Effects of dam reconstruction on thermal-ice regime of Fengman Reservoir

A laterally-averaged 2D water temperature model coupled with an ice cover module was used to investigate the influences of the Fengman Dam reconstruction on its thermal regime. Variations of the thermal-ice regime and outflow temperature under typical hydro-metrological conditions were simulated and validated with field data. Due to the partial dismantling of the old dam after the reconstruction, the intake water is primarily taken from the surface layer of the reservoir. As a result, the total heat storage of the reservoir throughout the year and the outflow temperature from January to March will decrease. Furthermore, the low outflow temperature in the winter will result in a decline of the downstream water temperature and negatively impact the rime scenery near Jilin City. In order to increase the outflow temperature in winter, an operation scheme that combined the new intake with the old intake of the III-phase project of old dam was discussed. The results indicated that this scheme could increase the outflow temperature to ensure a 70 km open channel in the downstream river in a typical winter, and eliminated the negative effects on the rime scenery.