Temporal trends in annual water yields from the Mackenzie, Saskatchewan-Nelson, Churchill, and Missouri-Mississippi River watersheds in western and northern Canada

Historical temporal trends in annual water yields were examined at 109 hydrometric monitoring stations in the Mackenzie, Saskatchewan-Nelson, Churchill, and Missouri-Mississippi River watersheds from the western Canadian provinces of Alberta, Saskatchewan, and northeastern British Columbia, as well as the Northwest Territories and the eastern portion of the Yukon territory. Effective drainage areas range in size from 325 to 1,680,000 (mean=65,600; median=9,300) km^2^, with associated hydrometric record lengths ranging between 18 and 97 (mean=41; median=38) years. Approximately three-quarters of the stations have no significant trend in average annual flow, with about equal numbers of stations exhibiting significant temporal increases or decreases in annual water yields. Southwestern Alberta and the southwestern Northwest Territories contain small clusters of stations with increasing water yield trends; clusters of decreasing water yield trends are primarily located in central and southern Alberta. The co-location of regions with clusters of both increasing and decreasing trends, or increasing/decreasing and no trends, complicates generalizing broader scale trends in annual water yields across these regions of Canada. No bias in the trend directions appears evident with either watershed size or the length of the hydrometric record