Figure Eight Lake

Basic Info
Map Sheets84C/5
Lat / Long56.3000000, -117.9000000
56°17'N, 117°54'W
Area0.368 km2
Max depth6 m
Mean depth3.0 m
Dr. Basin Area4.47 km2
Dam, WeirDam
Drainage BasinPeace River Basin
Camp GroundPresent
Boat LaunchPresent
Sport FishRainbow Trout
Trophic StatusHyper-Eutrophic
TP x182 µg/L
CHLORO x99.1 µg/L
TDS xNo Data mg/L
Photo credit: E.E. Prepas


Figure Eight Lake is a tiny, naturally productive lake in northwestern Alberta. It is located in a treed setting, 45 km northwest of the town of Peace River and 7 km northwest of Lac Cardinal. For over three decades, Figure Eight Lake has received considerable attention from local groups and the provincial government because it is one of the few lakes in the Peace River region that serves as both a sport fishery for trout and a recreational area. To reach Figure Eight Lake, take Highway 2 west from Peace River for 20 km to the junction with Highway 35. Follow the latter north for 9 km and then turn west onto Secondary Road 737 and continue for 16 km. The lake is just northwest of the secondary road (FIGURE 1); the turnoff is well marked with a large, carved wooden sign. Alternatively, the lake can be reached by continuing on Highway 2, past Highway 35, to the hamlet of Brownvale. At Brownvale, turn north on Secondary Road 737 and continue to the turnoff for Figure Eight Lake.

Figure Eight Lake is situated between the forested area of the Whitemud Hills to the north and the agricultural lands of the lower Peace River basin to the south and east (Makowecki and Bishop 1978). Although a few settlers had arrived to farm the region before the turn of the century, homesteading began in earnest about 1908 (MacGregor 1972). The number of farms in the area increased rapidly until 1931 (Scheelar and Odynsky 1968).

Figure Eight Lake is a regulated lake that drains south, then southeast to Lac Cardinal. The Peace River area has a shortage of recreational lakes. Consequently, an earthen weir was built on the outflow to raise the lake level for recreational purposes. In 1970, the old weir was replaced with a fixed-crest earthfill dam (Alta. For. Ld. Wild. n.d.). These projects were supported by a number of local and provincial groups, including the Brownvale Community Club, Figure Eight Lake Recreation Club, Alberta Environment, Ducks Unlimited (Canada) and Fish and Wildlife Division, including Buck for Wildlife. In 1975, the first boat launch and pier were constructed at the southwest corner of the lake and fences were erected to protect the shoreline from cattle grazing. In 1981, a site development program was drawn up for the lake (Butler Krebes Assoc. Ltd. 1981). From 1986 through 1988, Alberta Environment and the Lac Cardinal and Figure Eight Lake Recreational Associations coordinated a project to install 42 overnight campsites, a large playground, a concrete boat launch with a dock, a day-use area, a sand beach and two ball diamonds on the southwest corner of the lake (Becker 1988). The group also has plans for ski and nature trails around the lake. The control structure and recreational facilities at the lake are now operated and maintained by Alberta Environment. There are no other developments on the lakeshore.

Figure Eight Lake takes its name from the shape it had before 1970 when the water level was low; in these earlier days the lake had two basins and resembled a figure eight.

Figure Eight Lake has algal blooms in summer, to the extent that it has a tendency to winterkill and occasionally summerkill. Since 1980, Fish and Wildlife Division, Alberta Environment, and recently the University of Alberta, have supported a program to reduce excessive algal blooms and the risk of fish die-offs in the lake. This program has entailed the use of copper sulphate (or "bluestone") from 1980 through 1984, lime (both calcium carbonate and calcium hydroxide) in 1986 and 1987, and the installation of an aerator in 1986. These programs have enhanced the sport fishery (Alta. For. Ld. Wild. n.d.).

The lake is stocked annually with rainbow trout. It is a popular location for family and group recreational fishing and camping, particularly on warm summer weekends. Fishing for bait fish and use of bait fish are not permitted in Figure Eight Lake (Alta. For. Ld. Wild. 1989); only electric motors are permitted on the lake (Alta. For. Ld. Wild. 1988).

Drainage Basin Characteristics

The drainage basin of Figure Eight Lake is gently undulating, with slopes of 0.5 to 2%. Most of the drainage basin is covered by trembling aspen/balsam poplar forest, with 0.37 km2, or 8% of the drainage area, cleared for agriculture (FIGURE 1). The cleared areas are leased for cattle grazing. The soils are mainly Solonetzic Gray Luvisols (TABLE 1) and the agricultural capability of the land is rated as fair to fairly good (Scheelar and Odynsky 1968). All of the land in the watershed belongs to the Crown.

One stream flows into the north end of the lake. This stream is dotted with beaver dams and flows through a low area directly north of the western edge of the lake. The stream flows only during spring runoff (Guenther 1983). During a study conducted between 8 April and 27 August 1986, most of the flow (64%) occurred within the first four days of runoff. No measurable flow was recorded past 7 May 1986 (Prepas and Murphy 1987). Outflow is channeled through the control structure at the south end of the lake. Flow is intermittent in the outflow channel, which flows into Lac Cardinal.

Lake Basin Characteristics

Figure Eight Lake is a tiny lake (TABLE 2, FIGURE 2) with three basins: a shallow southern basin, a shallower and smaller central basin, and a very shallow and small northern basin (maximum depths 6, 5 and 3 m, respectively).

In 1955, the maximum depth of Figure Eight Lake was approximately 3 m. In 1956, local residents constructed a small earthfill dam on the lake's outflow to raise the water level by almost 1 m, to a maximum depth of over 4 m. This dam was washed out and rebuilt at least once before 1968, when the lake was chosen by the Brownvale Community Club and its subsidiary, the Figure Eight Lake Recreation Club, as the site for a lake improvement project (Makowecki and Bishop 1978; Acres Int. Ltd. 1985). In 1970, the club cleared away the old dam and the brush from the flooded and nearshore areas, and rebuilt the dam to a maximum lake depth of 4.6 m. To increase the size of the lake and overcome problems with erosion of the earthfill dam, the dam was upgraded in 1973 by Alberta Environment. The works consist of a drop inlet spillway to accommodate a maximum lake depth of 6 m, an emergency spillway, riprap protection and downstream channel improvement. The increased depth significantly increased both the area and capacity of the lake (FIGURE 3) and the new maximum depth was considered adequate to ensure the overwintering of sport fish (Alta. For. Ld. Wild. n.d.).

The elevation of Figure Eight Lake has been monitored since 1982 (FIGURE 4). Over the period of record, the water levels have fluctuated by a maximum of 0.32 m. The maximum water level, 683.17 m, was recorded on 21 May 1986, and the minimum level, 682.85 m, was recorded on 5 October 1982.

Water Quality

The water quality of the two larger basins of Figure Eight Lake have been studied since 1971 by Fish and Wildlife Division (Alta. For. Ld. Wild. n.d.; Bishop 1979), in 1980 and 1984 by Alberta Environment (summarized in Acres Int. Ltd. 1985), and from 1985 through 1989 by the University of Alberta and Environment Canada (Prepas et al. n.d.; 1987; 1988; 1990; Prepas and Murphy 1987; Manning et al. 1988). Sediment phosphorus chemistry was examined in August 1986 (Shaw and Prepas 1989).

The water is well-buffered (average total alkalinity 110 mg/L CaCO3) and slightly coloured. The dominant ions are bicarbonate and calcium (TABLE 3).

The two deeper basins are weakly thermally stratified during most of the summer, are mixed fairly well during fall and are thermally stratified again under ice cover (illustrated in Figure 5 with data from the deepest basin). The lake is ice-covered for a full six months. When the lake water is thermally stratified, water over the bottom sediments becomes anoxic (FIGURE 6). Under ice cover, oxygen depletion is extremely rapid and the lake is often anoxic by January. For the first seven weeks of ice cover in 1985, dissolved oxygen consumption rates were 0.610 g/m2 per day.

Figure Eight Lake is hyper-eutrophic. Total phosphorus and chlorophyll a concentrations can exceed 200 µg/L in the surface waters (TABLE 4, FIGURE 7). Total phosphorus increases in the surface waters during summer and again under ice in winter. Phosphorus concentrations over the sediments can surpass 700 µg/L. Phosphorus concentrations in the shallow porewater (over 3,600 µg/L soluble reactive phosphorus) and potentially mobile phosphorus in the bottom sediments were the highest measured in nine Alberta lakes. Thus, there is rapid recycling of phosphorus between the open water and the sediments of Figure Eight Lake. Total iron concentrations are relatively high and reflect iron deposits in the region. The possible relationship between iron and phosphorus remains undetermined for this lake; iron can immobilize phosphorus and reduce phosphorus concentrations in the surface waters of some lakes.

The inflowing stream is a major phosphorus source during spring runoff. In April 1986, both total phosphorus and total iron concentrations were high in the stream; total phosphorus averaged 671 µg/L and total iron averaged 411 µg/L. During peak flow in late April, total iron concentrations reached a high of 1,560 µg/L.

After the modified reservoir was filled in the early 1970s, the sport fishery blossomed initially, then declined as a result of excessive algal growth, which caused low dissolved oxygen concentrations (Makowecki and Bishop 1978). This algal problem spurred exploration of alternatives to improve the water quality of Figure Eight Lake, which included chemical treatment, aeration, and diversion of water into the lake from the major tributary to Lac Cardinal, which flows to the west of Figure Eight Lake (Guenther 1983). Chemical treatment (TABLE 5) and winter aeration have been implemented. Water diversion has not been implemented because increased flow would not enhance water quality. Another alternative, increasing lake depth, is not feasible because of the large flat low-lying area at the north end of the lake, thus a very large area would be flooded with a 2-m increase in water levels (Prepas et al. 1987).

Figure Eight Lake has been treated with chemicals to reduce algal biomass in five of the last eight years (TABLE 5). The data in TABLE 3, TABLE 4, Figure 6, and Figure 7, and the previous discussion on water quality, were selected to represent the natural state of the lake. Following the copper sulphate treatments, algal biomass was reduced, and after some but not all treatments, under-ice dissolved oxygen concentrations improved. However, concern was raised about the accumulation of copper in the sediments of the lake and long-term toxicity problems associated with this treatment. Some of these concerns were confirmed in a 1985 study in which it was documented that copper accumulated in the sediments had suppressed normal bacterial activity for up to one year after treatment and had recycled into the open water for brief periods. In addition, amphipods (a prey popular with trout) disappeared from Figure Eight Lake from June 1980, when the lake was first treated with copper sulphate, until May 1986, after treatment had been discontinued for almost two years, when they returned in high numbers.

In 1986 and 1987, the lake was treated with two forms of lime (TABLE 5). These treatments had the effect of reducing algal biomass for 1987 and most of 1988. In 1987, both total phosphorus and chlorophyll a concentrations were reduced to less than half of pretreatment levels (246 ± 14 to 75 ± 8 µg/L total phosphorus and 96 ± 14 to 12 ± 7 µg/L chlorophyll a). In addition, under-ice dissolved oxygen depletion rates dropped from a pretreatment rate of 0.610 to 0.363 g O2/m2 per day.

An aerator was installed in Figure Eight Lake in October 1986. In the first winter, two events combined to eliminate any significant improvement in under-ice oxygen conditions. First, it was an unusual fall: it was warm until late October, then it quickly turned cold. Consequently, the lake became ice covered when the water was less than 45% saturated with dissolved oxygen (less than 5.4 mg/L). Dissolved oxygen concentrations at the same time in 1985 were 2.3 times higher (12.4 mg/L). In addition, dissolved oxygen consumption rates were still high in the winter of 1986/87 (0.610 g/m2 per day). The aerator could not inject enough air to keep dissolved oxygen levels up that winter. In contrast, in 1987/88, dissolved oxygen concentrations were high (10.9 mg/L) at the onset of ice cover and consumption rates were much lower due to the reduced algal production during the previous summer. Consequently, the aerator was able to ensure that trout could overwinter. The trout overwintered because of the combination of low dissolved oxygen consumption rates following effects of lime treatments, and the extra oxygen injected with the aerator (Walty 1988; Prepas et al. 1990).

Biological Characteristics


Algal biomass and species composition have been monitored in Figure Eight Lake since the mid-1970s (Alta. For. Ld. Wild. n.d.; Prepas et al. 1987; 1988; Prepas and Murphy 1987). The dominant alga in most summers is the blue-green, Aphanizomenon flos-aquae.

Aquatic macrophytes in the southwest part of the lake have been monitored annually since 1985 by the University of Alberta (FIGURE 8). Plants were most concentrated in areas with shallow slopes and depths of less than 1 m but rooted plants were found to a depth of 2 m. Macrophyte biomass declined slightly after the lime treatments in 1986 and 1987, even though light penetration improved substantially. This unexpected change could be related to decreased phosphorus availablility in the bottom sediments. The following data on fresh weight (g/m2) are averages for all samples collected in July at one depth (±1 S.E.).


1 m
240 (70)
170 (104)
193 (136)
2 m
199 (77)
250 (82)
56 (20)


There are no quantitative data on the invertebrates in Figure Eight Lake.


Two species of fish inhabit Figure Eight Lake: rainbow trout, which are stocked annually, and fathead minnows. Ninespine sticklebacks have been observed below the dam. Rainbow trout production, actual and potential, has been evaluated by Fish and Wildlife Division since 1971 (Alta. For. Ld. Wild. n.d.; Schroeder 1975; Makowecki and Bishop 1978; Bishop 1979; Schwanke and Schroeder 1983; Walty 1988).

The lake was first stocked by Fish and Wildlife Division in 1956 with 750 adult northern pike. They did not become established. Since 1971, the lake has been stocked annually with fingerling rainbow trout (7 to 10 cm), which rapidly grow to catchable size. Larger trout (up to 18 cm in length) are also stocked, to provide some immediate angling opportunities. From 1971 through 1979, an average of 5,600 (range 3,000 to 15,000) rainbow trout were planted yearly. In 1980, stocking increased about 6-fold and an average of 32,300 rainbow trout (range 26,900 to 48,000) were added from 1980 through 1988. In years when Fish and Wildlife Division predicted that the lake would winterkill, salvage netting permits were issued so the trout could be harvested before dissolved oxygen reached critically low concentrations and the fish died.

In June 1983, a three-day creel survey was conducted by Fish and Wildlife Division. The catch per unit effort was 0.56 rainbow trout/ hour. Growth rates of rainbow trout in Figure Eight Lake are the highest in the region. From 1980 through 1983, fingerlings grew an average of 1.66 g/day and 1.16 mm/day during the open-water period.


Ducks Unlimited (Canada) (1982) report that there is some good upland nesting cover for waterfowl at Figure Eight Lake. However, the generally steep shoreline and poor distribution of emergent and submergent plants restricts the potential for waterfowl production. Nesting species include mainly Lesser Scaup, American Widgeons, teal, Ruddy Ducks, and White-winger Scoters, with production estimated at 4.8 broods per km of shoreline.

E.E. Prepas


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-----. n.d.[b]. Tech. Serv. Div., Surv. Br. Unpubl. data, Edmonton.

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