Experimenting And Modelling On The Snowmelt Hydrological Process In Gurbantonggute Desert Of Xingjiang, China

Gurbantonggut desert, which is located in northwest of China, is the only one desert that existence steady snow cover in winter. Hydrological process becomes complicated and exceptive for its unusual landform, climate and different surface condition. Snow melt water is hard to form the surface runoff for its sand soil with high infiltration capacity and sand- ridge with arborization distribution. Additionally, vegetation and landform of Gurbantunggut desert result in non-uniformity of snow-cover and snow-melt process. However, it is lack for the research of snow-cover and snow-melt process within this area. Studying on snow-cover and snow-melt process within this area, It can help us to apprehend cause of formation of unusual landform within this area. it is significant for the study on ecological water requirement in arid land and regeneration of desert vegetation.The main study area is located in the southern edge of Gurbantonggut desert, which is belong to the experimental site established by Fukang Desert Ecosystem Research station,Chinese Academy of Sciences, . Based on field experiment in situ , snow investigation and the measure of soil physics characteristics parameter in the laboratory, snow physics characteristics, snow distribution pattern and its relation to vegetation are analysed, and the snow melt water infiltration process are simulated using the software of HYDRUS-1D/2D. The conclusions are illustrated as below:(1) The relation of snow distribution and vegetation Snow distribution pattern was described. Blowing snow is existence in January and February so as to the frequently happen of the gale. The characteristics of the distribution of desert snow, and the relation between snow depth of different places, different direction and height of tree is: snow at the foot of sand dune was more uniformity and deeper(18-20cm), snow at the top of sand dune was more shallower(15-17cm), and snow thickness of shady slopes (20-22cm) was deeper than that of sunny slopes (15-18cm). haloxylon ammodendrom effects snow distribution significantly in different landform condition. Southeast and east wind direction are universal in winter of Gurbantonggut desert. Snow in the northern side of stem of haloxylon ammodendrom at foot of sand dune is the deepest. The effect extension is 135cm when the tree height of haloxylon ammodendrom is 295cm. snow in the northern side of haloxylon ammodendrom in shady slope is thicker, and effect extension is 195-200cm when the tree height is 373cm, and effect extension of other three direction is 165cm. Effect of haloxylon ammodendrom at the top of sand dune on snow distribution of different direction is insignificant, and effect extension is 130cm as the height of haloxylon ammodendrom is 286cm. The larger crown of haloxylon ammodendrom, the wider effect extension. and snow within its vertical shadow is shallower.(2) The physical characteristics of snow-cover and snow-melt process From November to January is the snow accumulative period. the last ten-day of February to the first ten-day of March is the period of snow-melt, and the snow rapidly melt period is about 6 days, and the equivatent of the snow melt water is about 35.1mm.The variety range of snow density in different position in Gurbantonggut Desert: Foot of the sand dune is 0.1753- 0.2270g/cm3, Top of sand dune is 0.2026-0.2590g/cm3, Shady slopes and is 0.1704-0.2247g/cm3 and sunny slopes is 0.1972-0.2349g/cm3. In the begining of the snow melt period, the snow density at sunny slopes is higher than shpdy slopes, but it is change at a later period. Snow which is located in the sunny slopes melted early than the snow located in the foot and top of the sand dune two or three days.The infiltration process of snowmelt water Used the HYDRUS-1D/2D to simulate the infiltration of snowmelt water, and the average error between simulating data and measuring data is less than18%, individual is 20%. It is suitable that the HYDRUS-1D/2D can be used to simulate the process of the snowmelt water infiltration in desert. In early period of snowmelt (13th March),the soil moisture content is decreased along with the increase of different distance far from the stem and different depth of soil profile, the infiltration velocity of snowmelt water is more slower in the food of sand dune. After 13th March, the soil water content is increase stable and each layer delay about two days. The soilmoisture content of 40cm far from the stem which increase point lag the surface about 5days,only the soil water occur change about 50cm distances which from the surface to the underground. On the top of the sand dune, the distance more farther apart from the stem, the variety range more smaller, and the steady value of soil moisture content more shallower. The result proved the supply depth of snowmelt water is more shallower when the distance more farer apart from the stem. The infiltration of snowmelt water is influenced by vegetation more evidently, it is not only impact the supply quantity, but also influence the supply depth.