Tyrrell Lake

Basic Info
Map Sheets82H/8
Lat / Long49.3833333, -112.2666667
49°22'N, 112°16'W
Area3.99 km2
Max depth6.1 m
Mean depth3.8 m
Dr. Basin Area122 km2
Dam, WeirDam
Drainage BasinSouth Saskatchewan River Basin
Camp GroundNone
Boat LaunchPresent
Sport FishRainbow Trout, Northern Pike, Lake Whitefish
Trophic StatusNo Data
TP x150 µg/L
CHLORO xNo Data µg/L
TDS x7,450 mg/L
Photo credit: unknown


Tyrrell Lake is an elongate, saline lake lying in a shallow coulee on flat plains. It is located 45 km southeast of the city of Lethbridge in the County of Warner. To reach the lake from Lethbridge, drive southwest on Highway 4 until you are 3 km past the hamlet of New Dayton. Watch for signs and turn east onto a secondary road and drive for 1.5 km to a county-operated day-use site at the northwest end of the lake (FIGURE 1, 2). The facilities include a concrete boat launch, a fish cleaning stand, picnic tables and toilets. There is also a day-use site at the south end of the lake; few facilities are provided and the boat launch is quite muddy.

Tyrrell Lake was named for Joseph Burr Tyrrell, a member of the Geological Survey of Canada from 1880 to 1897 (Wrentham Hist. Soc. 1980). The lake is located on the mixed-grass plains, an area that once supported enormous herds of buffalo. The lake was a campsite for Indians when they travelled between the Cardston area and Montana (Warner Old Timers' Assoc. 1962). In the early 1900s, a wave of settlers came to farm the area, and in 1909, the Tyrrell Lake School was built near the southwest shore of the lake (Wrentham Hist. Soc. 1980).

Tyrrell Lake is a natural water body, but historically, the water level has fluctuated greatly. During the dust-bowl years of the 1930s, the lake reputedly became a dry mud flat (Fitch 1980). In the early 1950s, a canal was built from Milk River Ridge Reservoir via Middle Coulee to Tyrrell Lake to help stabilize levels. However, drainage near the lake was still inadequate, so in wet years farmland was flooded; during prolonged droughts the water level of the lake and associated marshes dropped and jeopardized valuable waterfowl habitat. In 1985, the Tyrrell-Rush complex became the first Wetlands for Tomorrow project built in Alberta. Joint funding was provided by Alberta Environment, Ducks Unlimited (Canada) and Fish and Wildlife Division. The County of Warner and the St. Mary's River Irrigation District (SMRID) provided enthusiastic cooperation. The canals and structures that were built have allowed water levels to be stabilized in Tyrrell Lake, in nearby Rush Lake and in a large marshland south of Rush Lake to form a major wetland area in a region where waterfowl habitat is scarce and drought is common. Agricultural interests are met because the project included an efficient drainage system to move excess runoff from farmland and direct it into the improved Rush Lake drain, which conveys water to Etzikom Coulee (inset, FIGURE 1).

Tyrrell Lake is nutrient rich and supports occasional algal blooms. These blooms and the muddy lake bottom discourage swimming. In posted areas of the lake, power boats are restricted to maximum speeds of 12 km/hour (Alta. For. Ld. Wild. 1988). Because of high salinity, the only native fish species are salt-tolerant minnows. However, the lake is stocked annually with rainbow trout, which exhibit one of the fastest growth rates in North America and provide an excellent sport fishery. Fishing with bait fish is not permitted (Alta. For. Ld. Wild. 1989). The lake is also known for its population of tiger salamanders, although their numbers have been severely reduced since the introduction of trout.

Drainage Basin Characteristics

The drainage basin of Tyrrell Lake is large (122 km2, TABLE 1) and covers an area almost 31 times the size of the lake (3.99 km2, TABLE 2). The watershed is part of the Mixed Grass Ecoregion (Strong and Leggat 1981). The land is flat, but it is dissected by coulees that were formed as glacial outwash channels. Rainfall is scarce (TABLE 1), the soil is porous, and the evaporation rate is double that of precipitation. Trembling aspen and shrubs such as willow, buckbrush, snowberry and saskatoon can survive only on seepage sites or on the north-facing slopes of coulees or river valleys. The soils are Orthic Brown and Dark Brown Chernozemics (Bertrand 1974). Most of the land has been cultivated for grain and forage crops, but there are some areas of native vegetation around the lake (Wentz 1974).

The hamlet of New Dayton is the only population centre in the drainage basin. Most of the land surrounding the lake is privately owned. There are no cottages near the lake, but there is an intensive livestock operation on the south shore (Fitch 1980).

Water enters Tyrrell Lake naturally through runoff, either from precipitation or from irrigation return flows. Runoff flows through Suds Lake, an intermittent water body, then into the north end of Tyrrell Lake. Additionally, water is released from Milk River Ridge Reservoir, flows through Middle Coulee and is diverted into the south end of Tyrrell Lake (FIGURE 1). Water also leaves Tyrrell Lake from the south end, flows into a wetland, then into Rush Lake (FIGURE 1) or north to Etzikom Coulee and east to Pakowki Lake, a large intermittent lake with no outlet.

Lake Basin Characteristics

Tyrrell Lake is fairly long (5 km), narrow (1.2 km at the widest point), and shallow (TABLE 2). Like other shallow, saline lakes in southern Alberta, the lake basin slopes gently to a flat, central area. The area deeper than 5.5 m occupies approximately one-third of the lake area (FIGURE 2). Most of the lake bottom is soft mud.

Prior to the 1950s, the water level of Tyrrell Lake showed extreme fluctuations; the lake was completely dry in the thirties (Fitch 1980). In the 1950s, the provincial government built the Tyrrell Lake Supply Canal to bring water to the lake from Milk River Ridge Reservoir via Middle Coulee. This project helped to stabilize lake levels in dry years, but drainage from the Tyrrell-Rush Lake area in wet years still continued to be inadequate, and over 2,300 acres (931 ha) of farmland were flooded in wet springs. Another concern was that nearby Rush Lake and its associated marshes, which provided the best waterfowl habitat in southern Alberta, were jeopardized during droughts (Alta. Envir. 1982). The construction of canals and dykes began in 1983 and was completed in 1986. It is now possible to bring up to 1.85 x 106 m3 of water each year from Milk River Ridge Reservoir to Tyrrell Lake, then to Rush Lake (Fitch 1988). The extremely low water levels in Tyrrell Lake from 1984 to 1986 (FIGURE 3) were the result of construction activities and natural drought. Construction was completed in 1987 and diversion to the lake began that year; the lake was still filling in 1988.

Water Quality

The water quality in Tyrrell Lake was monitored in 1977 and 1978 by Fish and Wildlife Division (Fitch 1980) and in 1983 by Alberta Environment (Alta. Envir. n.d.[a]).

Tyrrell Lake has clear, saline water. The dominant ions are sulphate and sodium (TABLE 3). The concentration of total dissolved solids (a measure of salinity) varies inversely with water level: in 1977, the water level was relatively low (FIGURE 3) and the concentration was 6,090 mg/L; in 1978, the water level was higher and the concentration was 4,824 mg/L; and in 1983, the water level was slightly lower than that recorded in 1977, and the concentration of total dissolved solids was 7,062 mg/L.

Tyrrell Lake is exposed to strong winds, which likely keep it well-mixed all summer; the water column was isothermal and well-oxygenated in June and September 1983 (FIGURE 4). In 1977, however, dissolved oxygen concentrations in July declined to between 2.5 and 3.5 mg/L throughout the lake. These low concentrations may have resulted from the decay of a blue-green algal bloom. In February 1978, some oxygen depletion occurred toward the bottom, but the dissolved oxygen concentration in the top 2 m was 8 mg/L and sufficient for fish survival (FIGURE 4). In some years, winter dissolved oxygen concentrations drop to 4 mg/L at the surface. There are no data for oxygen concentrations at the bottom, but they are likely close to zero.

Tyrrell Lake is nutrient-rich (TABLE 4). Although the high salinity likely inhibits algal growth (Bierhuizen and Prepas 1985), blooms of blue-green algae occasionally do occur. Algae was reported to form a "coppery-green crust" at the south end of the reservoir in 1960 (Paterson 1960). Chlorophyll a concentrations in Tyrrell Lake have not been monitored. Consequently, it is not possible to categorize the lake's trophic status.

Biological Characteristics


The algal bloom noted in 1960 was dominated by the blue-green alga Microcystis; the green alga Spirogyra was also noted (Paterson 1960). Recent information on algae is not available.

Macrophytes form a narrow band around the lake, but despite extensive shallow areas, the abundance of aquatic plants is limited, likely because of high salinity. Salt-tolerant Sago pondweed (Potamogeton pectinatus) was the dominant macrophyte observed during studies by Fish and Wildlife Division in 1977 and 1978 (Fitch 1980).


The zooplankton was sampled by Fish and Wildlife Division in 1977 and 1978 (Fitch 1980). Although species diversity was low, abundance was high. Numerically, the community was dominated by Copepoda (72%), mainly Diaptomus sicilis, followed by Cladocera (25%), mainly Daphnia pulicaria and Rotifera (3%). Fairy shrimp (Branchinecta coloradensis) were recorded in Tyrrell Lake in 1978 (MacNeill 1979). This species is tolerant of saline water but is usually not present with planktivorous fish such as trout.

Benthic invertebrates were sampled by Fish and Wildlife Division in October 1977 (Fitch 1980). The total biomass (60.2 g/m2 wet weight), which was dominated by midge larvae (Chironomidae), was the third highest of 25 southern Alberta lakes.


In the 1960s, tiger salamanders (Ambystoma tigrinum) were very abundant in Tyrrell Lake (Paterson 1960). In October 1962, approximately 250 kg of larval salamanders were captured in one day (Alta. For. Ld. Wild. n.d.). That year, rainbow trout were stocked in the lake and the population of salamanders, a favourite prey of trout, started to decline. Only one salamander was caught in a 1973 test netting and for several years it was assumed that the population had been eliminated. In 1988, however, several salamanders were caught in test nets (Fitch 1988).


Tyrrell Lake is the most saline lake in Alberta stocked with rainbow trout by Fish and Wildlife Division. The growth rates of the rainbow trout are among the most rapid in North America and the fish of Tyrrell Lake have been the subject of numerous studies (Alta. For. Ld. Wild. n.d.; Haugen 1970; Radford and Clements 1971; MacNeill 1979; Fitch 1980).

Prior to 1950, when Tyrrell Lake was a natural body of water, the only species of fish in it were salt-tolerant species: fathead minnows and brook sticklebacks (Paterson 1960; Fitch 1980). Since 1950, when water diversion to Tyrrell Lake from Milk River Ridge Reservoir began, burbot, white suckers and lake whitefish have been found in small numbers; northern pike, lake chub and longnose suckers have been collected only once (Fitch 1980). Only adults of these species have been found, as they cannot spawn successfully in saline water. In test netting from 1968 to 1978, 95% to 100% of the catch was rainbow trout (Fitch 1980). A creel census in 1982 found that, in 394 angler-hours of angling, 66 trout and 9 suckers were caught (Bishop 1989).

Rainbow trout were first stocked in 1962, then 4 more times until 1973, and annually since 1974 (except in 1981 and 1986). An average of 400,000 fingerlings are introduced each year the lake is stocked (Alta. Ld. For. 1962-1974; Alta. Rec. Parks Wild. 1975-1978; Alta. En. Nat. Resour. 1979-1985; Alta. For. Ld. Wild. 1986-1987). The repeated stockings are necessary due to the low survival rate-less than 1% of the trout survive their first winter (Fitch 1980).

A comparison of the length and weight of rainbow trout stocked in 15 southern Alberta lakes showed that trout in Tyrrell Lake were consistently the longest and heaviest. By autumn, trout age 0+ years from Tyrrell Lake had a fork length of 269 mm and weighed 320 g. This was approximately 4 times heavier than the average trout from 14 other lakes. By age 1+, the average trout weighed 1.5 kg. At ages 1+, 2+ and 3+ the average weight of trout in Tyrrell Lake was 5 times heavier than that from 14 other lakes (Fitch 1980). The growth rate of Tyrrell Lake trout is among the highest in North America and reaches the maximal growth rate for the species (Fitch 1980). Although there is some variability in growth rate from year to year (TABLE 5), it is consistently exceptional.

The reason for low overwinter survival of trout in Tyrrell Lake is uncertain. One possibility is that, although winter dissolved oxygen concentrations in the lake are usually within the range considered to be sufficiently high for trout survival (over 4 mg/L), very fast-growing fish may require higher dissolved oxygen concentrations. The fast-growing trout in Tyrrell Lake are heavy for their length and have condition factors near 2.0 and therefore have lower gill area to body volume ratios than slower-growing fish with condition factors of 1.3 to 1.5. Thus, higher dissolved oxygen concentrations may be required to maintain even minimal oxygen supply to the tissues (MacNeill 1979).


The Tyrrell-Rush Lake complex is an important spring and fall staging area for waterfowl. The Rush Lake area is also important for waterfowl production (2,000 birds per year) and is likely to become even more productive now that water management structures are in place. Ducks Unlimited (Canada) have further improved habitat in the Rush Lake complex by building rock and earth islands for waterfowl and goose nesting, and by managing upland areas for waterfowl and ungulates (Schmidt 1988).

J.M. Crosby


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