Reseach On The Theory And Applicaton Of Flow-ecology Relationships In A Dam-river

China has the highest number of dams in the world.Dams effectively resist floods and droughts and also assist in irrigation and power generation,thereby contributing to enormous economic benefits and consequent social development.However,a large number of dams cut off the longitudinal connectivity of the river,alter the natural hydrological situation,and also trigger a series of issues,such as water ecosystem degradation,which conversely hinder the sustainable development of the economy.Maintaining the ecological flow of a dam_river is an effective method to resolve such issues.The process of determining an ecological flow involves quantification of ecological and human water use.It is necessary to coordinate stakeholders.Accurate assessment of the flow demand for healthy operation of aquatic ecosystems is the major barrier to this process.Specifically,effective ecological flows need to be explicit about flow-ecology relationships to adequately determine the amount and timing of water required.Building a flow-ecology response relationship is key to solving this difficult problem.This study selected a typical dam-river as example research object,analyzed hydrological alterations after the construction of the dam,identified the main disturbance factors for the near-natural hydrological situation,and performed macroinvertebrate animal quantitation based on the species structure and function of the aquatic ecosystem.The desired relationship and the hydrological threshold range were determined.An ecological flow desigjner method for the heavily disturbed section of the river was proposed.The main conclusions of the study were as follows:(1)Systematic analysis of the hydrological alteration of the river based on hydrological monitoring data of long sequencesBased on the data of DEM,river topography,and rainfall received by the area under study,a Wep-L distributed hydrological model was constructed,which reduced the natural flow data from the river before dams were built,and solved the issue of the lack of natural monitoring flow data in hydrological alteration assessment.Based on the flow data of the typical section after construction of the dam,variations between the characteristics of the flow period for the typical section before and after the dam construction were first evaluated.It was found that the flow period of the typical section was prolonged after the dam was built.Secondly,the innner and inter annual flows before and after the dam construction were compared.According to the variation characteristics,the dams increased the dispersion of the river flow and increased the risk of flow interruption.Finally,based on the IHA method and the revised RVA method,the monthly average,extreme value,extreme time,pulse frequency,and frequency of change were determined to quantitatively assess the changes in hydrological conditions after the construction of the dam.The results show that the dam caused significant disturbances in the flow components of the typical section of the main stream.Among them,1 daymin,3daymin,reversal rate,7daymin,and zero days were the main hydrological disturbance indicators for the main stream near the natural hydrological situation.(2)Based on the structural function of the freshwater ecosystem,the ecosystem status of macroinvertebrates in dam river was systematically analyzed and the key hydrological factors affecting the structural function of the macroinvertebrate animals were identifiedUsing a 2010-2018 long-term record of macroinvertebrate sampling data,the variation characteristics of macroinvertebrates in the study area were fully analyzed and combined with the three core ecological attributes that characterize changes in the macroinvertebrate community—the Functional Feeding Groups(FFGs),Habitats Trait Groups(HTGs),and diversity.Using the Ranking analysis and Network method,the hydrological factors with the highest correlation with the ecological properties of macroinvertebrate communities were identified:monmean,zerodays,ldaymax,90daymax,and 30daymin.Among them,FFGs were mainly affected by ldaymax,and HTGs were mainly affected by 30daymin.The diversity of macroinvertebrates were mainly affected by monmean.(3)Constructing a quantitative flow-ecology response relationship for macroinvertebrates in dam regulate riverThe core index of the macroinvertebrate community structure and the five most relevant key hydrological factors were fitted with a polynomial to produce a fitting effect hot spot map for the FFGs components and ldaymax,HTGs components and 30daymin,and diversity and monmean fitting.The effects were all better,and the response relationship for the FFGs components,HTGs components,diversity,and hydrological factors was constructed,and the specific response relationship for each component was quantified.For the FFGs component,with increase in ldaymax,due to matrix disturbance,food supply,and self-adaptability,the ratio of Filterers and Shredders first decreased and then increased,and the proportion of Gathers continued to decrease.Predators and Scrapers first showed an increase in the trend and then decreased.For HTGs,with increase in 30daymin,due to its morphological adjustment structure,substrate adaptability,and drift characteristics,the proportion of Clingers first decreased and then increased.The Burrowers ratio continued to decrease,and the Climbers ratio decreased temporarily.Further on,the proportion of Swimmers increased,and the proportion of Burrowers first increased and then decreased.The macroinvertebrate diversity index showed a trend of decreasing first and then increasing with increase in monmean.When monmean reached 30 m3/s,the boundary flow of the river species was dominated by the hydrodynamic species.(4)Based on the quantitative flow-ecology response relationship,an ecological flow designer method and guarantee technology for the heavy-disturbance dam-river are proposed.On the basis of the theory of Natural Flow Paradigm,based on the flow-ecology response relationship of macroinvertebrate quantification and combined with the characteristics of severe disturbance for the hydrological situation of the dam,starting from the ecological service of ecological demand and human social demand,a method for customizing the ecological flow of rivers that interfere with rivers was proposed.Taking the typical section of the dam river as an example,the multi-obj ective optimization method was used to quantify the ecological fiunction service provided by the river.Based on the flow data determined for the period after the 30-year-old sequence of monmtoring,the largest ecological function service so far was established.According to the problems encountered in the ecological flow management and guarantee process of Shaving River,an ecological flow guarantee mechanism for the gate-controlled rvers was constructed based on the adaptive management theory and water resources security measures.