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L'interaction entre les eaux souterraines (GW) et les eaux de surface (SW) des rivières peut affecter la quantité d'eau (disponibilité) et sa température, ce qui a un impact sur la vie aquatique. L'objectif de cette étude est de mieux comprendre et de quantifier l’interaction GW-SW à l’endroit de rivières nordiques affectées par les changements climatiques. Les travaux réalisés se sont attardés à identifier les zones d'écoulement de GW dans les rivières, analyser leurs caractéristiques hydrogéomorphologiques, quantifier le rôle de GW dans le bilan thermique des rivières et anticiper les changements dans l'interaction entre le GW et le SW en considérant les scénarios de changement climatique prévus. Deux rivières ont été sélectionnées pour l’étude afin d'évaluer les mécanismes physiques qui gouvernent l'interaction GW-SW selon deux climats différents et dans des conditions avec et sans pergélisol, soit pour la rivière Sainte-Marguerite localisée au sud de la province de Québec et sans pergélisol ainsi que la rivière Bérard au nord et avec un pergélisol discontinu. La méthodologie a consisté en une combinaison de techniques pour la collecte des données sur le terrain et des travaux de modélisation numérique pour simuler l’écoulement de l’eau et son comportement thermique. Les mesures sur le terrain ont consisté en l'imagerie thermique aérienne (TAI) des rivières, des mesures de radon dans l’eau pour l'identification des refuges thermiques et des zones de refroidissement, l'installation de piézomètres en berge et dans le lit des rivières ainsi que le suivi du niveau d'eau et la température avec des capteurs submersibles. De plus, des essais à l’infiltromètre et de traçage passif et actif de la chaleur dans le lit des cours d’eau ont permis de quantifier le taux d'infiltration de GW dans les rivières. Les données récoltées ont ensuite été utilisées pour le développement et l'étalonnage de modèles numériques couplés d’écoulement d’eau et de transfert de chaleur qui a per

Stream water temperature has a direct impact on the water quality and ecosystem through its influences on many chemical processes. The main objectives of this study is to investigate the long term monthly and yearly variation of stream water temperatures in cold regions for both historical and future periods. Firstly, the long-term trends (1961-2001) in the monthly and yearly time series of water temperature at Sapporo were identified. Then, to predict the future water temperatures, the approach of downscaling the outputs of a global climate model (GCM) to a local scale was investigated by employing the Statistical Downscaling Model to downscale air temperature (T) in both the present and future climate scenarios. The above downscaling approach was applied to the Sapporo meteorological station in Japan by simulating the local scale daily temperature based on large scale atmospheric variables including National Center for Environmental Prediction (NCEP) reanalysis datasets (1961-2000) and a general circulation model (HadCM3) outputs (1961-2099).

A model displaying river water temperatures was established, and applied to a small river basin. Based on the results, the effects of the alteration of the river basin on the budget and river water temperature were discussed. The model was a multi-layer mesh-typed runoff model, and the behavior of water and heat transference was depicted. Also, in order to verify the model, the daily changes of streamflow and river water temperature were measured and compared with the model results. From the calculation, the flow rate and river water temperature profile agreed well with the measured ones along the streamline. Using the model, the effects of deforestation and air temperature rise on river water temperature were discussed. With deforestation, the temperature in summer was calculated to rise and fall in winter. This was explained by the change of flow pass of surface and subsurface. The air temperature was thereafter changed in the model. From the simulation under the air temperature rises, the daily air temperature was evenly changed through a year, and the ratio of the change of the river water temperature to the air was less than unity (i. e., >1 °Criver water/°Cair). By close investigation of the model calculation, the most influential factor was determined to be subsurface temperature. The rise of surface temperature was also less than unity, due to the enhancement of heat loss with the augmentation of evaporation at the surface, and because the subsurface temperature is calculated on the surface temperature as boundary condition, rise of subsurface temperature was also less than unity. Overall, the mechanism of the alteration of river water temperature was described as follows: with the change of river basin land use or meteorological conditions, the pass of subsurface flow is changed, and the streamflow and river water temperature are also changed.

type:text, A model displaying river water temperatures was established, and applied to a small river basin. Based on the results, the effects of the alteration of the river basin on the budget and river water temperature were discussed. The model was a multi-layer mesh-typed runoff model, and the behavior of water and heat transference was depicted. Also, in order to verify the model, the daily changes of streamflow and river water temperature were measured and compared with the model results. From the calculation, the flow rate and river water temperature profile agreed well with the measured ones along the streamline. Using the model, the effects of deforestation and air temperature rise on river water temperature were discussed. With deforestation, the temperature in summer was calculated to rise and fall in winter. This was explained by the change of flow pass of surface and subsurface. The air temperature was thereafter changed in the model. From the simulation under the air temperature rises, the daily air temperature was evenly changed through a year, and the ratio of the change of the river water temperature to the air was less than unity (i. e., >1 °Criver water/°Cair). By close investigation of the model calculation, the most influential factor was determined to be subsurface temperature. The rise of surface temperature was also less than unity, due to the enhancement of heat loss with the augmentation of evaporation at the surface, and because the subsurface temperature is calculated on the surface temperature as boundary condition, rise of subsurface temperature was also less than unity. Overall, the mechanism of the alteration of river water temperature was described as follows: with the change of river basin land use or meteorological conditions, the pass of subsurface flow is changed, and the streamflow and river water temperature are also changed.

This report documents efforts to modify and implement the riverine water quality model, QUAL II, as a predictive/management tool for assessing effects of Lost Creek Dam operation on downstream temperatures in the Rogue River. Some of the topics addressed in this report are data synthesis of missing or unavailable observed data, results of calibration/verification, model sensitivity to operational changes, and software development to increase usability of the model. Each topic is discussed as related to the study objective; recommendations are presented to avoid model misuse.

A model displaying river water temperatures was established, and applied to a small river basin. Based on the results, the effects of the alteration of the river basin on the budget and river water temperature were discussed. The model was a multi-layer mesh-typed runoff model, and the behavior of water and heat transference was depicted. Also, in order to verify the model, the daily changes of streamflow and river water temperature were measured and compared with the model results. From the calculation, the flow rate and river water temperature profile agreed well with the measured ones along the streamline. Using the model, the effects of deforestation and air temperature rise on river water temperature were discussed. With deforestation, the temperature in summer was calculated to rise and fall in winter. This was explained by the change of flow pass of surface and subsurface. The air temperature was thereafter changed in the model. From the simulation under the air temperature rises, the daily air temperature was evenly changed through a year, and the ratio of the change of the river water temperature to the air was less than unity (i. e., >1 °Criver water/°Cair). By close investigation of the model calculation, the most influential factor was determined to be subsurface temperature. The rise of surface temperature was also less than unity, due to the enhancement of heat loss with the augmentation of evaporation at the surface, and because the subsurface temperature is calculated on the surface temperature as boundary condition, rise of subsurface temperature was also less than unity. Overall, the mechanism of the alteration of river water temperature was described as follows: with the change of river basin land use or meteorological conditions, the pass of subsurface flow is changed, and the streamflow and river water temperature are also changed.