Study On Drainage System And Management For Mountainous Towns In Three Gorges Reservoir Region

Following the China's West Leap Project, the quantity and economic level of many small mountainous towns in Three Gorges Reservoir Region increased rapidly in the recent years. However, some technical issues troubled these towns when they are in their preparation of construction and operation management in drainage facilities more or less. Some designers can not comprehensively consider all factors in designing, so that they choose the wrong drainage system. According to the current situation of these towns in Three Gorges Reservoir Region, in order to promote the healthy development of these towns, It is necessary to make sure the appropriate drainage system and the corresponding drainage pipelines'management measures according to the specific circumstances of these mountainous towns.Firstly, several drainage systems which have wide applications are reviewed, also including their advantages and disadvantages. By establishing mathematical models, pollution load of early-stage rainfall in separate system and combined system overflows are comparatively analyzed when pollutant concentration (CODcr) in early-stage rainfalls are respectively in high value, median and low value. The conclusion is that in the towns which have well environmental conditions and drainage systems management, separate system is better because the concentration of pollutant in early-stage rainfall is less. Conversely, combined system has more advantages.Comprehensive evaluation index system of drainage system of mountainous towns in Three Gorges Reservoir Region was established through Literature Searching,Structured Interview and Delphi. The weight of the index system was determined by linking with M-AHP and Entropy Method. Through the analysis and comparison of common comprehensive assessment theories, Grey Related Analysis was used to evaluate the drainage system of mountainous towns in Three Gorges Reservoir Region. The conclusion is that correlation of incomplete separate system is the highest, followed by the complete separate system and interceptive combined system.Considering the present situation and characteristics of mountainous towns in Three Gorges Reservoir Region and comprehensive evaluation results, different drainage systems which are suitable for the different types of mountainous towns in their different development stages were put forward. For the new towns and those towns who have potential for development or have better surface environment and air quality, interceptive separate system can be constructed step by step on the basis of financial capability: firstly build sewage pipelines, then separate system, and finally forms into interceptive separate drainage system. But for those old district and towns whose surface environment is not so well, construction land is insufficiency and development is restricted, interceptive combined system is relatively more appropriate. Build partial wastewater treatment at the intercepting well to treat the overflows or take same measures to reduce water quantity at sources and in the pipelines to cut the water pollution when there is adequate fund.Finally, aim at solving the misconnection of separate drainage system and combined drainage system overflows, a set of management methods and measures were put forward for the mountain towns in Three Gorges Reservoir Region.