Study On Disciplines And Affecting Factors Of Soil Moisture Distribution At Unsatutated Zone In Arid And Semi-arid Areas

Under extreme drought conditions, water is the main factor affecting the environment which limits the type and quantity of perennials. Vadose zone collecting atmospheric water-plant water-surface water-groundwater constitutes a dynamic cycle of water bonds, and unsaturated zone water has a very important influence on development and utilization of water resources, environmental protection and pollution forecasting quality with the migration flow. This paper studys on soil moisture distribution and Composition of soil water energy at unsaturated zone in arid and semi-arid areas.The results are as follows:Dune water content displayes logarithmic distribution vertically in the south of lake-intensive areas of BadainJaran Desert, whereas soil water content in dunes farther away from the lakes displays, logarithmic normal distribution, Soil water mass content characteristics are logarithmic in the more arid Potou wasteland, sand and non-cultivated soil in Loess Plateau in eastern Gansu, while moisture content of the arable soil effected by its soil texture, displays quite different.The proportion of solute potential displays increasing from semi-arid areas to arid areas. In Loess Plateau unsaturated zone, the proportion of solute potential is about 15%at Potou wasteland, while which can be up to about 25%in the farm land. Matric potential accounted for nearly 80%in potou of the arable and is 60%in average content in farm land, which is of the largest proportion of the soil water pertential. Soluble solutes accumulate at the 5-10cm near the surface due to strong surface evaporation. The proportion of solute potentials are about 75%and matric potential are about 25%in the surface of Badain Jaran Desert; also pertentials account for about 40%below the accumulated zone. HCO3- plays a leading role of anios the solute potential of the unsaturated zone, leading cation is Ca2+in the loess area, while K+in the desert. Soil solute potential in the weight of the plasma ions is the largest HCO3-and Ca2+, which is about 50%and 25%respectively of the solute potential in the Loess Plateau, Na+and Cl- are about 10%. Soil water potential in the weight of the solute largest ions forming solutes pertential are HCO3-and Na+at vadose zone of Badain Jaran desert, which are about 45%and 28%respectively; Ca2+has a larger proportion about more than 10%; Cl-and K+displaying relatively high proportion are about 6%and 5%.