The Curing Modes And DSS Of Small Watershed In Three Gorges Reservoir Area

The administration of the small watershed, which bases on adjusting the industrial structure and choosing the optimum pattern for the land utilization and the invest distribution, is a series of activities or courses which always adapt comprehensive ways, such as engineering, biological and agricultural methods, to change the location into an area rich of economical plants, protecting plants and plants for sightseeing, so that the agriculture, forestry and stockbreeding can developing in balance, and the industry and commerce can undergoing under a good artificial eco-economical system. The research of the small watershed administrating, nowadays, are concentrating at the follow aspects: the first one takes the engineering processes and trees-planting as the main treatments to protect the small watershed from the flood and solifluction; the second one researches the soil erosion principles of the slop land of the small watershed, such as the characteristics and affecting factors of the flow of mud and stone, the water flow and the loss of nutrient respectively, and the relationship among them, according to the knowledge of hydrology, geography and water conservancy; the third and the last one uses the method of gradations-analyzing and obscure-clustering to research the classification of the small watershed and its optimum using model in small dimension, which would company with the problem of how to change it into big reasonable dimension. There are many complicated types of small watersheds scattering in the mountain area of the three-gorge reservoir area, which mainly produce the loss the soil. It, on the other hand, can be help to ease the shortage of the land in the three-gorge area, if being developed. But till now, there is no study on the small watershed administration in this area to provide reasonable advices for the building of the three-gorge engineering and the protection from its water and soil loss, furthermore the comprehensive usage to the soil and water. Decision supporting system (DSS) can provide the officials with supports and help when making decisions, through analyzing model flexibly and rapidly. Such system highlights on the comprehensive utilization of various new techniques, such as GDSS, IDSS, DDSS and SDSS, in order to continuously meet different needs, and needs from different gradations of the government, which means the tendency of developmentof the decision-making supporting system.This paper focuses on the classification of small watershed investigation in the mountain area, the research of the optimum model for utilization, and the research of the supporting system for decision by adapting GIS techniques. It's aimed at grasping the number of small watershed, the inducing factors and the level of the soil erosion in this area, in order to build supporting systems fitting to decisions that are related to the administration of the small watershed, and propose the optimum model to administration this kind of land in the three-gorge area. The main achievements was listed as follow:(1) The analyzing of the characteristics of the small watershed in the three-gorge areaUtilization GIS techniques and its mathematical model to predict the amount of the loss of water, soil and nutrient of the three-gorge area based on analyzing the characteristics forming the local landscape of the small watershed. Then, combining with the distribution of the natural resources and the structure of society economy of a typical small watershed, the administrating model for every part of the small watershed and their developing strategies are proposed further. ? The landscape of the small watershed was making by coordination of the inner driving stress and the outer driving one. The inner stress, such as the geological structure, formed its basic skeleton; and the outer ones, such as weather and hydrology, continuously modified the landscape, and even played a main role in the later evolution of the landscape of this kind region. There were four stages in the evolution of the small watershed, when took the time as the dimension: Stage of controlling the structure formed the basic skeleton of the landscape, Stage of free development reformed the landscape by the driver of the inner stress and in the stage of controlling the base of soil erosion, the outer driving stress (hydrogen erosion) apparently modified the outlook; 4. The fourth stage is of artificial controlling by human being. (2)Took the Shi-Wan-Xi small watershed as an example. The predicted amount of the soil erosion was 3893.38t/km2a, showing the medium degree which was far more than the allowed amount, granted by the hydraulic department of the nation for the mountain area made of soil and stone in south-west of China, which is 500t/km2-a. Whereas, the amount of the soil loss from the lope land had reached to 10826.54t/km2-a, which already got to the most degree and could be regarded as the source for the course of the soil erosion for the region. (3)The altitude height of the small watershed rose up from the infall field to the source field, appearing with plain land, hills and small mountains in turn, which led to apparent vertical distribution of weather, plantation and soil resources. So, mode of the dooryard economy, mode of sight-seeing agriculture and mode of coordinating forestry, bush with grass were proposed and built according to the altitude. (4)While, on the opposite of the stable economical development of the small watershed, the lack of advanced industrial chain, the shortage of agricultural input, the incomplete agricultural market, along with the low level of agricultural technology, would limit the developing speed of socialeconomy. So, measures aiming at improving the level of the agricultural industrialization, agricultural intensivism, the level of comprehensive and scientific agriculture, and lifting the income of the farmers should be recommended to accelerate the development of the small watershed.(2) The assessment of the sustainable utilization for the land resources in the three-gorge areaThe results from the research about the distribution of the soil resource, which based on the GIS technique, and took Shi-Wan-Xi small watershed as an example, showed that the area of land enlarged apparently with the raise of the slope. For example, the ideal agricultural area owned 18.54% when slope was lower than 15° , while 27.30% at 15° -25° , and the region mixing forest with stockbreeding region, where the utilization was very difficult, owned more than 50% when the slope was larger than 25 ° .Comparing the soil degradation index of the forestry, that index of the immature forest, uncultivated field, internal-tilling field, orange garden, infield on slope and paddy field were -10.09%, -18.37%, -5.73%, -6.52%, -8.46% and 2.79% respectively, which showed the change of degree of the soil degradation when the natural forest changed into agricultural use. The situation was the most serious in the uncultivated field, while the lightest in paddy field. The planting profession made up of the basic income of the economy of the small watershed, with the industry and other avocations followed behind, and the contribution of the forest and fruit industry to its economy was the smallest, based on data by analyzing the output with input. This was determined by the natural economic condition of the small watershed. The calculation with 23 items, according to the method of analyzing the main element and method of comprehensive assessment, showed that the field-utilizing index from 1996-2002 was -3.43, -1.96, -0.95, -0.2, 1.12, 2.22 and 2.79 respectively. The comprehensive administration, the increasing of the farmer income and the change of the land-utilized pattern has attributed to the increase of the field-utilizing index and the extent of the sustainable quality. The whole courses explained that the sustainable utilization could be strengthened if the economical development of the small watershed had been correctly conducted, and the potential resources of the watershed had been advanced enough, as well as the agricultural market had been regulated to transport the labors in many ways.(3 ) The supporting system for the decisions to administrate the small watershedThe building of the supporting system for administrating decisions to the mountain small watershed must adapt the methods of systematic analyze to design the structure and to show the system with the related parts in the model. The sequence of researching and developing this system should follow the listed arrangement: the first, build the factors base; the second, analyzing and assessing; the third, design the small watershed; the forth and last, decide the thinking for administrating the area in strategic, designing and operating ways. The software of GIS, ARC/INFO, Arcview, Mapinfo and Visual Foxpro6.0 were helpful to build the local factors' base of...