| Forest water-holding capability is the interception and storage function to the precipitation of forest ecosystem and one of the main ecological functions of forest. In the past, the main research was about the facets of theory of forest water-holding capability. The less study was about water-holding capability of different forest types and different growth stage of the same forest type. The universal application model to the optimum forestry coverage and spatial layout of water-holding forest was not still proposed. The more study was limited to the observation for catchment's area and the comparison experiment for small basin and it was not consider geography of basin fully, it was not representative and adapt to study water-holding function about big basin. And at present from the angle of whole and system how to evaluate water-holding function scientifically and impersonally to compare the magnitude of water-holding capability of different forest types which is not a perfect method. Based on the above question, by means of 3S technology and multianalysis mathematics method, using a few survey data in field and the information of RS and GIS, depending on the index and method of combined qualitative and quantitative, the quantitative estimation model is set up by pixel unit. The quantitative estimation of water-holding capability comes to the truth in the middle scale region. It provide the science foundation to optimize its spatial layout and forest structure, adjust forest layout, enhance water-holding capability of basins, set up health system of water resource protection forest on the basis of scientific management. The main research achievements are as following:Through the field survey for GongBieLa basin, the typical ground object control points and ground object points on relief map are not matched because of the effect of regional natural condition. It is very difficult to find out the control points and let the error less than one pixel when we use relief map to start satellite image geometry rectification due to too old relief maps and measure error of relief maps. So, the project study acquires position parameter, solves the problem of position precision, reachs to 2 to 5 meter's position precision, meet the demand of the research by DGPS.By using RS soft (ERDAS IMAGINE) and GIS soft (ARC/INFO), The satellite image geometry rectification and all kinds of basic handling are finished and the corresponding RS and GIS information are obtained to provide a great deal datas for model.Taking the RS and GIS data as information origin, using the multianalysis-linear mathematics methods, it produces the quantitative indexes system based on the RS and GIS information, setups the quantitative estimation model of water-holding capability degree, fulfills the quantity of water-holding capability.
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