沙坡头沙漠春季沙层含水量与含水条件研究

【作者】 郁科科；

【导师】 赵景波；

【作者基本信息】 陕西师范大学 ， 环境科学， 2011， 硕士

【摘要】 水分是沙漠地区植被建设和沙漠化治理的制约因素。本文在数次野外实地考察的基础之上,在研究区选择具有代表性的高大流动沙丘、洼地和半固定沙丘进行含水量研究。通过对沙坡头区流动沙丘不同坡向、不同部位和不同类型沙丘32个钻孔剖面水分含量测定,研究了该区春季沙层水分含量变化、水分来源、水分存在形式、水分平衡和水循环等问题,得出以下主要结论：(1)大沙丘顶部沙层水分含量一般在1.0%以下,中部沙层水分含量一般在1.0%-2.0%之间,底部沙层水分含量一般在2.0%-3.0%之间。半固定沙丘沙层水分含量一般在2.0%-3.0%之间,汁地沙层2.0mm深度以内水分含量一般在2.0%～3.0%之间,洼地沙层2.0-3.0m左右深度常出现水分含量高于20%的地下水。大沙丘的迎风坡水分含量高于背风坡,沙丘水分含量都是底部最高,中部次之,顶部最低。(2)流动大沙丘和半固定沙丘沙层水分垂直变化均可划分为4个层次,第1层为水分变化活跃层,该层从表层以下至0.4m深度左右。第2层为水分缓慢变化层,在0.5m以下至1.0m深度左右。第3层为水分变化较稳定层,该层在1.0m以下至2.0m深度左右。第4层为深部稳定层,该层在2.Orm以下至4.0m深度。(3)大沙丘和半固定沙丘沙层水分均以薄膜水形式存在,只有在洼地较深处才能见到高于5%的由薄膜水转变而成的重力水和地下水。(4)沙坡头区沙层水分的主要来源是大气降水,秋季沙层水分含量高于春季。沙坡头区沙层水分具有正平衡特点,主要是由于沙层的高渗透率和沙层受蒸发作用影响深度小而出现水分正平衡,属于快速入渗和蒸发少型的水分正平衡。(5)沙坡头地区沙层水分含量随地形高度变化而变化,表现为沙顶部<中部<底部<洼地。低洼处或平坦处是大气降水向地下运移入渗的渠道。(6)结合干沙层分布的下限深度与沙坡头地区自然条件初步判断,该区干沙层厚度较小,一般在10-15cm之间。干沙层厚度小表明蒸发作用影响深度小,这是沙漠区地下水较丰富的重要原因。更多还原

【Abstract】 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.更多还原