Study Of Eco-environmental Water Requirement Of Zhangxi Drainage Basin In Ningbo City

People build water conservancy to meet the water need of the development ofeconomy and society, they often forget the water need of the ecosystem itself duringthe exploitation of water resources, then a lot of eco-environmental problems comeforth, such problems baffle the development of society. So this paper processes thestudy of the eco-environmental water requirement of zhangxi river. It combines thebase of water resource distribution, the health of ecosystem and thenature-socity-economy condition of zhangxi drainage basin in ningbo city toexpatiate the purpose and meaning of this paper. It looks back the domestic andinternational development courses and the achievements of the eco-environmentalwater requirement of rivers, analyzes the exsiting problems at present.A lot ofdetailed jobs have been done to investigate the nature-socity-economy condition ofzhangxi drainage basin.This paper begins with the intension of theeco-environmental water requirement of river, ecological ructions of river, analyzesthe influence factors of the ecological and environmental water requirements, thenfinds out the components of the eco-environmental water requirements of river. Thispaper associates the health of river ecosystem with the grades of the inner-riverecological water requirements, gets the corresponding result of the grade of waterrequirement based on the health appraisement of the ecosystem of zhangxi riverecosystem. This paper calculates the water requirements from two parts:one is theinner river, another is the outer river, it puts the emphasis on the hydraulics andhydrological calculation methods.then chooses Tennant method to calculate theecological water requirement of inner zhangxi river, chooses the most exhaustedflow method to calculate the environmental water requirement of inner zhangxiriver, chooses acreage rational method to calculate the ecological water requirementof outer zhangxi river. At last, quests for measures to guarantee theeco-environmental water requirement of zhangxi river from water quantity andquality, it gets the main results as follows:(l)The ecological and environmental functions of zhangxi river are maintaining the habitat of hydrophytes and aquatic animals, diluting pollutants and maintaining the stabilization of riverside system. There are many factors influence the eco-environmental water requirements of river, such as: the quality and quantity of water resources, the ability of water self clean, the exploitation of water resources and the health condition of the zhangxi river ecosystem, modes and speed of the development of society and economy, the aim of the management of water resources.the eco-environmental water requirements of zhangxi river are compose of the inner river ecological water requirement which maintains the habitat of hydrophytes and aquatic animals, the inner river environmental water requirement which keeps the ability of diluting pollutants, the outer river water requirement to satisfy the residents, enterprises, crops and greenbelt.(2)The result of the ecological water requirement of inner river is 0.922m /s, the environmental water requirement of inner river is 0.47m3/s, so the eco-environmental water requirement of inner river is 0.922m /s due to the compatibility and maximum principle. On April to Octorber, the crop ecological water requirement of outer river is 0.109, 0.144, 0.265, 0.395, 0.361, 0.251, 0.139m3/s respectively, the greenbelt ecological water requirement of outer river is 0.006m3/s, the water requirement of residents and enterprise along the river is 0.049 m3/s. So the eco-environmental water requirement of zhangxi drainage basin on November to March is 0.977m3/s, the eco-environmental water requirement of zhangxi drainage basin on April to Octorber is 1.092, 1.127, 1.248, 1.378, 1.344. 1.234, 1.122m3/s respectively, which accounts for 10.6% to 14.9% of Mean annual runoff amount of zhangxi river.the results are validated by one-dimension water quality model, it is illuminated that the results can meet the requirement of water environmental management and maintain the health of zhangxi river ecosystem.(3)Analyzes the guarantee measures of eco-environmental water requirement of zhangxi river from two aspects:the quality and quantity of water. The quantity of the eco-environmental water requirement will be meet by united attempering of jiaokou reservoir and zhougongzhai reservoir, by saving water and reducing pollutants . Thequality of the eco-environmental water requirement will be meet by three measures: the protection of the waterhead of two reservoirs and zhangxi river, the adjusting of industrial structure of the twons in zhangxi drainage basin, and the renovation ofzhangxi drainage basin.