Abstract
Water temperature is a key physical habitat determinant in lotic ecosystems as it influences many physical, chemical and biological properties of rivers. Hence, a good understanding of the thermal regime of rivers is essential for effective management of water and fisheries resources. This study deals with the modeling of hourly stream water temperature using the equilibrium temperature model. This water temperature model was applied on two thermally different watercourses, namely, the Little Southwest Miramichi River (LSWM) and Catamaran Brook (CatBk; New Brunswick). The equilibrium temperature model is a simplified version of a deterministic model. As such, in the equilibrium temperature model the total heat flux at the surface is assumed proportional to the difference between the water temperature and an equilibrium temperature. In the present study, the equilibrium temperature was assumed to vary linearly with hourly air temperature. This study showed that there was a good relationship between the equilibrium and air temperature at the hourly time scale. The root-mean-square error (RMSE) obtained with the hourly equilibrium tem- perature model was similar to results reported in previous studies with values of 1.05˚C (CatBk) and 1.36˚C (LSWM). The model's performance was best in late summer and autumn when water levels were low. In contrast, the presence of snowmelt in the spring resulted in poorer performances. This study also showed good results in estimating the daily mean (Tmean) and maximum (Tmax) wa- ter temperatures from the predicted hourly water temperatures, which were often required in fi- shery management.
Highlights
Water temperature has both economic and ecological significance when considering issues such as water quality and biotic conditions in rivers [1]
In Catamaran Brook (CatBk), 63% of the variability of the hourly equilibrium temperature was explained by hourly air temperature whereas 73% of the variability was explained for Little Southwest Miramichi River (LSWM)
The linear regression coefficient α was calculated at 0.43 ̊C for CatBk and a slightly higher value was obtained for LSWM (0.54 ̊C)
Summary
Water temperature has both economic and ecological significance when considering issues such as water quality and biotic conditions in rivers [1]. It is important to use adequate water temperature models to effectively predict water temperature variability. Water temperatures provide a better understanding of diel variability, including maximum and minimum water temperatures, which are very important for aquatic habitat and fisheries management [3]. Some studies have mainly focused on the impact of forest harvesting on water temperature while others have focused on fish habitat related issues. Studies have found that stream water temperature dynamics can influence many fish habitat conditions including the growth rate of fishes, aquatic invertebrates and others [6] [7]. Understanding the thermal regime of rivers in forested ecosystems has played an important role in the development of water temperature models, as valuable information has been learned from heat exchange processes [10]. Increased interest in river temperature has been noted recently due the potential effects of climate change [11] [12]
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