Hydro‐thermal modelling of the potential impacts of reservoirs on water temperature and incubation time of Atlantic salmon and brook trout in the Tobique River, Canada

Water temperature is recognised as a crucial variable in lotic ecosystems affecting the metabolism of aquatic organisms, with extremely high‐temperature events increasing the risk of mortality of various species. Impounding rivers to regulate flow and generate electricity is one of the causes of altered thermal regimes in river systems. This paper presents the results of a study to simulate the impact of reservoirs on downstream temperatures of the Tobique River, New Brunswick, Canada. CEQUEAU, a hydrological and water temperature model, was used to simulate and assess the flow and water temperature of the Tobique River from 1997 to 2020. It was coupled to a statistical model to generate water temperature at different depths in the reservoir. Results show that the CEQUEAU model was successfully calibrated for water temperature with an overall root mean square error of 1.7°C. Based on the results, when water is drawn from the lower parts of the reservoir, the mean water temperature downstream of the dam increases in winter and spring by ~1°C. The results of this paper provide insight into how dams can affect the incubation time of cold‐water species in eastern Canada. We calculated the hatching degree days of Atlantic salmon and Brook trout to evaluate the impact of dams on fry emergence. Results indicated that the hatching period of Atlantic salmon and Brook trout downstream of reservoirs may shorten under the influence of dams.