| Eco-environment is not only the basic of the material production activities, but also fundamental to the survival of mankind's basic conditions. It is restricted by natural laws of the development constraints, as well as human socio-economic activities.To protect and improve the Eco-environment has become one of two equally important themes which is "environment and development" and "peace and development" in the 21st century international community.it is an important way to achieve sustainable development.Eco-environment of China is relatively fragile.economical development based on predatory exploitation of ecological resources and the occupier of Eco-environmental water demand. It has caused the quality of environment deteriorating day by day and the service function of Eco-environment aggravating.Because of the shortage of water resources, The water used in agriculture is occupied by the consumption of daily life and industury and the Eco-environmental Water use is occupied by agriculture's in the development of socio-economic. This kind of issue caused deterioration of the eco-environment. In order to protece eco-environment, to strengthen its service functions for the human society, the water resources should be unified managed and rationally distributed to ensure the eco-environmental water demand. So in arid, semi-arid, and other fragile eco-environmental areas, eco-environmental water with proper quantity and quality would be particularly important.The actuality and evolvement of Eco-environmental water at home and abroad was systemic dissertated ,the concept and calculational model was studied in the thesis. In my opinion, eco-environmental water demand is the combination of eco-environmental water demand quantity, quality and spatial-temporal distribution. The pollution of the environment deteriorate,especially water pollution. Researches just on the quantity of the eco-environmental water demand can not meet the actual needs.The study objece of eco-environmental water demand is ecosystem.The method and calculation model should start with its nature character. the necessary ecological parameter should be taken into account besides the the hydraulics parameter in the computational method. The computed result varied infinitely if the hydraulics parameters are used only when a identical object is studied. The results are different from each other and involve no reference value. We begin the study with the eco-environment itself and calculate the quantity of eco-environment water demand by period of time. The result is more close to the true value.In the model, we divide eco-environmental water demand into three parts as the eco-environmental water demand for land, rivers, and wetland(swamp and lake). Water quality is broght in the model by the water quantity for dilution of the contamination. By means of calculating the quantity of the eco-environmental water demand in different periods, spatial -temporal distributing also be taken in.In the thesis, The west region of Jilin Province is selected as study area. It includes Baicheng city, Songyuan city and 10 other counties. Years for the average rainfall in this area is 429.5 mm and the average amount of evaporation for years is 1621.7 mm. It pertains to arid or semi-arid climate. Rainfall here is no more than the 1/3 of Jilin province's average level. Fresh water in this area is inadequate. According to the Eco-environment condition appraisal technology standard (Trial) (HJ/T192-2006) ,the study area is assessed. we can conclude: the eco-environmental Index of west region of Jilin Province is 39.96. The indexes of Baicheng and Songyuan are 39.63 and 41.10, with reference to eco-environmental conditions classification standard , It belong to ordinary level.That is to say,the vegetation coverage is medium and life-form diversity belong to general classification.Though it is relatively suitable for human, there are conditional factors which are not suitable. With reference to water density index, The two cities are 9.08 and 8.46 which are far below the average index of the Jilin province. Lack of water resource and increasing quantity of water used for industry and agriculture caused the eco-environmental water use in western region of Jilin Provine decease greatly. Furthermore, it is also one of the reasons why the quality of eco-environment conditions is comparatively low.According to the results calculated by remote sensing of western region of Jilin Province, the eco-environment water demand in this area is 226.77 ~ 517.03×108m3. The water resource which can be used is just 237.57×108m3. It also includes the water which is used for living,industry and agriculture,and the quantity above is 63.53×108m3.The eco-environment water use is just 174.04×108m3. Compare with the smallest eco-environment water demand, the quantity of inadequate water is at least lack of 52.73×108 m3. If we do not take the water used for the contamination dilution into account, the eco-environment water demand for reviers can decrease by 13.36×108m3 which accounts for 25.34 % of the inadequate water.In conclusion, we should give emphasis to the water used for the dilution of contamination.The large-scale rivers in western region of Jilin Province include Songhua River, Nenjiang River, Lalin River, Huolinhe and Taoer River. Over 700 lakes are widely spreaded in the region. The Dalai Hydrometric Station of Nenjiang reveals that the average annual runoff volume is 2.18×1010m3 for many years, the runoff of Songhua River through the western region is over 1.00×1010m3, but the utilization rate is just about 2% of the runoff which result the situation"no water to drink by the well", Effective freshwater resources is not inadequate in western region of Jilin Province. Adopting various projects measures to improve the utilization rate of surface water resources is the key to resolve the shortage of eco-environmental water demand. According to the planning standards of eco-environment construction from "The Environmental Protection Outline of the Eleventh Five-Year Plan of Jilin Province" and "Ecological province of Jilin Province of the overall planning framework",we forecast the eco-environment water demand and use of western Jilin Province from 2010 to 2030,which shows that: from 2010 to 2030, forecast once every five years, and the inadequate quantity of eco-environment water demand is:64.36×108m3, 60.3×108m3, 60.51×108m3, 72.92×108m3, 75.64×108m3.It reveals that the trend is gradually increasing. The inadequate of the eco-environment water demand which is the main factor is still plagued the quality of eco-environment to improve in western region of Jlin Province.Finally, aiming at the shortage of the Eco-environmental water demand in West region of Jilin Province and the current situation of water resource, some improvement steps and advice of environmental management and Engineering technology are put forward.The problem of the Eco-environmental water demand inadequate is the result of both the human society and environment's demand for water resource. Eco-environment is the basic of human's development. Properly coordinating the relations among the water demand for living, producing and eco-environment is the key to the water inadequate. Allocate water resource rationally, see eco-environment water demand as cell and integrate it into the human economy development, can make human society and eco-environment succeed achieving sustainable development.
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