Multiple-hydrologic stressors of a northern delta ecosystem

Abstract

During the early 1990's, two major ecosystems assessments weremade of the Peace-Athabasca-Delta (PAD), Canada, one of the world'slargest freshwater deltas. The Northern River Basins Study focussed onevaluating the effects of regulation on the Peace-Athabasca Delta,whereas the Peace-Athabasca Delta Technical Studies considered optionsfor restoring the role of water to the PAD. Both programs were initiatedbecause of concern over the health of this important northern aquaticsystem brought about by almost two decades of dry conditions.Recognizing the importance of water to restoring and maintainingbiological productivity and diversity of the PAD, a series of studieswere initiated to explain the reasons for the protracted drying and todesign methods to restore flooding. This manuscript examines the role offlow regulation as a hydrologic stressor affecting the Delta ecosystemand the results of studies that led to the definition of an additionalhydrologic stressor, climate variability. The suitability of adaptationstrategies, such as rock-filled weirs, artificial ice jams, and enhancedflow releases to deal with these multiple stressors are also reviewed.The results also reinforce a need for including river-ice processes intostudies and theories of large-river ecology.