An Overview of Temporary Stream Hydrology in Canada

Temporary streams lack streamflow at some time in the seasonal cycle, and include ephemeral, intermittent and episodic streams. They often serve as headwaters for the perennial stream network in a drainage basin, and given that headwater streams can comprise the majority of the drainage network, temporary streams are significant hydrologic features across the country. Nevertheless, they have received relatively little attention compared to perennial streams. In addition, much previous work on temporary streams has focussed on semi-arid and arid landscapes where annual evapotranspiration exceeds annual precipitation. While such climatic conditions do control the occurrence of temporary streams in some regions in Canada, temporary streams can also occur in sub-humid and humid climates. This paper examines the major controls on the occurrence and behaviour of temporary streams at the regional and reach scales in Canada; however, where necessary we also review literature from outside Canada on aspects of temporary streams relevant to the Canadian context. The paper assesses the temporal dynamics of temporary streams, along with key aspects of their geomorphology and ecology as well as current monitoring and modelling approaches. Temporary streams are very sensitive to anthropogenic and natural activities that can modify their hydrology and hydroecology, and they deserve greater attention from the Canadian hydrological community. Improved monitoring and process studies should be pursued in Canada.