|Map Sheets||82H/7, 8|
|Lat / Long||49.3666667, -112.5833333|
|Max depth||16.5 m|
|Mean depth||8.4 m|
|Dr. Basin Area||168 km2|
|Drainage Basin||South Saskatchewan River Basin|
|Sport Fish||Lake Whitefish, Walleye, Northern Pike|
|TP x||12 µg/L|
|CHLORO x||2.6 µg/L|
|TDS x||119 mg/L|
Milk River Ridge Reservoir is an attractive offstream reservoir located 8 km south of the town of Raymond in the County of Warner. Its deep, clear water and the pleasant surrounding scenery make it a popular spot for power boating, water skiing and angling. To reach the reservoir, take Highway 5 south from the city of Lethbridge for approximately 27 km, then drive east on Highway 52 for 6 km, south on Secondary Road 844 for about 8 km, and east on Secondary Road 506 for about 12 km. Turn north onto the access road for Ridge Park Municipal Recreation Area, located on the south shore (FIGURE 1, 2). This park is operated by the municipal district; it offers 12 campsites, pump water from a cistern, a concrete boat launch, a beach and a playground. As well, an Alberta Environment day-use area with a gravel boat launch is located on the east end of the reservoir (FIGURE 2). There are no boating restrictions over most of the reservoir, but in some posted areas all boats are prohibited, and in other posted areas power boats are restricted to a maximum speed of 12 km/hour (Alta. For. Ld. Wild. 1988).
Milk River Ridge Reservoir is named for the gently sloping ridge to the south which provides welcome relief to the flat prairie. The reservoir was built by the federal Prairie Farm Rehabilitation Administration in 1956 as an offstream storage and balancing reservoir for the St. Mary River Irrigation District (SMRID). Alberta Environment has been the owner of the reservoir and all structures since 1974 and operates them in cooperation with the SMRID. As is shown on the map in the introduction to the South Saskatchewan and Milk River basins, Milk River Ridge Reservoir is the third largest of the 12 major reservoirs in the SMRID; only St. Mary and Chin reservoirs are larger. Water enters Milk River Ridge Reservoir via a canal from St. Mary Reservoir. Most of the outflow flows north and east to supply water for irrigation and municipal and domestic use as far east as the city of Medicine Hat; a smaller outflow supplies water to areas just east of the reservoir.
Milk River Ridge Reservoir is a moderately deep, steep-sided reservoir with clear water that is attractive for recreation. Water skiing and power boating are popular on the east end and anglers eagerly seek the reservoir's very large northern pike. In 1974, a pike weighing 17 kg, an Alberta record, was taken (English 1977). There are no regulations specific to the reservoir, but provincial sport fishing regulation and limits apply (Alta. For. Ld. Wild. 1989). A commercial fishery for lake whitefish operates on the reservoir for two weeks in October each year.
The south shore of the reservoir is dissected by many coulees. The natural vegetation in the coulees provides excellent habitat for deer, grouse, pheasants and partridge, and the bays in the lake provide good habitat for waterfowl. The islands at the east end are used by nesting geese and gulls, and pelicans and cormorants can also often be seen there.
The natural drainage basin of Milk River Ridge Reservoir is about 11 times the area of the lake (Tables 1, 2). The basin is located almost entirely on the north-facing slope of Milk River Ridge (FIGURE 1), which rises almost 300 m above the reservoir to an elevation of 1,315 m. Runoff from this area flows through numerous north-draining coulees. Before the dams were built, local runoff filled two sloughs in two large east-west oriented coulees, Kipp Coulee to the west and Middle Coulee to the east. Portions of both of these coulees were flooded to form Milk River Ridge Reservoir.
The drainage basin lies in the Mixed Grass Ecoregion (Strong and Leggat 1981). Soils are primarily Dark Brown Chernozemics, which form in moderately to well-drained areas under grasslands. Regosols and Brunisols are present in imperfectly drained and seepage areas. The vegetation was originally dominated by spear, grama and wheat grasses, but now almost all of the natural grassland in the basin has been cultivated to grow wheat and other grains. Natural vegetation remains in the coulees. North-facing coulees, which support shrubs such as wild rose, saskatoon and buckbrush, and trees such as trembling aspen, provide good wildlife habitat. Cottonwood and willow grow along water courses. Most of the basin is privately owned; only a narrow strip around the shore and small area at the east end of the reservoir are Crown land.
Milk River Ridge Reservoir was created by the construction of two dams (TABLE 2, FIGURE 1). The North Ridge Dam is in the middle of the north shore and blocks the natural drainage of Kipp Coulee to Cross Coulee. The East Ridge Dam is across Middle Coulee. As well, there are several short dykes and one long dyke along the north shore near the east end. The reservoir is 17.7-km long and has a maximum width of 1.6 km. The reservoir basin drops steeply along the entire shoreline except at the west end where the slope is more gentle. There are two basins: the west one has a maximum depth of 16.5 m and the east one has a maximum depth of 14.0 m. A channel was dug along the bottom of the reservoir to facilitate flow between the basins if the reservoir had to be drawn down to its fullest extent (FIGURE 2). The total live storage at the design full supply level is 125 x 106 m3 of water.
Except for a small amount of runoff from the natural drainage basin, the inflow to Milk River Ridge Reservoir enters via a canal at the west end (TABLE 2). The water in this canal is diverted from the St. Mary, Belly and Waterton rivers to St. Mary Reservoir; it then passes through Jensen Reservoir before making its way to Milk River Ridge Reservoir. Approximately 98% of the water flows out of Milk River Ridge Reservoir via the North Ridge Dam to tiny Cross Coulee Reservoir, which acts as a balancing pond, and then to Raymond Reservoir, which lies parallel to Milk River Ridge Reservoir, about 2 km to the north. The water then snakes its way through canals and a series of reservoirs to supply water for irrigation, municipal, domestic, industrial and recreational uses as far east as Medicine Hat. The remaining 2% of the water flows out of Milk River Ridge Reservoir via the East Ridge Dam to Middle Coulee to supply local irrigation, domestic and municipal needs and to support wildlife and recreational uses.
Large volumes of water pass through Milk River Ridge Reservoir during the period that the canals are flowing, usually from mid-April to mid-October. From 1977 to 1988, the average annual volume was 688.1 x 106 m3 (Alta. Envir. n.d.[b]). The mean residence time of water in the reservoir between mid-April and mid-October is only 41.3 days (TABLE 2). In dry years, such as 1988, the demand for irrigation water is high so the flow-through volume is high and the water residence time is as little as 27 days.
The water level of Milk River Ridge Reservoir is quite variable (FIGURE 3). The reservoir is filled each spring when runoff is abundant, then water is released when demand increases in the summer. Usually, the reservoir level drops through the summer until it reaches its winter operating level. If water is available in the fall, the reservoir is filled as much as possible. Drawdown may be less than 1.8 m in some years, but in dry years such as 1977 and 1979, the demand for water is high and drawdown may exceed 6.0 m. In 1982/83, the control structures needed repair and the reservoir was drawn down as far as possible, to 13.1 m below full supply level, leaving only two small, shallow pools. The full supply level is rarely attained; approximately 0.6 m of storage is kept in reserve in case of sudden storms.
The water quality of Milk River Ridge Reservoir was examined by Alberta Environment in 1983, 1985 and 1986 (Alta. Envir. n.d.[c]).
Milk River Ridge Reservoir has well-buffered, fresh water (TABLE 3). The dominant ions are calcium and bicarbonate. The pH is low compared to that in most other Alberta lakes.
The reservoir is exposed to prevailing west winds, which continuously mix the water and prevent stratification (FIGURE 4). Dissolved oxygen concentrations probably remain high from the surface to the bottom throughout the summer (FIGURE 4). The dissolved oxygen concentration in winter has been determined only once, on 24 February 1978; the dissolved oxygen concentration was 14 mg/L just under the ice and 1.5 mg/L on the bottom (Alta. For. Ld. Wild. n.d.).
Milk River Ridge Reservoir is a nutrient-poor, oligotrophic reservoir, in contrast to natural lakes in the area. In 1986, phosphorus levels were low and varied only slightly over the summer (TABLE 4, FIGURE 5). Total phosphorus concentrations were highest when the reservoir was being filled in spring and late fall. Chlorophyll a concentrations, which were consistently very low, peaked in October at 3.2 µg/L (FIGURE 5).
There are no data on the phytoplankton or macrophytes in Milk River Ridge Reservoir.
The zooplankton in the reservoir was sampled by Fish and Wildlife Division from June to October in 1975 with a Wisconsin-style plankton net of number 20 mesh silk bolting cloth (English 1977). Densities and volumes were low compared to those in samples taken from other reservoirs in the area during the same period. Copepods were the dominant group throughout the summer; their populations peaked in June. The highest number of rotifers also occurred in June but cladocerans were most abundant in September. There is no information on benthic invertebrates in this reservoir.
Seven species of fish are known to inhabit Milk River Ridge Reservoir: walleye, northern pike, lake whitefish, longnose sucker, white sucker, burbot and spottail shiner. The sport fishery is aimed primarily at northern pike, which grow to an admirable size. Walleye have migrated naturally to the reservoir but few are caught, possibly because few anglers try for them (Bishop 1988).
Lake whitefish are the target of an annual two-week commercial fishery each October. This species is indigenous to the reservoir, but adult fish were stocked in 1959 and 1960 to hasten development of a commercial fishery, which began in 1968 (Clements 1974). Sixteen licences were issued in the 1987/88 season. The total annual catch averaged 6,251 kg between 1968 and 1987 (excluding the 1983/84 and 1984/85 seasons). The species composition of this catch was 86% lake whitefish, 14% northern pike and less than 1% walleye (Alta. For. Ld. Wild. n.d.). Lake whitefish spawn in shallow water in the fall. The severe drawdown for repairs to the control structures in 1982/83 decimated the entire lake whitefish population. Only one lake whitefish was caught by test netting in 1984 (Alta. For. Ld. Wild. n.d.) and the commercial fishery was poor for several years. Lake whitefish move throughout the irrigation system, however, so restocking was not necessary and the commercial fishery had recovered by 1986 (Bishop 1988).
Milk River Ridge Reservoir provides important habitat for waterfowl. The reservoir is a regionally significant nesting area for Canada Geese; most nesting occurs on the islands at the east end (Butler Krebes Assoc. Ltd. 1978). Gulls nest on the islands as well, and pelicans and cormorants rest on the islands during feeding forays. The reservoir is also an important waterfowl staging area for fall migration.
The coulees on the slope south of the reservoir provide prime habitat for mule deer and white-tailed deer, and refuge areas for antelope. Coulees provide excellent habitat for upland game birds such as Hungarian Partridge, Ring-necked Pheasants and Sharp-tailed Grouse.
Agriculture Canada. 1957. Topographic plan, Milk River Ridge Reservoir. Prairie Farm Rehabilitation Admin., Eng. Br., Ottawa.
Alberta Environment. n.d.[a]. Devel. Op. Div., Dam Safety Br. Unpubl. data, Edmonton.
-----. n.d.[b]. Devel. Op. Div., Irrig. Headworks Br. Unpubl. data, Edmonton.
-----. n.d.[c]. Envir. Assess. Div., Envir. Qlty. Monit. Br. Unpubl. data, Edmonton.
-----. n.d.[d]. Tech. Serv. Div., Hydrol. 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.
Bishop, F. 1988. Alta. For. Ld. Wild., Fish Wild. Div., Lethbridge. Pers. comm.
Butler Krebes Associates Ltd. 1978. Milk River Ridge Reservoir - Area development plan: Phase I and II, inventory and analysis. Prep. for Alta. Envir., Plan. Div., Edmonton.
Clements, S.M. 1974. The history and management of the fishery resource of Milk River Ridge Reservoir. Alta. Ld. For., Fish Wild. Div., Lethbridge.
Energy, Mines and Resources Canada. 1975. National topographic series 1:50000 82H/7 (1975), 82H/8 (1975). Surv. Map. Br., Ottawa.
English, W.E. 1977. A limnological survey of Milk River Ridge Reservoir. Alta. Rec. Parks Wild., Fish Wild. Div., Lethbridge.
Environment Canada. 1976-1987. Surface water data. Prep. by Inland Waters Directorate. Water Surv. Can., Water Resour. Br., Ottawa.
-----. 1982. Canadian climate normals, Vol. 7: Bright sunshine (1951-1980). Prep. by Atm. Envir. Serv. Supply Serv. Can., Ottawa.
Strong, W.L. and K.R. Leggat. 1981. Ecoregions of Alberta. Alta. En. Nat. Resour., Resour. Eval. Plan. Div., Edmonton.