| Forests and water are important compositions of forest ecosystem, moreover, they are the most fundamental condition for the life and development of human being. The relationship between forests and water is one of key problems of the present research in forestry and ecology. Therefore, in one hand, the concept, development and application of forest hydrology are introduced in this paper. The relationship between forests and water are analyzed. The new research progress in the effect of forest on rainfall, interception annual runoff, was summarized. The main issues show that the most function of forest vegetation aims at protecting water resources and water environment, adjusting water amount, controlling erosion, decreasing run-off silt, decreasing maximum flow as well as increasing discharge of river in dry season and purifying water quality. On the other hand, the research of "Forests and Water" is from the aspects of the eco-hydrological models of forest ecosystem from, the viewpoint of forest ecosystem and combining with the research on forest structure, function, productivity, energy and material circulation, to explore the laws and internal relation of various forest hydrological phenomenon is the basic topic of research.1 .Based on the data of analysis, using theories and methods of mathematical statistics, two of interception models by canopy of Picea crassifolia are established as follows: the regression model on the relationship between penetration rainfall (P,) inside forest and total rainfall (P) outside of forest: Pj=0.8245P-1.372 (R=0.99); the model on the relationship between interception rate (IR) and rainfall: IR=-10.7111n(P). (R=0.7524) The results show that penetration rainfall inside forest increases with total rainfall outside of forest in linearity, and to certain extent, penetration rainfall inside by canopy also increases with total rainfall outside; the correlations of the interception rate to rainfall and intensity of rainfall are significant and the intercepted rate by canopy of Picea crassifrlia is diminished with the increase of rainfall and rainfall intensity, and increase with the increase of canopy density.2.By detection and analysis on litter accumulation, water梙olding capacity of the litter and interception of main types of forests, its waterolding capacity, intercepting role, water storage and soil reduction of litter were studied. It was considered that the hydro?ecological function of litter was finally embodied by the effect of water and soil conservation and the conservation of headwaters.3.By longerm located researches of the four main vegetation types, i. e. ,Picea crassifolia forest, Sabina przewalskii forest, shrubs and grazing land, soil water dynamicswas revealed. Transformation feature and availability of water moisture content for main vegetation type were studied and evaluated. The correlations between the cycle levels of soil water, stored soil water at the end of growing season were significant. The both consumption and compensation of soil water also were controlled by precipitation. On the other hand for four main vegetation typies, which are Picea crassifolia, forests Sabina przewalskii forests, bushes and pastureland, whose soil permeability function was analyzed from angle of its physics, capacity of water, storing water in it. The results show as follow: permeability function of soil is controlled by quality of soil hole. The quality and quantity of soil hole under Picea crassifolia forests are the best, and the permeability also is the best. Permeability of bush soil is the second, however, because of its special location and large area, their real storing water in soil is the most.4.The study on the frozen soil feature and its influence on the runfall of the catchment in Qilian Mountains. The results indicated that the soil begins to freeze around October 20,and finishes melting around August 20 of next year. Altitude slope side, vegetation condition of the land and temperature are the factors influencing the depth and the time of soil...
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