| Dongzhi tableland is the largest and most continuous tableland surface on the CLP,which is also known as "the first Loess tableland in the world".During history,increase of human activities has aggravated the headward erosion of the Dongzhi tableland,which has been significantly fragmented the tableland surface.In the tableland,the headward erosion is closely related to the hydrodynamic conditions of the tableland surface and gullies.The project of Gully Consolidation and Tableland Protection(GCTP)is an important measure to control headward erosion and reduce soil and water loss in the tableland area,including biological and engineering measures.Biological measures mainly include natural vegetation restoration and artificial plantation.The main engineering measures are backfilling and reinforcement of gully head to prevent the advance of gully head and suppress geological disasters.However,the difference of soil moisture field under different GCTP measures has important guiding significance for understanding the development of rainfall infiltration,soil moisture migration and erosion disaster on the loess tableland.Therefore,this study takes the biological and engineering control of headward erosion on the Dongzhi tableland as an example and the technique of electrical resistivity tomography(ERT)is applied to quantify soil moisture and infiltration difference between the natural and human measures.Firstly,the relationships between ERT data and soil moisture measurement data were analyzed and the model were built.Secondly,the differences of spatial and temporal variations of soil moisture between natural regrowth of grasses and afforestation hillslopes were investigated.Thirdly,the differences of spatial and temporal variations of soil moisture between backfilled tableland and original tableland were investigated and water infiltration patterns in heavy rainfall was measured.The results are as the follow:(1)The power function model of soil resistivity and water content is established,which is suitable for the area of Dongzhi tableland.Moreover,the accuracy and applicability of the model is tested,which provides a basis for the data inversion of soil moisture field.(2)In the biological measures of GCTP,vegetation types affected both shallow(0 ? 5 m)and deep(> 5 m)soil moisture patterns,but its impacts on the shallow soil moisture was much greater than that on the deep soil moisture.The cultivated land showed the highest content of soil moisture,which followed by grassland and woodland.Topography has a significant effect on both shallow and deep soil moisture.The shallow soil moisture in the hilltop is greater than that in the hillslope,and the gully bottom showed the highest content of soil moisture both in the shallow and deep soil layers.The greater the slope gradient,the lower the shallow soil moisture content;the lower the altitude,the higher the deep soil moisture content.In different vegetation and topographic locations,the seasonal changes of shallow and deep soil moisture were not synchronous.Soil moisture in the shallow layer showed obvious seasonal characteristics,while the deep soil moisture did not change with the season and showed a relatively stable pattern.(3)In the engineering measures of GCTP,the relative impermeable layer(3 ? 7 m)exists in the artificial backfill area,but not in the non-backfill area.In the dry season,which was mainly affected by evaporation,the soil moisture in the backfilled area decreased obviously with time in the depth of 7 m,and the average change rate of soil moisture was-12.10%,which demonstrated that intense evaporation has an obvious effect on the relative impermeable layer in the backfilled area;In the rainy season,which was mainly affected by rainfall infiltration,the soil moisture in the backfilled area increased obviously with time in the depth of 3 m,and the average change rate of soil moisture was + 13.00%,The abundant rainfall has no obvious effect on the relative impermeable layer of the backfilled area.The soil moisture content in the backfill area with drainage pipeline is more than 20%,which is obviously higher than that in other areas of the water profile,and the maximum change rate of soil moisture content in this area is + 30%,so leakage may occur in the drainage pipeline.The soil moisture field before and after the heavy rainfall(62.8 mm)showed that 24 hours after the rainfall.Under heavy rainfall,the degree of rainfall infiltration and redistribution on the original and backfilled tableland are obviously different.The increase rate of soil moisture in the upper layer of the original tableland is 23.64%,which is much higher than that of the backfilled tableland(6.76%). |
PDF Full Text Request