Study On 1-D Water Temperature Model Of River Unsteady Flow

Water temperature is an important factor of water quality. It is closely allied to other elements of water quality, such as COD and DO. And it also has a closer relationship with aquatic ecosystem. Based on the previous studies and combined the simultaneous observations and the experiments with numerical simulation, the algorithmic method is studied for water temperature of discharging flow of hydropower station under the function of incomes and expenses of heat. The accomplishment of this study will provide theoretical base for establishing operation plan of water for ecosystem and environmental impact assessment of catchments development. The main contents of the study and results are as following: 1. Based on the previous studies on unsteady flow of hydropower station, the simultaneous equations of Saint-Venant is predigested and the model adapting to one-dimensional unsteady flow of long river and long time is founded, which based on the Preissmann implicit identifier method. In addition, a method for calibrating general roughness coefficient is put forward by applying the model to the field data at different discharges. 2. According to the analysis of many factors that affect the water temperature of river, the water temperature model is established for forecasting downstream flow temperature gradient along the river. The model is validated to match the field data. The results indicate that the outputs of model are matching to the field data and the model can be applied to forecast water temperature of natural rivers and the downstream river reach of reservoirs. 3. The simultaneous observations were carried out on hydrology and water temperature of Daduhe river in the last ten-day of October. The results indicate that the water temperature of Daduhe river is increasing by degrees from upstream to downstream, the water temperature is allied to some factors of weather, and the water temperature of river reach is affected by the building of hydropower station on the river reach. According to the study on field observations, a law of water temperature's change along the river and an available empirical formula for calculating water temperature by using weather factors were put forward. 4. The model is applied to forecast the impacts of unsteady flow by the operation of Pubugou hydropower station on water temperature downstream the dam. The impacts of reservoir operation on entironment of downstream are analyzed. The results indicate that the water temperature increases with distance very slowly and the water temperature of downstream subjects to the temperature of discharging flow of reservoir. The Pubugou reservoir has less impact on entironment of downstream river reach.