| As the core of the on going "Mountain greening and water clearing" project on whole loess plateau, recovery and reconstruction of vegetation, its way of plantation, pattern, and consequent interest of ecology and economy to vegetation is largely depended on the water resources bearing capacity of the region. In this paper, we have used field experimental data, field surveyed data and in the light of other research results to analysis behavior from rainwater to soil water in extent, directions and factors involved in this matter firstly. The author had also put forward the formation of soil water resources and its distribution patterns in the whole region. Form the point of view in system ecology and quantity ecology, the author do also analysis on spatial characters of soil water quantity and its yearly translated volume in the loess plateau, and hence to analysis the suitable vegetation division arrangement, to calculate the net primary productivity of vegetation, to answer the bearing capacity of soil water resources etc. Therefore the vegetation resumption can than be based on sound scientific basement. Through three years studying, the paper had made progress in some aspects.1. Systematically analysis the quantity of water reserved in soil and yearly amount of rainfall converted to soil waterBased on the systematic analysis of rainfall redistribution pattern (law) on slope, the author stated the methods for calculating yearly soil water volume, and then applied it for differential vegetation zone.Based on the systematic analysis of past soil water data, author had described the spatial distribution pattern of stored soil water, the soil water quantity (depth in mm) changes with latitude and longitude. It shows the quantity decreases from the east to the west, from the south to the north. It also differs with land use type: arable land>forestry land>shrub land>grass land.Taking the whole region mean to analysis, surface soil stored little less water, the 0-2m stratum stored available soil water is littler than 1/4 of precipitation; deeper layer stores more water, 3-5m stratum of that is 44%; and that of 0-5m account for 73% ,which amounted to 83% volume of soil converted rainfall. Soil water shortage is very serious.The total capacity for soil holding water is very huge. The water holding capacity is forestry zone> transition zone> pasture zone, that of 0-5m layer soil is respectively in fallow: 1417.5mm, 1234mm, 1050mm, the average of the whole region is about 1208.5mm, which are 2.45 times, 2.56 times, and3.15 times of its zone mean precipitation. The whole region's mean is 2.7times of the mean precipitation respectively.If the 45% land were covered by stone mountain with thin soil layer, or used as traffic land, residential land, the water resources in 0-5m layer of soil is about 2443.4*108m3, among those there is 1086.7*108m3 is available water, which account for about 40% of rainfall resources of the loess plateau.2. Clearer the water movement both in intensity and orientation by studying on rainfall redistribution on slopeThe mount of rainfall to soil water is affected largely by rainfall volume and its intensity, rainfall duration, slope gradient, position on slope, land use form, and land type,etcForm top to bottom of a slope, rainfall accepted by soil is different on different position. It grows along with slope length. K, refers to rate of rainfall accepted by soil, which is growing too. Forestry land and grassland have a higher Ka.Under the experiment condition, according to volume of soil gained rainfall, the sequence is drizzle, moderate rain and then heavy rain. The infiltration rate of them are respectively 71%, 66%, and 52%; the volume size also obeys to grass land>terrace land> terrace land with slope upside>hard lever land, the infiltration rate growing along with rainfall intensity decreasing.Affected by many factors including rainfall redistribution on slope, the soil water resources volume is terrace land with slope upside >terrace land>slope a...
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