Study On The Adaptive Management Of The Downstream Reservoir Based On The Eco-hydrology Responding Mechanism

The river is the basis of human survival and development. With the accelerating development of hydropower, society and economy, the ecological environment for river corridor in dam downstream has been becoming bad to worse. So it is the focus problem of river management and protection in order to keep the structure and function of river corridor are much better. In view of the great complexity and uncertainty of dam downstream river corridor ecosystem, including the river ecosystem, riverine or estuarine wetland ecosystem and coastal system, ecosystem types diversity, as well as the limitations of human knowledge, the reservoir downstream ecological adaptive management mode based on the eco-hydrological response mechanisms was proposed, which had some breakthroughs in management style, system, objective and approach compared with the traditional models. Additionally, it allowed the comparing with a variety of theories, techniques and measures, and then based on the combining with a new understanding, information feedback and the latest advancing technology, the original reservoir operation mode and eco-environmental protection programs was improved. Reservoir downstream ecological adaptive management based on the eco-hydrological response mechanism begins from the scientific recognition of the quantitative relationship between Ecology and hydrology factors, and by the constraints of the available water resources, and then put forward the best management options about reservoir regulation. It is important to provide not only technical support for the harmonious development between hydropower development and ecological environment protection, but also an important reference for domestic reservoir ecological adaptive management. The main researches are as follows:1. The systematical elaboration of the theoretical basises of the reservoir ecological adaptive managementThe theoretical basis includes the theories of sustainable development, ecosystem ecology,"natural-artificial" dualistic water cycle. Hydrological conditions is the most fundamental driving force for the changes of the river corridor ecosystem, however, the water resources development and utilization is growing with the high intensity human activities, and the relationships between rivers, lakes and groundwater storage are changing, and also the conversion path between the surface water and groundwater, and then forming of "water intaking-water using-water consuming-water drainge" has come into being. The natural water cycle and artificial collateral shift in the water cycle, ecological factors are changing associated with changes in water cycle process. Therefore, the eco-hydrological process analysis is the basis about the ecological adaptive management of the reservoir downstream, the research of environment flow process is the focus of management based on the ecological protection objectives, the improving of reservoir management is the guarantee of the management.2. The scientific connotation of reservoir project ecological adaptive managementEcological adaptive management for the reservoir project is "the best mode for adaptive management, aiming at the complexity and uncertainty of the river corridor ecosystem and limitations of human cognition,based on the study on Ecological-Hydrological Response Mechanism,adhering to the principles of sustainability, adaptability, feedback, scientific and controllability, following the law of coordinate development for natural environment and social economic,by taking the consult and communication among relevant stakeholders as its premise,and achieving the goal that benign development of reservoir ecological environment and social economic within the affected areas,and using the means of persistent monitoring, scientific quantitative assessment, feedback mechanism, maintains sustainable and healthy development of the reservoir ecosystem, downstream river ecosystems, river/estuary wetland ecosystems and the coast domain ecosystem. Adaptive management is the innovative management mode which faces the complexity and uncertainty of the river corridor ecosystem and limitations of human cognition, highlights the "learn" and "adapt" supporting by actual data and actualizes dynamic, flexible and standard management.3. The theory and methodology of reservoir ecological adaptive management adapting to the Chinese contextBased on a closed reservoir ecological adaptive management, determining target-building decision management solutions-implementing-monitoring-evaluating-adjusting ", the assessing method with three dimension, a system and an assessment was built up (The three dimension is Eco-hydrological response mechanism, three conditions constraint, ecosystem structure and the regulatory function dimension; one system is the long-term ecological monitoring system; an assessment is the adaption assessment for management effect). The specific contents as follow:(1) the eco-hydrological response mechanism was determined by the hydrological processes, landscape scale and river scales, and the ecological-Hydrodynamic contact, based on the sensitive ecological objectives, was established using the methods of1HA ecological flow component indicator, the RVA, landscape pattern analysis and hydrodynamic model;(2) the adaptive management objectives was determined through the reservoir downstream ecosystem, river or estuary wetland ecosystem, coast domain ecosystem and critical eco-hydrology processes at critical period.(3) the adaptive management plan was established according the condition of water resources availability, ecosystem healthy cycle and economic society to be better;(4) based on the long-term ecological monitoring system, the implementation management was carried out to provide basic data for the management effective evaluation;(5) the adaption of sensitive elements on ecological environment was assessed from the natural resources and ecological environment;(6) the feedback was proposed with regulatory guidelines of ecosystem structure and function, combining the results of management effective.4. The applications about adaptive management of reservoir downstream based on eco-hydrological responsding mechanismThe theory and methodology of adaptive management of reservoir downstream based on eco-hydrological responsding mechanism were applied in Xiaolangdi Reservoir. The results are as follows:(1) The changing degree of environment flows and the corresponding ecological effects were analysised based on the Hydrological processes. The overall changing degrees of Huayunkou, Gaocun Lijin stations were separately0.85,0.73,0.77, which were based on the comparison of after the construction of Xiaolangdi Reservoir and the natural period of river; and meanwhile they were separately0.54,0.79,0.66, which were based on the comparison of before and after the construction of Xiaolangdi Reservoir. According to the current managing mode, low flow was greatly reduced especially the extreme low-flow, but it could ensure the ecological functions of the low-flow; high flows frequency was closing to the natural period, while the increasing of duration and the reduction of peak flow resulted in not yet function; small floods improved the function of sediment transferring of downstream, but it can not furnish supplies to the flood plain; and the frequency of floodplain floods was reducing.(2) Based on the analysis of changes in the physical, chemical and biological characteristics of fish habitat, the links between fish growth and reproduction and hydrological factors were studied. According to the current managing mode, the main channel flow capacity was increased to4000m3/s; water quality could meet the water quality standards Ⅲ; Water and sediment regulation regulation have a negative impact on aquatic biological resources, and the biomass was the lowest in the year. With the Longitudinal time scale, Fish resources has continued to decline (the fish resources of the1950s and1960s were in the most abundant), sediment and water quality wert the restricting factors during the fish growth and reproduction time, but the hydrological factors is the most important constraints; the water and sediment regulation led to the high consentration of silt, the reduction of dissolved oxygen, and in2010-2011the types and material resources of the two germplasm resources protection areas were reduced with42.9%-84.7%,47.0%-61.1%seprately. In view of all the analysis, the stable natural river runoff is the most appropriate for the growth and reproduction of aquatic organisms including the fishes.(3) Based on the quantitative analysis results of the birds, it could be analysised from the landscape and hydrological driving force. The number of birds and species diversity has increased to some extent, and some traveling birds were beginning to stay in here for reproduction. Based on the analysis of the landscape driving force, the degree of fragmentation were increasing, the important habitats of birds are shrinking, and the natural wetland were reduing with the increasing of the artificial wetland; the water recharging of riverine wetlands may be happened when the runoff where the river is more than7014m3/s, in view of the downstream flood control the water charging mainly depends on the rainfall and the lateral seepage recharge of groundwater; due to the control of the gate, estuarine wetland mainly depends on the artificial recharge, but now the artificial fill water resourses is far from the water demands of the Delta by the0.35billion m3.(4)The comprehensive evaluation of the current managing model scored2.3097, the ecosystem function was in the lower-middle. Based on the adjustment and feedback mechanisms, the adaptive management objectives and eco-hydrological process management solutions were put forword, as follows:The minimum annual ecological runoff of Huayunkou, Gaocun and Lijin are15.45billion m3,13.83billion m3and7.68billion m3separately, the medium are21.57billion m3,18.21billion m3and9.46billion m3, the most suitable are26.57billion m3,21.99billion m3and11.56billion m3; during the water and sediment regulantion, the minimum monthly runoff in June of Huayunkou, Gaocun and Lijin are separately1300m3/s,967m3/s and798m3/s, the medium are1570m3/s,1275m3/s and1088m3/s, the suitable are1743m3/s,1389m3/s and1231m3/s; the minimum in July are815m3/s,751m3/s and892m3/s, the medium are984m3/s,983m3/s and1215m3/s, the most suitable are1093m3/s,1071m3/s and1376m3/s. Compared with the History periods, the non-flood season could recovery to the state of1969-1987period; in the flood season, the Minimum, Medium and suitable ecological flow process could approach the ecological flow standard of1969-1987period as well, good, very good; Due to the water and sediment regulation, the runoff in June and July were undergoning great changes, and they all have reached the largest and the best state of the ecological flow standard; and it need to adjust the flow rise rate and fall rate in the time of water and sediment regulation, in order to mitigate the adverse impact to aquatic organisms.