Rainfall Infiltration And Soil Water Dynamics Under Interval Coverage

It is short of water resources in arid and semi-arid area, the rainfall is the major source ofwater. Rainfall averages out in this part of the country is at300mm to550mm a year, rainfalldistribution is not uniform in spatial and temporal, supply and demand are not synchronous.Low rate of rainwater use, high soil surface evaporation and soil erosion and water runoff aremain problems in the Loess Plateau regions, which restrict the sustainable development ofagriculture. Sloping field is main soil and water losses area and agricultural land in LoessPlateau. The lost runoff plays an important role in the impacts of soil and water loss on landproductivity of sloping field.In this study, based on the main problems of the slope land in arid and semi-arid area,using indoor artificial rainfall simulation, water infiltration property and spatial soil waterdistribution were investigated under alternative coverage on Lou soil and Loess soil underdifferent rainfall intensities, slopes and area ratios. The purpose was to make more simulationunder the control test conditions, which had theoretical significance for interval coverageapplication.This study mainly discussed the impact of soil water distribution factors under laboratoryexperiments and field tests. We get the following conclusions through the experiment:1Soil infiltration capabilityUnder one-dimension vertical water-ponded infiltration at laboratory, cumulativeinfiltration increased with the increase of time, in the same time, cumulative infiltration andinfiltration rate of Loess soil were higher than Lou soil. cumulative infiltration and infiltrationrate can be simulated with Philip model.Under different rainfall intensity, Initial infiltration rate depended on rainfall intensity,stable infiltration rates have the same value because they were influenced by the propertyparameters. Cumulative infiltration decreased gradually as the rainfall intensity increased.Cumulative infiltration and infiltration rate of Lou soil decreased first and then increased asthe slopes increased, and there is a critical slope when the slope is15degree. Cumulativeinfiltration and infiltration rate increased as the area ratio increased. Coverage treatments werehigher than CK treatment. It can be speculated that interval coverage can increase rainfallinfiltration. Soil infiltration rate and cumulative infiltration of Loess soil did not showobviousdifference between different slopes.Runoff-ponding method can fit the dynamic change of infiltration rate.2Soil water distributions on slope under alternative coverageRunoff advance speed increased as rainfall intensity and area ratio increased. Within therunoff advance speed area, cumulative infiltration decreased and changed gently as the arearatio increased. Runoff advance speed did not show obvious difference between differentslopes. Under the same condition, runoff advance speed of Lou soil was faster than that ofLoess soil, and the cumulative infiltration of Lou was smaller than that of Loess soil.The maximum depth of wetting front was located at the conjunction point of coveragearea and infiltration area. Depth of wetting front and wetted area decreased as the rainfallintensity and area ratio increased, did not show obvious difference between different slopes.Comparing the wetting front depth of Loess soil and Lou soil, the result showed that thewetting front depth of Loess soil was deeper than that of Lou soil. Wetted area was relatedpower function with cumulative infiltration.The maximum and minimum wetting front uniformity coefficient of Lou soil and Loesssoil appeared when the rainfall intensity was60mm/h and25mm/h respectively.The wetting front uniformity coefficient of CK treatment was higher than that of coveragetreatments. The wetting front uniformity coefficient of Lou soil was smaller than that of Loesssoil (Except for CK treatment).3Field Test of interval coverage methodCovering the upper part of slope may decrease soil evaporation of the covering region andretain higher soil moisture content in soil surface layer. But soil moisture content reducedgradually with the depth of soil layer.Interval coverage method could increase the soil moisture content on the border of thecovering region and the soil uncovered region or the plant growing region.The runoff that the covering region collects could improve soil moisture content of the soiluncovered region.