A review of hydroecological results of the Northern River Basins Study, Canada. Part 1. Peace and Slave rivers

Abstract

AbstractDuring the early 1990s a multi‐component research programme was initiated by the Northern River Basins Study (NRBS) in Canada to answer the question: How does and how could flow regulation affect the aquatic ecosystem? Research focused on the major headwaters of the Mackenzie River, the Peace and Slave rivers, which became regulated in 1968 by the W.A.C. Bennett Dam in the Rocky Mountains. The lack of knowledge about the hydroecology of large northern rivers as well as a paucity of data for this relatively isolated basin required that studies be undertaken to assess how flow regulation had modified the physical template of this system. Research focused on quantifying the regulation effects on the flow regime, ice conditions, fluvial geomorphology and riparian vegetation of the Peace and Slave rivers and the Slave River Delta.Results of the NRBS studies indicate that regulation of the Peace River has shifted the pattern of seasonal flows and damped flow extremes creating a less variable annual regime. Increased winter releases from the reservoir have virtually eliminated the formation of a complete winter ice cover for a significant distance below the dam and delayed ice‐cover formation farther downstream. Higher ice levels that accompany increased winter flows are thought to affect the frequency and magnitude of ecologically important ice‐induced floods that occur during the spring. Although more difficult to link solely to the effects of flow regulation, pronounced morphologic and vegetation changes have been observed along the Peace River, including channel narrowing via the abandonment of secondary/backwater channels and in‐channel shoaling along the lower reaches. Vegetation succession has been especially evident on abandoned bar surfaces. Morphological changes were also observed in the Slave River Delta, particularly along the ecologically sensitive outer margin of the delta. Copyright © 2002 Environment Canada. Published by John Wiley & Sons, Ltd.