Ecological And Environmental Water Demand Of Macro-tidal Estuaries And Its Implementation Measures

Taking Qiantang Estuary for example, this paper systemically studies the calculation methods and realization measures of ecological and environmental water demand of macro-tidal estuary.The estuarine ecological and environmental water demand is the critical water quantity related to certain time and space regards to given ecological protection, restoration and construction objectives, including water demand for the balance of sediment transport, water demand for balance of salinity, water demand for dilution of pollutant loads to satisfy the water quality requirement and minimum ecological water demand. Combing the connation of estuarine ecological and environmental water demand, this paper sums up its basic properties as temporal, spatial, uncertain, and consistent of water quality and quantity. Decision of quantitative results of the water demand should be according to river reach attribute, periodic attribute, function analysis function priority analysis, full reach optimization and compatibility.Relationship among estuarine erosion or deposition river volume, periodic mean runoff and initial river volume of Qitang Estuary is build up based on observed underwater topographical datum with the complementary datum calculated by one dimension movable-bed model. Taking allowable river deposition value as the control target, the water demand for the balance of sediment transport is gotten, and the requirement is no less than 80 percent of the natural runoff, requirements of wet season and dry season are estimated meanwhile. As the objective to protect water intake conditions of domestic water consume of Hangzhou City, the water demand for resisting saltwater intrusion is 290～350m~3/s currently, and up to 425～500m~3/s in planning year 2020 regards to different river conditions. Environmental water demand of the river reach from Fuchunjiang power plant to Wenjiayan is up to 200～300m~3/s considering spring and neap tide based on planning sewerage discharge; Water quality down reach of Zhakou is controlled by tidal runoff. Minimum ecological water demand is 150 m~3/s based on hydrological analysis method.Integrated estuarine ecological and environmental water demand is gotten based on the result of the different parts according to the periodic attribute and compatibility deciding principles. Combined with the prediction of water requirement of the estuarine district, water supply and demand balance analysis is carried out, and the water shortage of Qiantang estuary under different class in different season is disclosed.Finally, the realization measures of estuarine ecological and environmental water demand are researched. In order to solve or mitigate the incompatibility between human water demand and ecosystem water demand process, some measures are discussed in this paper including adjust the present water intake location, enhance the water regulation function of Xin'an reservoir, establish water intake schedule of the estuarine users and reinforce the protection of the estuarine freshwater.