| As a kind of renewable and clean energy, water resource is indispensable to the development of human’s society when the petrochemical resources are running short gradually. By the construction and operation of water conservancy projects, human activities have affected the natural flow process, which realize the transition of natural runoff energy and the redistribution of resources. Hydropower projects hold a significant position in exploitation and utilization of the water resources, which are playing huge economic and social benefits such as flood control, power generation, navigation and irrigation. Due to the fragmentation of watercourse and drastic alterations of spatial and temporal distribution to natural flow regimes caused by construction and operation of reservoirs, the aquatic and riparian ecosystems along the rivers are indeed adversely affected, such as eutrophication, decline in biodiversity, wetlands degradation and so on. With the rise of recent ecological problems and the strength of protection consciousness of ecosystem, how to alleviate the adverse effect on the ecological system by adjusting the reservoir operation has become a hot topic in the field of the reservoir scheduling. At present, our country has the highest number of dams in the world. The large-scale hydroelectric construction caused serious and even irreversible damage on river ecosystem. The traditional scheduling concept whose core is to maximize the economic benefit cannot already adapt to the engineering requirements of protection and restoration of river eco-environment. In addition, our country started late on research and practice of ecological operation. Hence, there is a pressing need to study and develop the theory and method of ecological operation which are in accordance with our situation. In this thesis, we focus on the main ecological problems, and study the reservoir ecological operation by using eco-hydrology, eco-hydraulics and modeling methods of complex system with the goal of improving and restoring riverine ecosystem. The main content of the innovation and contribution in this thesis are listed as follows.(1) Considering the limitations of existing physical habitat models that can only be used in the rivers that have complete ecological monitoring data, we establish physical habitat models based on Mamdani fuzzy inference system and adaptive neuro-fuzzy inference system. Based on precise flow field simulation results, the proposed fuzzy habitat models linked these data to the expert knowledge base to compute habitat suitability indexes of each unit by using fuzzy logic reasoning. At last, the weighted usable area and highly suitable proportion of habitat at different river discharges were calculated to study the ecological water requirement. To verify the proposed models’validity and reliability, Chinese sturgeon spawning habitat on the downstream of the Gezhouba Dam was simulated. By comparing the simulation results to the field-measured data, the proposed methods which are weak dependence on monitoring data by considering expert knowledge and experience are feasible and available. This research could be helpful to ecological protection and river management for the rivers which are lack of field-measured data, and could also provide a reference for the application of fuzzy mathematics in water ecology.(2) Based on the impact from water conservancy projects on natural runoff process as a focal point, the effects of the Three Gorges cascaded reservoirs on eco-hydrological characteristics were analyzed by using Indicators of Hydrologic Alteration, Range of Variability Approach, Mann-Kendall method and R/S method. Moreover, using eco-hydraulics indicators to evaluate the impact of water conservancy projects on riverine ecosystem was proposed. By using the proposed method, the effect of the Three Gorges reservoir impoundment on spawning habitat suitability of Chinese sturgeon in Yangtze River was assessed, and it can provide theoretical and data support for the implementation of reservoir ecological operation.(3) Aiming at the demand of the improvement and restoration of riverine ecosystem in the middle reach of Yangtze River, a multi-objective optimization model of reservoir ecological operation which can consider various ecological flows was proposed. In this study, taking1-month as time interval,1year as dispatching period, considering the ecological water requirements of ecosystem, reproduction of the four major Chinese carps, Chinese sturgeon propagation, saline water intrusion at the Yangtze estuary and dissolved gas supersaturation, the multi-objective optimization model, comprised two objective functions that are to maximize the total power generation of the Three Gorges cascade during the course of the dispatching period and to release water from the Three Gorges reservoir in a manner that as far as possible to meet the demands of ecological water requirement was established. Afterwards, the NSGA Ⅱ was applied to solve the proposed multi-objective model, and the reasonable results were obtained.(4) There are numerous methods for calculating ecological water requirements. According to different objects and goals, the different ecological flows can be obtained. Due to the particularity and complexity of ecosystems, the ecological flow can hardly validate by experiments. Furthermore, the relation between instream flow and riverine ecosystem health is nonlinear. Considering these problems, the multi-objective ecological operation model based on similarity measure between vague sets was established. In this model, the bound of suitable ecological flow was defined as a range, and various ecological flows obtained form different targets can be integrated. To quantify the ecological objective, we used vague sets to describle the degree that the releasing discharge from the reservoir closes to the ideal ecological flow. By ascertaining the similarity between the previous vague sets and the ideal vauges sets, the ecological objective was obtained. The Three Gorges cascaded reservoirs were used as a case study in this paper. The proposed model could not only enrich the modeling methods for reservoir ecological operation, but also expands the application of fuzzy mathematics in the field of reservoir ecological operation. |
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