Theory And Engineering Application On Water Demand For Ecological Environment Of A River System

Human are suffering from execrable environmental problems. The water demand for ecological environment of a river system is a new concept, which is put forward in recent years aiming at protecting and scientifically restoring or improving ecological environment in the process of exploiting and utilizing water resources. It has become an impending problem that how, on the base of limited gross water resources, by controlling the human activities in the allowable range of ecology, resource and environment, to realize the reasonable collocation of water resource, to sustain the water demand for ecological environment and eventually to meet the need of economy's sustainable development and water resource's sustainable usage and ecology balance. However, so far, there are no definite accepted definition, uniform calculation theory, criterion and methods. Different experts and researchers use different research approaches. The phenomenon brings inconvenience to the practical management and operation.In this thesis, on the base of the correlative documents, the background and significance of water demand for ecological environment were analyzed, the emergence and progress of it were expatiated, and the existing problems and difficulties in that domain were summarized. Under the guideline of ecology system and sustainable development, from the aspect of river ecological environment, for the purpose of realizing the harmony of society, nature and economy by sustaining and harmonizing the system function of a river system, a new way to compute the water quantity demanded by ecological environment is brought forth. Next, the concept was reviewed, the characteristic and influencing factors were analyzed; the constitution and research range were confirmed. By analyzing the coupling relationsof all the subentries of water demand, the theoretic computation algorithm can be obtained.On the basis of the confirmation of water demand quantity for ecological environment, the approaches are discussed. It is studied from five dimensions, including spatial-temporal and structure. Different computation approaches are summarized and introduced, including their theories, characteristics, applicable range, formulae and precision. Then, it is introduced how to revise the model to fit the nature condition and improve the precision and eventually the assessment system is built.By using Zagunao river basin as an example, the impact of the stepped exploitation of Zagunao river basin on river system functions was evaluated by combining with the protective policies and targets for local ecological protection and analyzing the system functions of the river was reviewed. The allocation and characteristics of the Za Gunao river basin were reviewed. The last step is to choose appropriate model for each subentry of water demand and revise the parameter or criterion according to local natural condition. The minimum water demand for ecological environment of Xuecheng section of Zagunao River was analyzed and computed. The thesis provides the guidelines for rating collocation of the water demand for local ecological environment and ensuring the sustainable development of the river basin.In summary, the further development and improvement on water demand for ecological environment of river basin is prospected: it needs participation and cooperation by multi-domains experts; the aquatic-creatures' requirements to hydraulics condition need the further observation and study; the relationships among the river system functions and the dynamic character of water demand on ecological environment should be considered; how to prove the reliability and improve the precision of the computation; and how to operate and maintain the water-allocation according to computed water demand.