Little Bow Lake Reservoir

Basic Info
Map Sheets82I/2
Lat / Long50.2000000, -112.6666667
50°12'N, 112°40'W
Area5.44 km2
Max depth11 m
Mean depth4.3 m
Dr. Basin Area37.6 km2
Dam, WeirDam
Drainage BasinOldman River Basin
Camp GroundNone
Boat LaunchPresent
Sport FishRainbow Trout, Yellow Perch, Brown Trout, Northern Pike, Lake Whitefish
Trophic StatusOligotrophic-Mesotrophic
TP x14 µg/L
CHLORO x2.1 µg/L
TDS x215 mg/L
119
Photo credit: unknown

Introduction

Little Bow Lake Reservoir is a small, off-stream reservoir located in the County of Vulcan, 50 km southeast of the town of Vulcan and 180 km southeast of the city of Calgary. Although the reservoir is in the Oldman River drainage basin, most of its water is diverted to it from the Bow River basin. To reach the reservoir from Calgary, drive south and east on Highway 24 to the village of Champion. Turn east onto Secondary Road 529 and drive for 30 km, then drive south on Secondary Road 845 for about 3.5 km. Turn onto a local road that provides access to a small day-use area at a beach near the main dam (FIGURE 1, 2). There are no campgrounds at the reservoir, but the day-use area, which was built in 1978 by Alberta Environment, includes a boat launch and provides the best access to the water. Federal boating regulations and provincial sport fishing regulations apply to Little Bow Lake Reservoir, but there are no additional boating or fishing regulations specific to the reservoir (Alta. For. Ld. Wild. 1988; 1989).

Little Bow Lake Reservoir is situated in a depression surrounded by short grass prairie. For many centuries, members of the Blackfoot, Blood and Peigan tribes traversed the region, following vast herds of buffalo (IEC Beak Consult. Ltd. et al. 1983). Homesteaders settled in the area by 1907, and soon fenced the open range. Grain farming became the primary land use. By 1920, the Canada Land and Irrigation Company had completed construction of both McGregor Lake and Little Bow Lake Reservoir. Large volumes of water were brought by canal from the Bow River near Carseland to McGregor Lake, the water then flowed through 20 km of canal to Little Bow Lake Reservoir, then canals took the water further east to provide water for irrigation. In 1954, Travers Reservoir was built, providing more storage volume and replacing most of the canal between McGregor Lake and Little Bow Lake Reservoir. All three reservoirs and the connecting canals are now owned and operated by Alberta Environment as part of the Carseland-Bow River Headworks System that stores and delivers water for the Bow River Irrigation District to supply water for irrigation and to support multi-purpose water use.

Little Bow Lake Reservoir has very clear water and is locally popular for swimming, sport fishing, power boating and sailing. It also supports a small commercial fishery for lake whitefish. The reservoir has good recreation potential because of its excellent water quality and natural beaches; however, exposure to strong winds and the growth of aquatic plants limit some forms of recreation (Richard Strong Assoc. Ltd. 1983; R.L. & L. Envir. Serv. Ltd. 1985). There are no cottages around the reservoir.

Drainage Basin Characteristics

The natural drainage basin is small, only seven times the reservoir's surface area (Tables 1, 2). The watershed is part of an area with the lowest rainfall and highest evaporation in Canada. The drainage basin has porous soils and produces little natural runoff. The land is part of a flat to gently rolling glacial till plain located in the Short Grass Ecoregion (Strong and Leggat 1981). The natural vegetation, which is typical of short grass prairie, is dominated by grama and spear grasses. Trembling aspen, eastern cottonwood and willows grow along water courses, and buckbrush and wolf willow grow in depressions and coulees. Soils are predominantly Brown Chernozemics (Strong and Leggat 1981; Richard Strong Assoc. Ltd. 1983). There are some oil and gas wells in the drainage basin, but no major population centres. The land around the reservoir is all Crown land, and most of it is leased for cattle grazing.

Little Bow Lake Reservoir is the furthest downstream of a series of three reservoirs that store water for the Bow River Irrigation District (FIGURE 1, inset). The two others, McGregor Lake and Travers Reservoir, are much larger and provide the major portion of water storage capacity. Although Little Bow Lake Reservoir is considered an off-stream reservoir as it is not on any natural stream, it does have a large volume of water diverted through it from April to October. Except for an insignificant amount of inflow from rain and runoff from the natural drainage basin, all of the water in Little Bow Lake Reservoir comes from Travers Reservoir. In turn, Travers Reservoir receives approximately 90% of its inflow from the Bow River via McGregor Lake (Envir. Can. 1987). The remaining 10% of the water in Travers Reservoir comes from the Little Bow River, which receives about 90% of its inflow from water diverted from the Highwood River near the town of High River. Of the water entering Travers Reservoir, 3% flows over the spillway to maintain flow in the Little Bow River and 97% is diverted to Little Bow Lake Reservoir (Envir. Can. 1987).

Lake Basin Characteristics

Little Bow Lake Reservoir was built with a design full supply level of 855.42 m (TABLE 2) and was operated close to that level until Travers Reservoir was built in 1954. Travers Reservoir was built with a full supply level of 856.18 m, which was not sufficiently higher than Little Bow Lake Reservoir to provide ample hydraulic head to move water quickly. Consequently, the operating full supply level of Little Bow Lake Reservoir was dropped almost 2.59 m, to 852.83 m. The canal from Travers Reservoir flows through a concrete chute into the southwest corner of Little Bow Lake Reservoir (FIGURE 1). Part of the abandoned 1920 canal, which flowed from McGregor Lake into the northwest corner of Little Bow Lake Reservoir, is still visible. Little Bow Lake Reservoir now acts as a balancing rather than as a storage reservoir; therefore, its level is much more stable than the two upstream storage reservoirs. The details of the main dam are presented in TABLE 2. There are also four small "saddle dams" at the design full supply level on coulees on the perimeter, but these are now grass-covered and hard to discern.

The only outlet from Little Bow Lake Reservoir is in the main dam, which releases water into a canal that soon branches into the Lomond Lateral Canal and the Bow River Irrigation District Main Canal. All flow, both in and out of the reservoir, occurs between late April and mid-October (TABLE 2). The reservoir's volume is replaced 16 times per summer, a very high rate of exchange compared to natural lakes and most storage reservoirs.

The shape of Little Bow Lake Reservoir is quite different from that of upstream McGregor Lake and Travers Reservoir, as it fills a gently sloping, rectangular depression rather than a long, narrow, steeply sloping glacial meltwater channel. The bathymetric map (FIGURE 2) was drawn for the reservoir's original design full supply level, almost 3 m above current levels. Because 30% of Little Bow Lake Reservoir is less than 2-m deep (FIGURE 3), the reservoir is very sensitive to major water level fluctuations. Under present operation, however, a stable level is maintained-from 1975 to 1987, annual fluctuations averaged 0.25 m (FIGURE 4).

One consequence of the gently sloping lake bottom and stable water level is that the nearshore areas support extensive weed beds (MacNeill 1978; Richard Strong Assoc. Ltd. 1983). However, strong prevailing westerly winds have created natural sand beaches in some areas, such as by the Alberta Environment day-use area on the east shore.

Water Quality

The water of Little Bow Lake Reservoir was sampled by Alberta Environment biweekly from May until October in 1983 and 1984 (Alta. Envir. n.d. fb]).

The attractive, clear water of the reservoir is a consequence of both its source (primarily the Bow River) and the retention of some suspended material and nutrients in upstream reservoirs (McGregor and Travers). The water chemistry of Little Bow Lake Reservoir is also similar to that of its source; conductivity, alkalinity and total dissolved solids are all low and the dominant ions are bicarbonate, sulphate and calcium (TABLE 3).

Little Bow Lake Reservoir is well-mixed during the summer because it is exposed to prevailing westerly winds. Consequently, temperatures were uniform throughout the water column from April through October in 1984 (FIGURE 5). Dissolved oxygen remained high from surface to bottom during this period (FIGURE 6). No data have been collected in winter, but dissolved oxygen levels must be sufficient for fish, since no winterkills have been reported (Alta. For. Ld. Wild. n.d.).

The mean total phosphorus (14 µg/L) and chlorophyll a (2.1 µg L) concentrations during the open-water season (TABLE 4) are similar to those in Travers Reservoir and are low compared to natural lakes in the area. Chlorophyll a concentrations were steady throughout the summer of 1984, with a maximum of 5 µg/L in October (FIGURE 7). The fall maximum in Little Bow Lake Reservoir closely followed a September increase to 5.2 µg/L in Travers Reservoir. The trophic status of Little Bow Lake Reservoir is on the border between oligotrophic and mesotrophic.

Biological Characteristics

Plants

There are no data on the algae in Little Bow Lake Reservoir, nor are there data on macrophytes except for reports of weedy areas along the shore (MacNeill 1978; Richard Strong Assoc. Ltd. 1983).

Invertebrates

The zooplankton in the reservoir was studied monthly from June until October in 1975 (English 1977). The density of zooplankton was highest in June (2.92 mL/L), when rotifers were dominant, and in July (2.91 mL/L), when copepods were dominant. The density decreased to 0.29 mL/L in August, then increased to 1.15 mL/L in October, when rotifers again were dominant.

The only record of benthic invertebrates is from a 1964 study (MacNeill 1978). Samples were taken from three sites once a month from May to August. Midge larvae (Chironomidae) dominated (by number), except in June, when more clams (Pelecypoda) were found. Scuds (Amphipoda) and aquatic earthworms (Oligochaeta) were also numerous.

Fish

Ten species of fish have been found in Little Bow Lake Reservoir (Alta. For. Ld. Wild. n.d.; MacNeill 1978). Lake whitefish, northern pike, burbot, longnose suckers and white suckers are the most abundant. Rainbow trout are present but, as they cannot spawn in Little Bow Lake Reservoir, the population depends on migration from Travers Reservoir. Spottail shiners and yellow perch are present, and shorthead redhorse and brown trout are rarely captured. No fish have been stocked in the reservoir. Therefore, those present are either descendants of fish that migrated from McGregor Lake before 1954, or descendants of fish that migrated from Travers Reservoir since 1954. High water velocities through irrigation structures in and out of Little Bow Lake Reservoir prevent fish from moving from Little Bow Lake Reservoir back to Travers Reservoir, or from returning to Little Bow Lake Reservoir once they go through the outlet structure.

Little Bow Lake Reservoir supports a modest sport fishery for northern pike and rainbow trout and a commercial fishery for lake whitefish. There are no catch data for the sport fishery. The commercial fishery has operated since 1948/49; 90% of the catch is lake whitefish. An annual quota of 11,300 kg of whitefish has been in effect since 1968. The annual catch from the 1983/84 season to the 1985/86 season averaged 17,897 kg of lake whitefish, 242 kg of northern pike, 32 kg of suckers, 21 kg of burbot and 15 kg of trout-an average total catch of 18,207 kg/year (Alta. For. Ld. Wild. n.d.; IEC Beak Consult. Ltd. et al. 1983). TABLE 5 gives the average annual growth rates of lake whitefish in Little Bow Lake Reservoir for the period from 1957 to 1978. Growth rates were more rapid than those in McGregor Lake or Travers Reservoir.

Wildlife

There is little information on the wildlife using Little Bow Lake Reservoir. The reservoir's stable water level, crenate shoreline and many islands provide important nesting areas for geese, gulls and cormorants (Markham 1978; Richard Strong Assoc. Ltd. 1983).

J.M. Crosby

References

Alberta Environment. n.d.[a]. Devel. Op. Div., Irrig. Headworks Br. Unpubl. data, Edmonton.

-----. n.d.[b]. Envir. Assess. Div., Envir. Qlty. Monit. Br. Unpubl. data, Edmonton.

-----. n.d.[c]. Tech. Serv. Div., Hydrol. Br. Unpubl. data, Edmonton.

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

-----. n.d.[e]. Water Resour. Mgt. Div., Dam Safety Br. Unpubl. data, Edmonton.

Alberta Forestry, Lands and Wildlife. n.d. Fish Wild. Div. Unpubl. data, Edmonton.

-----. 1988. Boating in Alberta. Fish Wild. Div., Edmonton.

-----. 1989. Guide to sportfishing. Fish Wild. Div., Edmonton.

Alberta Research Council. 1972. Geological map of Alberta. Nat. Resour. Div., Alta. Geol. Surv., Edmonton.

Canada Land and Irrigation Company. 1914. McGregor Reservoir, Plan. No. 1042. Can. Ld. Irrig. Co., Calgary.

Energy, Mines and Resources Canada. 1976, 1977. National topographic series 1:50000 82I/7 (1976), 82I/2 (1977). Surv. Map. Br., Ottawa.

English, W.G. 1977. A limnological survey of Little Bow Reservoir. Alta. Rec. Parks Wild., Fish Wild. Div., Lethbridge.

Environment Canada. 1982. Canadian climate normals, Vol. 7: Bright sunshine (1951-1980). Prep. by Atm. Envir. Serv. Supply Serv. Can., Ottawa.

-----. 1987. Historical streamflow summary, Alberta. Water Surv. Can., Water Resour. Br., Ottawa.

IEC Beak Consultants Ltd., Techman Engineering Ltd. and Aresco Ltd. 1983. Environmental overview of the Little Bow River basin. Prep. for Alta. Envir., Plan. Div., Edmonton.

MacNeill, J.W. 1978. A review of the history and management of the fishery resource of Little Bow Reservoir. Alta. Rec. Parks Wild., Fish Wild. Div., Edmonton.

Markham, B.J. 1978. Status of the Double-crested Cormorant (Phalocrocorax auritus) in Canada. Prep. for Commit. on the Status of Endangered Wild. in Can. by Alta. Rec. Parks Wild., Fish Wild. Div., Edmonton.

Richard Strong Associates Limited. 1983. McGregor, Travers, Little Bow Reservoir vicinity recreation development study. Prep. for Alta. Envir., Plan. Div., Edmonton.

R. L. & L. Environmental Services Ltd. 1985. A compendium of existing environmental data on Alberta reservoirs. Prep. for Alta. Envir. Res. Trust, Edmonton.

Strong, W.L. and K.R. Leggat. 1981. Ecoregions of Alberta. Alta. En. Nat. Resour., Resour. Eval. Plan. Div., Edmonton.


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