• hydrological variability;
  • indicators of hydrologic alteration;
  • Mann–Kendall non-parametric trend test;
  • Peace–Athabasca Delta


Natural and anthropogenically driven changes in upstream watershed conditions strongly influence the hydrological, geomorphological and ecological processes within downstream riverine and deltaic ecosystems. The goal of our study was to examine temporal trends and spatial patterns in ecologically relevant hydrological variables within the Athabasca River watershed and the downstream Peace–Athabasca Delta (PAD), located in northwestern Canada. Temporal trends for a suite of indicators of hydrologic alteration, appropriate for cold regions environments, were explored using non-parametric Mann–Kendall trend analysis. Results in the Lower Athabasca River (LAR) watershed were placed in a watershed-scale context. Across the two study periods (A – 1958–2009 and B – 1974–2009), results indicated decreasing trends in several key drivers of deltaic system hydrology, including short-term and long-term maximum and minimum runoff. In addition, an increasing trend in hydrograph variability was observed within the watershed. A spatially discrete pattern was apparent from the data, with a greater number of significant trends noted within the headwater region as compared with other areas of the watershed. Although earlier dates of annual freeze-up were observed across the watershed, there were few observable patterns in ice-on/ice-off conditions on the river. If these historical trends in freeze-up continue on the LAR, water levels in the PAD channels and inland wetlands could be affected, leading to reduced habitat diversity and altered ecosystem productivity. The study illustrates significant natural variability in the hydrological regime within the LAR that should be considered in future water management frameworks to ensure the preservation and maintenance of this Ramsar wetland site, particularly in the context of projected climate change and the increased water demands arising from upstream development associated with the Alberta Oil Sands. Copyright © 2012 John Wiley & Sons, Ltd.