.Soil texture has a significant effect on infiltration rate,initial water content and wet front migration have significant effects on infiltration rate,and infiltration head has no significant effect on infiltration rate.The cumulative infiltration amount and the migration distance of wetting front are positively correlated with the infiltration head and the wetted front migration.The cumulative infiltration amount,the migration distance and the infiltration rate of the wetting front are the minimum in the loam soil,while the cumulative infiltration amount,the migration distance and the infiltration rate of the wetting front are the maximum in the loam soil.The infiltration rate is positively correlated with the moisture perimetry,but negatively correlated with the initial moisture content,which has a great influence on the initial infiltration rate.(4)Under the U-shaped channel condition,soil texture has a significant effect on the cumulative infiltration amount and the migration distance of the wetting front,infiltration head and wet cycle have a significant effect on the cumulative infiltration amount and the migration distance of the wetting front,and the initial water content has no significant effect on the cumulative infiltration amount and the migration distance of the wetting front.Soil texture has a significant effect on infiltration rate,initial water content and wet front migration have significant effects on infiltration rate,and infiltration head has no significant effect on infiltration rate.(5)In the process of farmland water transmission channel construction,the use of trapezoidal channel will have a great impact on the irrigation process,and significantly increase the irrigation water consumption.Loam soil can be used to lay trapezoidal channels in the construction of large-scale irrigation water delivery channels,in which the initial moisture content is 5%,the height of the infiltration water head is 6cm,and the wet front migration is 35cm.At the same time,some deep-root plants can be planted around the channels to supply the seepage water to plants,so as to improve the utilization rate of the seepage water.However,in the construction of small water delivery channels,the total amount of irrigation is small,so priority should be given to U-shaped channels paved with clay loam,where:The initial soil moisture content is 5%,the height of infiltration water head is 6cm,and the wet front migration is 35cm,which can reduce the leakage of the channel.At the same time,some shallow-rooted plants can be planted around the channel to supply more water resources to the plants and reduce unnecessary waste,so as to improve the utilization efficiency of water resources. |
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