A Study Based On Priority Of Watershed For Synthetical Evaluation

A Study Based on Priority of Watershed for Synthetical Evaluation , this paper chooses the Meijiang river Watershed which is the headstream of the Ganjiang river in Poyang Lake Watershed as the research area, to divide the Watershed into 23 sub-basins and give them serial numbers according to DEM and river net.The altitude , gradient , the density of the river, erode degree, the density of the population, ecological value, the density of the road, vegetation's covering degree and patch density, LPI, CONTAG index are included in the index system.To start with three visual angles , i.e. the natural conditions of the basins , the influence brought by human activities and the basic state of the basics. The influence brought by both human activities and the natural conditions can be reflected through the result of the research.To make use of the EMDS(Ecologic Manage Decision System)on the ARCGIS and the priority analysis in the Watershed synthetical evaluation, this paper tries to assess the status quo of the basin entironment. According to the model's parameter and condition, firstly, to establish the knowledge base which is helpful for the assessment on the basin entironment in NETWEAVER, to introduce into fuzzy logic, to standardize the detail data of different indexes in NETWEAVER ; secondly , to reflect the index structure by the use of CDP(Criterium DecisionPlus), then to link with the space data-base and calculate the priority. By this way , we can get the data including the priority of index, natural condition, human activity, the basin state and basin synthetical priority.According to the result above, this paper draws distributing space and uses five grades: best, better, so-so, worse and worst to reflect the distributing state of the indexes and synthetical priority. The result indicates that sub-basin 13&14 has the highest priority of natural condition in the Meijiang river, sub-basin 5,9,15,22 and 23 has the higher one; Sub-basin 1,2,4,7,8 and 20 is allocated in other level. The basins with better natural condition mainly distribute in the areas where the topography is flat, the altitude is low, and this is the reason why these areas can absorb population and have higher economic develppment level.From the priority analysis of human activity, we can find out that the priority degree of the regions along the river and high-way where the economic activity is frequent is high. Although the ecological value of these sub-basin is low, proper road density and population density make the priority high totally. Such as sub-basin 9, 10, 13, the priority is"best"; whereas sub-basin 1 and 4 behaves bad because of the bad basin management and protection.From the analysis of basin state, it is easy to find that three regions'priority is low , the first group of 5, 9, 13, 15, the second group of 10, 11 and the third group of 21, 23. All the basins above locate the joint of Meijiang river and the exit; the others is high .The priority of sub-basin 1,2,4 and 6 is the lowest, the majority is"worst"or"worse". They mainly distribute in the north of Meijiang river. Because of the varied topography, the high altitude, small density of population and poor transpotation, the synthetical priority has the strenth in the whole Meijiang river; the priority of the sub-basin 9,13,14,15,18,19,21 and 22 is in the level of"better", they are also the distribution region with high priority, and they mainly distribute in the south-western. Because the topography is flat, the altitude is low, it is the confluence of rivers, the traffic area and the population concentrated area; whereas the priority of the sub-basin 7,8,11,12,16,17 and 20 which lie in the east and south-estern area is in the level of"so-so", in other words,it is between the priority of these regions.