(2) 雪融水在垂直入渗的同时，存在沿沙丘坡面方向的侧向流。2013年冬季累计积雪40 mm (雪水当量)，侧向运移距离29.72~45.60 cm，侧向流流量1.08×10-3 m3/d。融雪期结束后，坡脚处43.97%的土壤水分来源于坡面侧向流补给。可见，雪融水侧向运移是坡脚土壤水分富集的重要原因。
(3) 研究区2003~2013年间最大自然降雨强度是14 mm/h，远小于裸露沙地平均土壤稳定入渗率(7.45 mm/min)，自然条件下，降雨以垂直入渗为主，裸露沙丘坡面难易形成地表径流和沿坡向的壤中流。
(4) 人工强降雨模拟实验表明，在降雨后期，沙丘存在壤中侧向流，侧向流水量陡坡大于缓坡，土壤水分富集层深度陡坡大于缓坡，土壤水分富集区域位置陡坡比缓坡偏下。在雨强0.52 mm/min、雨量20.9 mm的情况下，陡坡和缓坡的侧向流对下部1 m深土壤剖面补给水量分别为8.68 mm和4.66 mm，分别占其土壤水分总储量补给的37.32%和32.63%。|
|其他摘要||Water is the main driving factor to the vegetation succession in desert ecosystem. The soil moisture in Gurbantunggut Desert mainly comes from winter snow cover melting primarily in spring and rainfall. Many factors such as vegetation, topography, underlying surface conditions and so on, affect the soil moisture, which result in its spatial distribution variation in local areas and accumulation at the foot of sand dune. The study of lateral water flow deriving from snowmelt water and rainfall contributes to digest the process of rainfall conversion and soil moisture redistribution as well as the cause of soil moisture accumulation at the foot of sand dune further. Up to now, quantitative researches of lateral water flow in Gurbantunggut Desert have been largely neglected.
At dendritic sand dune in south of Gurbantunggut Desert, we carried out continuous observation of dynamic variations of soil moisture and brilliant blue traced experiment during snow melting period or after rainfal for exploring the migration path of snowmelt water in soil layer and quantifing the lateral flow at the sametime. Meanwhile, through the simulated rainfall experiment of different rainfall amount and intensity, we analyzed the producing conditions of lateral water flow resulting from rainfall. The main results are as follows:
(1) The uniformity coefficient (K) was greater than 0.9, which mean that spatial distributions of snow cover were homogeneous on sand dune scales. So the features of spatial distribution of snow cover weren’t the factors causing evident spatial variation in soil moisture of sand dune.
(2) Snowmelt on the sand dune infiltrated vertically and migrated laterally. The lateral migration distance was in the range of 29.72~45.60 cm when the accumulation of snow cover is 40 mm (snow water equivalent). Snowmelt water amount of lateral flow was 1.08×10-3 m3/d. The contribution of soil water at the foot of sand dune derived from snowmelt lateral flow was 43.29%, indicating that snowmelt lateral migration was an important factor for the accumulation of soil water at the foot of sand dune.
(3) Bare sandy land had an average soil infiltration rate of 7.45 mm/min, which is bigger than the strongest rainfall intensity (14 mm/h) during the period of 2003 - 2013 in this study region. It means that rainfall mostly infiltrated vertically under natural conditions, which result in less overland runoff and interflow along the slope direction of bare sandy dune.
(4) The outcomes of simulated strong rainfall show that soil moisture migrated laterally apparently after rainfall. The depth of soil moisture accumulation layer on the gentle slope was greater than that on the steep slope. Meanwhile, the enrichment area of soil moisture was respectively located at middle and lower parts of slope. When rainfall intensity is 0.52 mm/min and rainfall amount is 0.52 mm/min, amounts of lateral water flow were 8.68 mm and 4.66 mm in 0~100 cm horizon, respectively, accounting for 37.32% and 32.63% of total soil water source in the lowland respectively.|
刘昊. 古尔班通古特沙漠沙丘坡面侧向流研究[D]. 北京. 中国科学院大学,2015.