Shapotou Desert Spring Water Content Of The Sand Layer And Moisture Content

The moisture is restraint to vegetation construction and desertification governance in desert regions. Based on several field on-site inspection, this paper selected the representative great moving dunes, depressions and semifixed dune in the study area for moisture content research. Through moisture content determination of 32 drilling profile in different aspect, different locations and different types of sand dunes of the moving dune in Shapotou area, the changes in moisture content, water sources, the form of water, water balance, the water cycle and other issues of the sand in the area in spring was researched, and The main conclusions are as follows:(1) The moisture content in the top of the great sand dunes is below 1.0% in general. The water content is commonly between 1.0% and 2.0% in the central section, while 2.0% and 3.0% in the bottom generally. In semifixed dune,the moisture content is between 3.0% and 2.0% in commonly, and in the depth of less than 2.0m of the depression sand, the water content is generally between 2.0% and 3.0%, while in the depth between 2.0 and 3.0m, the groundwater that the moisture content is higher than 20% often appear.The Sand moisture content in the windward slope is above that in the leeward slope of the large sand dunes. The water content of the sand dunes are the highest in the bottom, followed the central, then the lowest at the top.(2) Vertical moisture changes in sand layer of great moving dune and semifixed dune can be divided into four levels, layer 1 is active one for the moisture change, which is about 0.4m depth from the surface. Layer 2 is slow one for the moisture change, which in the 0.5m to 1.0m depth around the folowing. Layer 3 is more stable one for the moisture change, which in the 1.0m to 2.0m depth around the folowing. Layer 4 is deep stable one, which below the depth of 2.0m.to 4.0m.(3) We found that the moisture of moving dune and semifixed dune existed mainly in the form of film water, only in the depths of depression, the bulk water and groundwater can be seen, they converted from the film water and the moisture content more than 5.0%. In addition, the miosture content and thickness of film water would increased and converted into the bulk water when the film water infiltrate into near the groundwater table, and the film water, even become recharge resource of groundwater.(4) According to the principal origin of moisture in sand layer is atmospheric precipitation, we can confirm that moisture in sand layer in autumn more than in spring in Shapotou area. In Shapotou area, the moisture in sand layers has a trait of positive balance, this is mainly decided from the rapid infiltration of moisture in sand layers and the depth affected by evaporation of sand layers is little, which belonged to the type of moisture positive balance of rapid infiltration and evaporation was less.(5) In Shapotou area, moisture content in sand layer was changed with the terrain height, from high to low in turn register as depression, bottom, middle and top. And the depression or flat lots is the main infiltration channels downward of atmospheric precipitation.(6) Dried sand layer has an important role in the process of moisture convertion. We have an preliminary judgment that combined with the boundary depth of distribution of dried sand layer and natural conditions in Shapotou area, the thickness of dried sand layer was less, generally between 10 and 15cm. The thickness of dried sand layer was less which showed that the depth affected by evaporation of sand layers was little, what is an significant reason that desert area was flush of groundwater.