Nature & Science

The North Saskatchewan Watershed in Alberta drains approximately 80,000 km2, or 12.5% of all land in Alberta, yet provides water for more than 25% of the population in our province. It begins at the Saskatchewan Glacier in Banff National Park, flowing 1,000 km east across Alberta and Saskatchewan before joining the South Saskatchewan River. From there, it flows into Lake Winnipeg in Manitoba and eventually empties into Hudson Bay.

In Alberta, the majority of the water in the North Saskatchewan River comes from the region of its headwaters, which is comprised of four subwatersheds: the Cline, Ram, Clearwater, and Brazeau. Collectively, these contribute approximately 88% of the total flow. The headwaters of mountain-fed prairie rivers are often referred to as “water towers” because they tend to provide the largest portion of total annual water within a watershed. This flow comes from precipitation that falls as rain or snow, which slowly filters into the river over time through numerous streams and tributaries and via groundwater infiltration. The North Saskatchewan River is the primary source of drinking water for Edmonton and dozens of other communities across the prairies, supplying water to more than 1.2 million people for human consumption, hydroelectric generation, oil and gas extraction, mining, and agricultural use. Much of the water use in the North Saskatchewan River is returned to the river after being used, either by going through a waste water treatment plant or a waste-water lagoon.

Although glacier melt contributes only a small portion of the overall flow (~1%), it provides much needed minimal flow during the hot and dry summer months. The flow is also affected by the two hydroelectric dams along the length of the river: the Brazeau Dam (1965) and the Bighorn Dam (1972). In order to ensure equitable and fair access to water, the North Saskatchewan River is also subject to the 1969 Master Agreement on Apportionment signed between Alberta, Saskatchewan, and Manitoba, which states that Alberta must not deplete more than 50 percent of its rivers flowing into Saskatchewan, as well as meet minimum flow requirements.

Whitemud Creek’s Oxbow Lake

By Kory deGroot

It’s difficult to speak about Edmonton without mentioning the North Saskatchewan River and its tributaries, which provide both drinking water and beautiful natural spaces for residents and wildlife alike. Surrounded North America’s largest interconnected park system, the river valley is a source of tremendous pride for the city.

When talking about rivers, oxbow lakes are a unique feature that is often overlooked. An oxbow lake is a free-standing waterbody that used to be a meander (i.e., a curve or a bend) in a river. As a river flows, it erodes the banks of the meander at its narrowest point. The river will eventually find the path of least resistance and break from the meander, leaving an oxbow lake behind. Because of the way they are formed, oxbow lakes are often in the shape of a “U.” Oxbow lakes are then fed by surface runoff or groundwater seepage, but they may become bogs or swamps or even dry out over time.

Oxbow lakes create an ecosystem unique to its flowing “parent” river. The still water is the perfect habitat for waterfowl, fish, or beavers to feed and breed. You will likely see bats and birds foraging for insects or roosting nearby. Oxbow lakes also provide greenhouse gas and nitrogen mitigation.

You can visit Edmonton’s only oxbow lake at Larch Sanctuary in Whitemud Creek Ravine. Another cool way to find oxbow lakes is by touring Google Maps and following almost any river’s path. You’ll likely see a few oxbow lakes along the way!

Tufa Springs at Whitemud Creek North

By Patsy Cotterill

The east slopes of Whitemud Creek near Fox Drive are the site of an interesting geological phenomenon known to geologists, naturalists, and historians as tufa springs. Here, water rich in calcium and iron flows year-round from steep embankments into the creek below. The slopes are covered with outcrops of a greyish rock called tufa, formed over long periods of time by precipitation of calcium carbonate and other minerals from the spring water at ambient temperatures. The soil is also rich in calcium carbonate in a form called marl.

The springs create conditions similar to those of peatlands in the boreal forest, such that wet pockets in the white spruce forest are home to orchids, including lady’s slippers (Cypripedium species), round-leaved and northern green orchids, and a number of sedges, grasses, and mosses.

Unfortunately, the lower slopes in particular see heavy recreational use and have become degraded by a complex network of man-made trails with loss of plant ground cover. The City of Edmonton needs to provide protected status for this area, and to rehabilitate the main trail, which is heavily eroded by the water flows. Signage to educate the public on its sensitivity and interesting geology would help create respect for this beautiful and unique area of the river valley.

Water Levels and Flows in the NSR

By Patsy Cotterill

People have been commenting on the low water levels in the creeks and the North Saskatchewan River this September. Certainly, there is a striking contrast between those levels in April and May this year, when Whitemud Creek was a raging torrent scouring its banks, and how they are in August and September.

High water levels continued throughout July as a result of abundant rainfall, allowing a larger-than-usual number of people to try their hands at fishing, but declined throughout August and September.

Creeks drain into rivers, and the rivers drain into the ocean, so without replenishment by snow and meltwater in the spring and early summer and precipitation thereafter, their levels must eventually drop. However, water levels in the North Saskatchewan River are also influenced by the operation of the Bighorn and Brazeau hydroelectric dams upstream, which retain water in their reservoirs or release it as required for hydroelectricity generation and stream regulation. This in turn helps to maintain reliable water supplies year-round and prevent flooding.

The occasional white spruce or mature balsam poplar is uprooted by erosion of the banks and falls down or across the stream. But, interestingly, little standing dead vegetation remains along the creeks and riverbanks despite spring and summer floods. There are probably two reasons for this. One is that the water draws down fairly rapidly in the creeks between rainfall events. Another is that the trees, shrubs, and riparian herbaceous plants that vegetate the low-lying floodplains (as opposed to the terraces and slopes) are tolerant of short periods of flooding. They include balsam poplars, river alders, and Manitoba maples, along with shrubs such as sandbar willow, hungry willow, and red-osier dogwood. These plants can quickly grow new, shallow roots to replace those that have died from drowning. In addition, sandbar willow has horizontal underground stems (rhizomes) that can send up shoots quickly to recolonize areas laid bare by water.

By contrast, in level or low-lying areas, such as the wetlands at Clifford E. Lee Nature Sanctuary, water cannot easily drain away, and once the soil has become waterlogged it accumulates above ground. Standing water more than a foot high that has remained all season has killed a lot of trees, mainly aspen, birch, and willows growing along the lake and boardwalk. The height of these dying trees is a measure of the time that has elapsed since the last flooding occurred. As a result, the forested area will be reduced to higher ground and the area covered by lake and marsh at the sanctuary will increase.