| Liuxihe Reservoir, a large reservoir located in Guangzhou, is the major water source supplying drinking for Guangzhou city. Based on the investigations from 2001 to 2002, its average trophic state index was 33.8, which indicating a mesotrophic reservoir. For understanding the reservoir hydrodynamics and ecology in deep, a two-dimensional, laterally averaged hydrodynamic and water-quality model, CE-QUAL-W2, was applied to the reservoir. Water level, temperature distribution, dissolved oxygen, algal biomass and nutrient were simulated by the model. The model was calibrated using hydrodynamic and water-quality data obtained from April 2001 to December 2002. The calibration results showed the model was good at simulating the hydrodynamic and water-quality characteristics of Liuxihe Reservoir. Simulated water level, temperature, dissolved oxygen concentration, nutrient concentration and algal biomass were fit well to the measurements. A hypothetical input of phosphate at the upper rivers of Liuxihe Reservoir during a major storm event took nearly 102 hours to disperse over the entire length of the reservoir. Simulations of algal response to increases of nitrogen and phosphorus loads demonstrated that the algal growth was limited by phosphorus in the reservoir. The model was also used to evaluate the effects of increasing tourists in the nearby forest park on the water quality of surface layer within the dam reach. The results showed that both phosphorus concentration and algal biomass increased significantly. The influences of pollutants by tourism were more obvious when both inflow and water level of the reservoir were low. Effects of changes in reservoir outlet elevation on the vertical profiles of water temperature and dissolved oxygen concentration were simulated. The deep outlet could increase the depth of water temperature thermocline. It could also reduce the anaerobic extent of reservoir bottom.
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