Qinghai Lake Basin In The Northwest And Vertical Distribution Of Soil Water

In recent years, with the ecological problems of grassland degradation, desertification, reduction in wetland area, the lake water level drops, the shrink of the area appeared in the Qinghai Lake basin,which have effected the sustainable development of ecological environment and social-economic. In this context,choose five sites respectively in the north of Shaliuhe town, in the north of Shaliuhe villiage, Sidadui of Farm,First Qidaoban and First Wudaoban to carry on the open country sample and soil moisture content determination, study the characteristics of Soil moisture profile distribution, Dried soil layer distribution, formation of soil moisture, soil water balance and water cycle, the reason of grassland desertification and vegetation construction and other issues in the northwest of Qinghai Lake Basin.The study reached the following main conclusions:(1) The soil moisture content of research area reduces with increase of soil layer depth. Thick soil of the upper30cm of average soil moisture content is5.5%higher than30cm thickness of the thin soil moisture content. The negative pressure value of soil changes at0.16～0.42bar, generally0.16～20bar on determination period. The soil suction indicated that soil field capacity is about20%in the northwest of Qinghai Lake basin.(2) General development of dry soil layers in the study area. Distribution of dry soil layers in the area is very shallow, generally60cm depth. Dry layer level are mainly the mild dry layer and moderately dry layer, dried soil layer development strength increases with increasing depth.(3) According to the thick soil layer moisture content determination material of Qinghai Lake basin, establish the mathematical model by soil moisture varies with depth W=a h k of the soil below40cm. The model can be a good description of the characteristics of the soil moisture varies with depth.(4) The precipitation which infiltrated to the deep underground was blocked by soil dry layer in the northwest of Qinghai Lake basin. And generally can not recharge of groundwater which show that water circulation type in the area is abnormal water cycle.(5) There are four sampling points in the upper part of the soil water content greater than20%of the gravity water all at First Wudaoban, First Qidaoban in Tianjun County Qinghai Lake sand Sidadui of Farm, Shaliuhe town North of Gangcha County in Qinghai Lake basin.(6) The upper part of the soil water storage capacity was more and the middle and down water was less in the region which is suitable for the growth of grassland vegetation, and not conducive to the growth of forest roots of woody plants. The proposed the development of slow growth, short roots, less water consumption grassland vegetation in the region.(7) According to the analysis of soil moisture data of the Northwest of Qinghai Lake basin can determine that overgrazing are the main causes of desertification of grassland in the region, the impact of climate warming on desertification is secondary.