Physical processes governing the water budget of and the discharge from the Mackenzie Basin for the 1994/95 water year

The Mackenzie River of Canada is one of the largest rivers flowing into the Arctic Ocean. The Mackenzie basin water budget therefore plays an important role in the fresh water budget of the Arctic Ocean, and has a direct impact on the regional and/or global climate system.

The 1994/95 water year of the Mackenzie basin was characterized by record-low discharge and lake levels and by slightly-below normal precipitation. Also, the timing of discharge peak was about two weeks earlier than normal. To understand these features, a water budget study over the basin has been carried out using Canadian Meteorological Centre analyses, and particular low-discharge and spring-snow-melt events have been examined. This is the first effort to provide a comprehensive water budget over the Mackenzie Basin and it illustrates the year's below-normal atmospheric moisture convergence as well as other critical features.

A new governing equation for discharge was also derived by combining the atmospheric and the surface water budget equation and using the Gauss and the Green theorems. In the equation, two processes are very important from an atmospheric view. The first process is dependent on the nature of the circulation systems and the availability of water vapour, and the second is the alteration of moisture gradients through horizontal titling by the wind fields. Based on this equation, diagnoses using both the operational analysis as well as observational data were made, and the processes responsible for variations of the basin discharge on monthly and synoptic scales were examined.