Reesor Lake

The contents of this online version has not been altered or modified from the original 1990 publication. It is reasonable to assume that much of the data e.g. water levels, camp grounds/boat launches, etc. is out of date. For updated or additional information on any of the lakes in this atlas please go to Environment Alberta's water web site.

Basic Info
Map Sheets72E/9
Lat / Long49.6666667, -110.1166667
49°40'N, 110°7'W
Area0.51 km2
Max depth5.5 m
Mean depth3.7 m
Dr. Basin Area5.58 km2
Dam, WeirDam
Drainage BasinMilk River Basin
Camp GroundPresent
Boat LaunchPresent
Sport FishRainbow Trout
Trophic StatusEutrophic
TP x36 µg/L
CHLORO x14.0 µg/L
TDS x130 mg/L
Photo credit: Alberta Recreation and Parks


Reesor Lake is a small, popular trout-fishing reservoir located within Cypress Hills Provincial Park in the Municipal District of Cypress. It was named after David William Reesor, the son of a Canadian senator, who settled in the area in 1900. The original Reesor ranch house still stands near the shore (Alta. Cult. Multicult. n.d.). Prior to 1960, the lake was two small, separate water bodies, called Twin Lakes. In 1960, a dam was constructed across the southeast end of the valley where the two lakes were located. Water was diverted into the reservoir from Battle Creek, raising the water level and thus creating a single lake (FIGURE 1).

Cypress Hills Provincial Park is situated approximately 65 km southeast of Medicine Hat, off Highway 41. Of the 12 campgrounds in the park, two are located near Reesor Lake (FIGURE 2). The first of these is Reesor Lake Dock Campground, which is situated on the north shore of the lake off the Reesor Lake Road. It is open year-round and has 24 random campsites, a water pump, a fishing pier and a boat launch. The second campground, Reesor Lake Campground, is located south of the lake on the south side of Battle Creek. It is open from May to September and provides 40 campsites, including 7 walk-in tenting sites, tap water, picnic tables, a picnic shelter, a playground and weekly interpretive programs. A boat launch is located at the western end of the dam. The only boat motors allowed on the lake are electric (Alta. For. Ld. Wild. 1988).

Reesor Lake has one of the more important sport fisheries in southern Alberta and many people visit Cypress Hills Provincial Park only to fish the lake for rainbow trout (Bishop 1989). Fishing regulations prohibit the use of bait fish in the lake (Alta. For. Ld. Wild. 1989). The water is clear during most of the year, but turns green in midsummer. Extensive areas of aquatic macrophytes cover much of the lake bottom and interfere with angling during late summer.

Drainage Basin Characteristics

The Cypress Hills are a remnant of a large depositional plateau that existed about 40 million years ago, but which has eroded since that time. During the Wisconsin Age, the ice sheet that advanced into the region from the north flowed around the plateau and engulfed all but the top 90 m. The plateau is now about 130-km long and 25- to 40-km wide. One-third of it lies in Alberta and the remainder is located in Saskatchewan. The Cypress Hills are the highest point of land in Canada between Labrador and the Rocky Mountains. They form part of the divide that separates streams that flow to Hudson's Bay via the South Saskatchewan River system from streams that flow to the Gulf of Mexico via the Mississippi River system.

Although the natural drainage basin surrounding Reesor Lake is quite small, it is 11 times larger than the lake (Tables 1, 2; FIGURE 1). There are no defined natural inlets, and most of the water that enters the lake is brought by a channel and concrete pipe from Battle Creek (FIGURE 2).

The bedrock in the drainage basin consists of the Frenchman Formation at lower elevations near the lake and the Ravenscrag Formation along the upper slopes of the plateau (TABLE 1). Surficial deposits on heavily wooded slopes consist mainly of colluvium, which is composed of sand, silt, clay and bedrock debris that has moved down slope, whereas surficial deposits at the southern end of the lake and along Battle Creek consist mainly of alluvium, which consists of sediments laid down along river beds and floodplains. The alluvial deposits range from gravel and sand to silt and clay (Lombard North Group 1973).

Reesor Lake is situated in a deep, wooded valley. All of the land in the watershed is part of Cypress Hills Provincial Park. The north-facing slopes to the southwest of the lake are forested with white spruce, lodgepole pine and trembling aspen. The latter two species are also the main trees near the lake. The land is more open on the northeast side of the lake, where the vegetation is shrubland, trembling aspen groveland, and fescue and mixed grasslands (Lombard North Group 1973).

Lake Basin Characteristics

Reesor Lake is a long, narrow, shallow water body that is oriented in a northwest-southeast direction (FIGURE 2). It is a maximum of 2.1-km long and 0.5-km wide, and covers an area of only 0.51 km2 at full supply level. The northwestern half of the lake has a flat bottom that reaches a maximum depth between 2 and 5 m. The southeastern half is somewhat deeper: the sides of the basin slope gently to a maximum depth at full supply level of about 5.5 m.

The control structures that created Reesor Lake were built in 1958 by the Prairie Farm Rehabilitation Administration of the federal Department of Agriculture (Agric. Can. 1962). They were upgraded in 1976 by Alberta Environment, which accepted control and maintenance responsibilities in the early 1970s. The 1976 concrete weir and diversion structure in Battle Creek directs water into a short channel that flows into a concrete pipe that enters the lake on the western side of the dam. The amount of water flowing through the pipe is controlled by two gates. The dam is an earthfill structure that has a riparian outlet pipe and gate at its eastern end and two drop-inlet spillways. Outflow is directed into a natural channel which drains back to Battle Creek. Water flows out through the smaller of the two spillways when the lake's elevation reaches the full supply level of 1,226.52 m (TABLE 2, FIGURE 3). The larger spillway is used for emergencies, when the water level rises above 1,226.67 m. Regular releases of water through the outlet gate maintain flow in the stream channel and special releases meet the needs of downstream water users (Didyk 1988).

The elevation of Reesor Lake has been monitored since 1965 (FIGURE 4). The historic minimum (1,225.48 m) was recorded in 1980, after the lake level was lowered in late 1979 to facilitate chemical treatment for removal of white suckers. The historic maximum (1,226.57 m) was recorded in May 1986. During the 1960s and 1970s, the lake's elevation was kept near 1,225.91 m, rather than at the design full supply level of 1,226.52 m. Water depths at the lower level were marginal for fish survival (Underwood, McLellan & Assoc. Ltd. 1976) and fish kills occurred in the winters of 1978/79 and 1981/82. However, since 1982, the elevation has been maintained closer to the full supply level, and no fish kills have been reported since the winter of 1981/82.

Water Quality

Water quality in Reesor Lake has been monitored since 1982 by Alberta Environment and Alberta Recreation and Parks (Alta. Envir. n.d.[a]). As well, winter dissolved oxygen concentrations have been monitored annually by Fish and Wildlife Division since 1972 (Alta. For. Ld. Wild. n.d.; English 1979).

Reesor Lake has fresh water that is well-buffered and less hard than the water in many Alberta lakes (TABLE 3). The dominant ions are calcium and bicarbonate. Turbidity is low and the water is quite transparent (TABLE 4).

The lake is typical of shallow lakes in Alberta: it is easily mixed by wind and, therefore, it rarely stratifies during summer. Levels of dissolved oxygen were uniformly high from top to bottom in August of 1984 (FIGURE 5) and 1987, and in September of 1985 and 1986. During winter, dissolved oxygen can become depleted near the bottom, as in March 1985 (FIGURE 5). Winterkill is not a major problem, however, because the surface water usually contains sufficient dissolved oxygen for fish survival. Exceptions occurred in the winters of 1978/79 and 1981/82, when dissolved oxygen declined to critical levels.

Reesor Lake is eutrophic. The highest chlorophyll a concentration ever recorded in the lake (64 5g/L) occurred in September 1984 (FIGURE 6). The long-term average recorded during the open-water season from 1983 to 1987, however, is much lower (14.0 5g/L, TABLE 4). Chlorophyll a concentrations often reach a small peak in May but the highest levels occur in August or September. Total phosphorus is highest in late summer in most years, as well, probably because phosphorus is released from the bottom sediments and then mixed into the overlying water.

Biological Characteristics


There are no data available for the phytoplankton community in Reesor Lake.

Brief observations of aquatic macrophytes were made by Fish and Wildlife Division on 1 June 1978 (English 1979). Plants grew densely around the entire shoreline to a depth of approximately 4 m, and covered 70 to 80% of the lake bottom. The emergent species identified were common cattail (Typha latifolia) and bulrush (Scirpus sp.), and the submergent species were Richardson pondweed (Potamogeton richardsonii) and coontail (Ceratophyllum demersum).


The invertebrates in Reesor Lake were sampled by Fish and Wildlife Division on 1 June 1978 (English 1979). Almost 79% of the total number of zooplankton in the sample (138/L) was copepods, 20% was rotifers and less than 2% was cladocerans. The standing crop of zooplankton, particularly Cladocera, was considered to be relatively low. Four samples of benthos were taken with an Ekman dredge from a depth of 6 m. The samples included midges (Chironomidae) and aquatic earthworms (Oligochaeta). Chironomids dominated by weight (6 g/m2 wet weight), but oligochaetes were more numerous. Many clam shells (Pelecypoda) were included in the sample, but none contained live animals. The standing crop of benthos (7 g/m2 wet weight) was considered to be very low.


Reesor Lake is managed as a rainbow trout fishery. This species was stocked first in 1960. With the exception of 1979, the lake has been stocked annually since 1967. Between 1981 and 1988, approximately 63,000 trout (1 235 trout/ha) were planted each year (Alta. En. Nat. Resour. 1981-1985; Alta. For. Ld. Wild. 1986-1988). Regular stocking is necessary to maintain the rainbow trout population, since there is no trout spawning habitat available. Brown trout were stocked from 1954 to 1956, before the dam was constructed, but none remain in the lake. Longnose suckers were present prior to 1966, and white suckers migrated into the lake from Battle Creek in 1960, after the water diversion pipe was installed. Suckers compete with trout for food, and are considered detrimental to trout production. In 1966, longnose suckers were successfully removed by chemical rehabilitation, and they have not been caught since. Subsequent to 1966, the white sucker population expanded, and by 1978, test netting indicated that 85% of the fish population was composed of this species. The growth of trout in Reesor Lake in 1978 was comparable to trout growth in lakes with similar sucker populations, such as Chain Lakes Reservoir, but slow compared to trout growth in lakes where there were no suckers, such as Heninger Reservoir (English 1979). White suckers were removed from Reesor Lake by chemical treatment in September 1979. At the same time, a fish barrier was built on the inlet from Battle Creek to prevent reentry of suckers to the lake. Test netting in May 1985 caught rainbow trout only (Bishop 1989), an indication that the sucker removal program and a subsequent winterkill during 1981/82 had eliminated the white sucker population. The status of the forage fish population since the 1979 chemical treatment is unknown, but sticklebacks were identified in rainbow trout stomachs in 1984 (English 1985).

A creel census was conducted by Fish and Wildlife Division between May and August in 1984 (Bishop 1985). The majority of anglers interviewed lived within 80 km of the lake, usually in the Medicine Hat area. The highest catches (0.32 trout/angler-hour) were recorded during May. The success rate improved again in August (0.23 trout/angler-hour), probably because young-of-the-year fish stocked in May had grown to a catchable size. The average catch rate for the survey period was 0.22 trout/angler-hour, and the best catches were usually made near the dock. This catch rate is considerably higher than the 0.05 trout/angler-hour catch rate calculated during a 1979 survey conducted before suckers were removed from the lake (Fitch 1981). The mean length and weight of rainbow trout taken by anglers in 1984 was 27.3 cm and 247 g, respectively (English 1985). Ninety-five percent of these fish were age 1+ years, and had grown at a rate of approximately 1.48 cm/month. This rate is similar to rates recorded in other stocked lakes in the southern region, such as Michelle and Cavan lakes, and is much higher than growth rates in nearby Spruce Coulee Reservoir (0.99 cm/month).


Birds are numerous in the Cypress Hills: more than 200 species have been sighted and about 90 species nest there. Nine species of waterfowl have been observed during summer, but the number of migrants that might use the park lakes for staging purposes is unknown. Mallards, American Widgeons and Lesser Scaup have been sighted on Reesor Lake, and small numbers of Double-crested Cormorants feed there occasionally. Great Blue Herons frequently feed among the cattails, and Belted Kingfishers have also been spotted near the water. Horned Larks are present northeast of the lake in the Cypress Hills area, and Bank Swallows are common near the lakeshore (Lombard North Group 1973). Sixteen Wild Turkeys were introduced into the Cypress Hills in 1962 and a small population has become established. Poor-wills were recorded in 1945 and can still be heard-the Cypress Hills are the only place in Alberta where they are found (Finlay and Finlay 1987).

Elk were brought to the park in 1938 to replace the original population, which had been hunted to extinction by the 1890s. The Cypress Hills area is an important wintering area for elk, mule deer and white-tailed deer. Four moose were introduced to the park in 1956, and a population has become established since that time. Moose are not thought to be native to the park, although there are some reports to the contrary. In the 1980s, the moose herd in the park numbered 60 to 70 (Finlay and Finlay 1987). Moose winter in an area northwest of the lake and in the valley bottom along Battle Creek. Beaver were brought into the park around 1940; in 1973, one beaver lodge and three muskrat houses were sighted at Reesor Lake (Lombard North Group 1973).

M.E. Bradford


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