By Mathieu Lebel, Advisor, Water Management & Rob Powell, Senior Officer, Priority Conservation Programs
This is part of a special WWF blog series exploring the Athabasca River’s unique ecosystem and water management, and most importantly, how we can ensure its healthy future. This is the second blog of the series – the first is posted here. The Athabasca is also featured in WWF’s Freshwater Health Assessments.
Determining how much water a river needs is a challenge people are wrestling with around the world, but some key principles have emerged from the scientific community. Among them is the need for protection during critical low flow periods, a primary concern for Alberta’s lower Athabasca River.
Looking across the country it is easy to see that Canada is home to a great diversity of rivers. In Alberta we have exceptionally large ones like the Slave River that flows into the Northwest Territories, and much smaller ones like the Milk River that flows from and back into Montana. Rivers across the country also have different patterns of water flows and levels, and are home to different species. For example, British Columbia’s Fraser River sustains white sturgeon and 5 species of Pacific salmon (chinook, chum, coho, pink, and sockeye) while brook trout are found in many rivers and streams across Ontario. All rivers provide a range of social, economic, and environmental benefits, and all require an acceptable quantity and quality of water at the right times to remain healthy. Protecting these water needs, commonly referred to as environmental flows, is now a global water management imperative.
Clearly, with the great diversity of rivers across the nation, the environmental flows of one river may not be the same as those of another. So the question that comes to mind is: ‘what are the key principles of protecting and restoring a river’s environmental flows?’ This question is particularly relevant for rivers like the lower Athabasca where public consultation and the completion of an updated water management plan have long been expected. Fortunately, we can look to both specific scientific studies that have been conducted on the Athabasca as well as international and national best practices to see what a leading approach to environmental flow protection and water management would look like for the lower Athabasca River.
Among the key principles of environmental flow protection emerging across the globe, Canada, and in Alberta, is a two-part approach that involves (1) a cumulative alteration limit from natural flow and (2) suspending water withdrawals during critical low flow periods. This second part is termed an ecosystem base flow or cut-off limit and is essentially a flow at or below which the aquatic ecosystem requires all available water. The concept of an ecosystem base flow is fairly intuitive: low flows may be stressful for fish and other aquatic life as habitat is reduced and water quality may change, and so continuing to take water out of rivers at these times poses a heightened risk to the aquatic ecosystem. In Canada, low flows may occur in both summer and winter – in the lower Athabasca they occur during the winter when the river is covered in ice, which can be a stressful period on its own for aquatic life.
Internationally, an ecosystem base flow is applied and recommended as part of environmental flows protection and water management in many jurisdictions including Florida and the United Kingdom. At a national level the Department of Fisheries and Oceans Canada has recommended that a cut-off limit should be part of the overall approach to conserve and protect fisheries, while at a provincial level an ecosystem base flow is part of the Alberta Desk-top method for establishing environmental flows. Specific to the lower Athabasca, it has been recommended from a science perspective that ‘a flow should be established for the Lower Athabasca River below which there would be no water withdrawal.’ It should be noted that determining the exact river flow for an ecosystem base flow remains a scientific challenge, so it is often recommended that they be set using a precautionary approach and may be adjusted over time as additional information becomes available.
Protection during critical low flow periods is central to securing a river’s environmental flows and sustainable water management. For the lower Athabasca River, this can be accomplished in a new water management plan.