Stream temperature is one of the important indicators of the health of stream ecosystem. Stream temperature can affect the physical and chemical properties of water, such as density, conductivity, pH and saturated dissolved oxygen concentration. Water temperature also influences the dynamics and distribution of aquatic species. For example, a fish species generally has a preferred water temperature range and a maximum water temperature that can be tolerated. Because water temperature affects the reaction rate of pollutants in the stream, the simulation of river water temperature is also the basis for watershed water quality modeling.

Stream temperature is mainly affected by the comprehensive influences of meteorological conditions and hydrological processes in the watershed, among which air temperature is an important factor as it affects the heat exchange between water surface and the atmosphere. Therefore, commonly used models for stream r temperature simulationused the linear or nonlinear regression between water temperature and air temperature, and this type of model ignores the influence of watershed runoff composition on water temperature. The proportion of surface runoff, lateral flow and groudwater runoff in the watershed also affects stream temperature, while snowmelt and glacier meltwater runoff also affect the water temperature through the cooling effect in the cold region watersheds.

Researcher Du Xinzhong, of the Innovation Team of Non-point Source Pollution Control of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS), developed an equilibrium temperature model (SWAT-ETM) based on the SWAT model for stream temperature simulation. The SWAT-ETM model considers the impact of runoff composition on water temperature, and uses the equilibrium temperature method  to simulate the heat exchange between water surface and the atmosphere . The model has been applied in different watersheds in China, the United States, and Canada (Duet al., 2018; Duet al., 2019; Duet al., 2020).

In order to further expand the applicability of the SWAT-ETM model, this study coupled the SWAT-ETM model with the glacier meltwater degree-day factor model (Figure 1) to simulate the impact of glacier meltwater runoff on stream temperature. The coupled model was applied in the Athabasca Basin in western Canada. The coupled model has a good simulation results for daily-scale stream temperature, reflecting the monthly and seasonal variations of stream temperatures (Figure 2).

The results of this research were published in the Journal of Hydrology under the title "Investigating the impacts of glacier melt on stream temperature in cold-region watershed: Coupling a glacier melt model with ahydrological model". Researcher Du Xinzhong from the IARRP is the first author and co-corresponding author of the paper. The co-authors of the paper are Professor Monireh Faramarzi and Gunjan Silwal from the Department of Atmospheric and Earth Sciences, University of Alberta, Canada. This research was supported by the National Natural Science Foundation of China (U20A20114; 42107076) and the Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences.

Paper link: https://www.sciencedirect.com/science/article/abs/pii/S0022169421013536 

References:

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Du, X., Shrestha, N.K., Wang, J., 2019. Assessing climate change impacts on stream

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