Study On Soil Resistivity Characteristics And Its Application In Loess Region

Soil moisture is the main limiting factor of vegetation restoration and sustainability in arid and semi-arid loess regions.Sloping land and dam land are typical geographical units of small watershed on Loess Plateau.It is of great significance for ecological restoration and agricultural production of small watershed to grasp the quantity and spatial distribution characteristics of soil water in deep layer of sloping land and dam land.In this study,the application and progress of Electrical Resistivity Tomography method(ERT)in soil hydrology is systematically combed by using the technical literature mining and visualization tool Cite Space.In order to verify the applicability of the ERT in the deep loess area of the Loess Plateau and clarify the distribution characteristics of soil water resources on typical dam land and sloping land on the Loess Plateau,the deep soil resistivity(ρ)of 7 typical dam land in different climatic regions of Loess Plateau and typical slope land in Shenmu Liudaogou small watershed in northern Shaanxi was measured by ERT.The spatial distribution characteristics ofρbetween different dam sites and between dam sites and slope sites were compared and analyzed.Based on the measured soil water content(θ)data of slope sites and dam sites,Then,the soil resistivity(ρ)of 5 typical climatic regions of Loess Plateau and Liudaogou small watershed in northern Shaanxi was measured by ERT.Theρdistribution characteristics of typical slope and dam in Liudaogou small watershed were studied and the relationship betweenρandθwas established.Meanwhile soil water storage(SWS)of 0～12.5m profile and its spatial distribution were quantified.Finally,the effects of fertilization onρwere studied in Changwu farmland.The main conclusions were as follows:(1)Theρdistribution of slope is significantly affected by slope position,Along the slope,theρdistribution is slope top>slope middle>slope bottom,which is related to vegetation water consumption and precipitation redistribution process on slope surface;But theρdistribution of dam land is complex,and is affected by many factors such as climate,soil texture,land use type,bedrock depth and dam land structure.The distribution pattern ofρin the vertical direction of dam land is“high-low-high”.The dam has obvious saturated and unsaturated layers,while the slope is unsaturated layer;(2)There is a significant power function relationship betweenρandθin typical slope land and dam land in different climate zones.The soil water storage of 0～12.5 m on the dam land and slope with similar area are 6.59×10~4 m~3 and 2.59×10~4 m~3 respectively.The water storage capacity of the dam land is 2.6 times that of the slope land;(3)The spatial distribution characteristics ofρare different among different dam land on the Loess Plateau,indicating that the occurrence types of water resources in different dam land may be different.Based on the shallow groundwater level,θandρdata observed in dam land,the occurrence types of water resources in dam land can be roughly divided into three types:1)the whole dam is completely unsaturated;2)The whole dam area is close to saturation;3)The surface layer is not saturated,the middle layer is close to full,and the bottom is not full;(4)ERT can accurately invert SWS and its spatial distribution in the deep loess region,and identify the interface between unsaturated zone and bedrock in the saturated zone of soil water.However,for the farmland ecosystem,the high salinity of soil caused by long-term fertilization may change the originalρdistribution characteristics,and affect the quantitative relationship between ρ and θ.