| The dam is an important auxiliary tool for human to develop and manage water resources, which plays a positive role in flood control and waterlogging, refusing salt and impounding fresh water, irrigation and water supply, navigation and aquaculture, entertainment, ecological protection and so on. However, with dams being built, the continuity of natural stream is truncated, that leads to the velocity of flow slowing down, the runoff of river decreasing, the self-purification of water decreasing, and the aggravated water pollution. In recent years, the negative effect of dam construction has gradually highlighted, causing a series of problems like water pollution accidents, ecological and environment deterioration and biodiversity decrease. At present, the problem of river water resources development and management and the pressure of water pollution control in downstream caused by dam construction have taken the high attention of the government, leaders and experts. Therefore, the multi-phase transformation process of water quality and mechanism in the sluice-controlled river reaches are researched, the research of water environment evolution mechanism in the sluice-controlled river reaches and the efficacy assessment of sluice operation in water quality improvement are strengthened. And these have important practical application value for people to cognize the effect of dam in water resources development and protection objectively, decrease the risk of ecological and environment brought by hydraulic engineering building. In this paper, the multi-phase transformation process of water quality and mechanism are researched mainly from the following several aspects:(1) The mechanism of the multi-phase transformation of water quality in the sluice-controlled river reaches was summarized, and the whole frame of the multi-phase transformation driving pattern of water quality in water, suspended solids, sediment and alga(dissolved phase, suspended phase, sediment, biofacies) was put forward. Then the change characteristics of water environment in the sluice-controlled river reaches were discussed to analyze the leading role of sluice operation in a series reaction process of physical, chemical and biological.(2) The mathematical model of multi-phase transformation of water quality that considering driving force of sluice operation was developed. This model can not only reflect the spatial difference of hydrodynamic process in different areas of the sluice-controlled river reaches, but also reflect the transformation process of water quality in dissolved phase, suspended phase, sediment and biofacies through establishing mathematical expression which can describe the leading reaction process. These can provide means to simulate the process of multi-phase transformation of water quality in the sluice-controlled river reaches.(3) Simulating the hydrodynamic process in the sluice-controlled river reaches, and the kinetics process of water quality between different phases, such as migration, diffusion, adsorption, desorption, sedimentation, resuspension, intake, endogenous respiration, biochemical by application of the model to disclose the distribution relation of water quality in water, suspended solids, bottom sludge, algae under the effect of sluice control and the response process of sluice control. Then combined with the simultaneous monitoring data, the mathematical model was simulated and parameters were calibrated.(4) Through scenario analysis and numerical simulation, the space-time difference of pollutant distribution process under different scheduling system was recognized, and the driver effect of different scheduling systems for multi-phase transformation of water quality was assessed. In order to reveal the evolvement of water environment in the sluice-controlled river reaches, the contribution rate of sluice operation was computed, and the quantitative relation among water concentration, gate opening and the number of gate opening was built. |
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