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REACH 8
From Bassano Dam to Oldman River

Sampling Site at Bow City Bridge Downstream of Ronalane Bridge Sampling Site

REACH DESCRIPTION
In Reach 8, the river flows from Bassano Dam cutting a fairly deep valley cross mostly undulating prairie lying within rural municipalities. The river ends where it joins the Oldman River and forms the South Saskatchewan River. This is the longest reach of the river at 185 kilometres. The South Saskatchewan River flows eastward through Medicine Hat into Saskatchewan, where it eventually drains via the Saskatchewan-Nelson River system into Hudson Bay.

This reach of the river is used less intensively than other reaches. Anglers enjoy the cool-water and cold-water fish species and the river is important for wildlife as well as livestock watering. Relatively less water is taken directly from the river for irrigation, industrial and domestic use.

As in Reaches 5, 6 and 7, the most significant pollution sources within this reach are upstream sources and local runoff from livestock operations and agricultural lands. A major influence on river water quality is also the withdrawal of water at the downstream boundary of Reach 7 for irrigation within the Eastern Irrigation District.

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WATER QUALITY INFORMATION
Some Issues: Sewage impact (improved as a result of treatment process), agricultural runoff, irrigation return flows and withdrawals, mercury levels in fish (consumption warning for walleye, pike).

Data is available from the following sources:

1) Alberta Environment

Long term sampling site, quarterly or monthly, plus pesticide at Bow City.
Long term sampling site, quarterly or monthly, plus pesticides at Ronalane Bridge.

Datasondes at Bow City, Bassano and Ronalane Bridge (at least July-August)
Phosphorus removal study – pesticide and algal biomass at Bow City and Ronalane Bridge, sediment at Ronalane

Synoptic Survey Sites (1995):

• Bow River below Bassano Dam
• Bow River at Bow City Bridge
• Minipoka Spillway
• Bow River at Scandia
• New West Coulee at HWY 36 crossing
• Bow River Drain "D" north of Vauxhall
• Sauki Spillway
• Bow Slope Canal Spillway
• Rolling Hills Canal #1 Spillway
• Twelve Mile Creek near Cecil
• Bow River at Ronalane Bridge (near the mouth)

Eastern Irrigation District (1997)
Daily sampling of fecal coliforms at Bassano Dam (April-October), except Sunday. Four reservoir sites sampled at least monthly for limited range of variables, and four return flow channels (two on Bow River), sampled (3x/year) for SAR, herbicides and pesticides. (co-ordinate grab sampling of Eastern Irrigation canal with Project 10 in Reach 7, and return flows with Project 6 above)

Siksika Nation (1997)
Sampling of the Bow River along reserve lands (5 sites), including one Bow River site downstream from the Bassano Dam, sampled monthly for a limited range of variables.

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ECOSYSTEM DESCRIPTION
In this reach, tree cover diminishes to scattered clumps of balsam poplar and plains cottonwood. Grasses and shrubs dominate the valley. Cattle grazing and beaver activity have not caused any changes in riparian vegetation since the 1880s.

As in Reaches 6 and 7, food resources for waterfowl in Reach 8 are plentiful as a result of nutrient enrichment from upstream sources and runoff from agriculture operations in the reach.

Wetland habitats along the reach are limited because of the steep banks of the Bow River valley. Also, withdrawals of significant amounts of water in the summer at Bassano Dam probably restrict downstream brood production. The water is too shallow to provide protection from predators and feeding habitat for diving ducks. Within the irrigation district, approximately 40 000 acres of wetland habitat is maintained by irrigation withdrawals.

Reach 8 provides highly important nesting and brood rearing habitat for geese. As in Reaches 6 and 7, cliffs along the river in Reach 8 provide additional nesting areas for Canada geese. Reach 8 is low importance staging habitat for geese and medium importance staging habitat for ducks.

Reach 8 does not support a substantial wildlife population as there is little cover available from trees, shrubs and rough terrain. Prairie grasslands are most common in Reach 8. Where there is cover, mule and white-tailed deer live year round, as do small numbers of pheasants and sharp-tailed grouse. One great blue heron rookery is located a few kilometres upstream of the Oldman River confluence.

Small groups and individual white pelicans and double-crested cormorants, probably from nearby Lake Newell, commonly live on the Bow River during the summer. Near the Oldman River confluence, the Bow River valley is key habitat for pronghorns (antelope).

Reach 8 is warm, highly productive biologically and frequently very shallow. A combination of low flows and warm-water temperatures in Reach 8, particularly in late summer, can decrease dissolved oxygen levels to the point where fish may be harmed (see Section IV for further information on aquatic plants and dissolved oxygen).

The low flows also force fish to concentrate in a few deep pools where they can be easily eaten by pelicans and cormorants. Although summer flows in Reach 8 are typically low, they may, at times, fluctuate drastically (short term range between 3 and 110 cubic metres per second) in response to irrigation requirements due to climatic conditions and TransAlta upstream storage needs. These irregular flows create unstable downstream habitat.

Sportfish identified in the reach include rainbow and brown trout, lake and mountain whitefish, northern pike, walleye, sauger, yellow perch, goldeye and lake sturgeon. Northern pike, walleye and lake whitefish are apparently the most abundant fish species in the reach. Trout and mountain whitefish are rare and decrease in number downstream. In the lower portion of the reach, increased flows from irrigation return water increase sportfish numbers.

Critical habitat areas have not been identified in this reach. Some rainbow trout and walleye spawning activity has been observed immediately below the Bassano Dam. Sauger spawning is suspected. Egg hatching is likely to have limited success because of lower summer flows, elevated summer water temperatures and river siltation. Irrigation return flows can cause erosion and carry sediments, which affect water quality and smother gravel areas with silt and sand.

However, lake whitefish, walleye and northern pike often use the areas around irrigation return discharges for rearing. Habitat for sportfish to spend and survive the winter is not likely affected in Reach 8 as flows are not diverted during the winter and natural flows are supplemented by releases by TransAlta Utilities.

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