Whitewater Lake (MB015)
Altitude 457 - 460m
Description du site
The Whitewater Lake catchment basin is located in the southwestern corner of Manitoba, north of Turtle Mountain Provincial Park. It is an alkaline lake that may contain no water for two or three years at a time during dry cycles; during normal years it covers 6,070 hectares, but can be as high as 10,320 hectares (and two metres deep) during years with increased run-off. Over the past 100 years there have been several decades, such as the 1930s and 1980s, in which the lake was dry most of the time. Several small creeks drain into Whitewater Lake, but there is no major natural outlet. The flat terrain surrounding the lake is used for agricultural production. A small rare herbaceous plant (Heliotropium curassavicum) is found here. At the east end of the lake, Ducks Unlimited (DU) have constructed a number of dykes, creating basins that attempt to stabilize water levels for nesting and migrating waterfowl.
Up to a quarter of a million geese and ducks have been recorded at Whitewater Lake during fall migration. Many of these birds were Snow Geese, while many others were migrating ducks of several species. About 7% of the Mid-continent population of Snow Geese consistently pass through the Whitewater Lake area in the fall. Also, up to 2,000 Tundra Swans have been recorded in November; this is about 2% of the eastern population of the species. The lake is also used by several geese species, coots and ducks as a spring staging area.
Periodically, when the lake levels are low, the largest shorebird concentrations in southern Manitoba occur on this lake, with up to 23,068 shorebirds observed in the spring of 1987. An impressive 10,000 White-rumped Sandpipers were seen here in 1988; this is 2.5% of the known winter population of the species. Collections of shorebirds dead from botulism in 1998 revealed that Pectoral Sandpipers and Lesser Yellowlegs were the most common species present.
Various waterbirds nest here in significant numbers. Eighty-five pairs of Black-crowned Night Herons have been recorded here. This figure represents 1.7% of the estimated Canadian population for this species. Franklins Gulls nest here in globally significant numbers, with over 3,000 pairs, which is over 1% of the estimated North American population. Also, over 350 Eared Grebes pairs nest at this site. Numerous other wetland and upland prairie species nest at Whitewater Lake and the surrounding area.
Enjeux de conservation
Whitewater Lake is susceptible to botulism outbreaks, such as in 1996 when an outbreak killed about 116,000 waterfowl and other waterbirds; Ducks Unlimited and other agencies are attempting to solve this problem. Ducks Unlimited have also constructed a number of dykes to create enclosed cells and, because of this, the lake is now less susceptible to drought. The droughts of recent years that have occurred may be the reason behind the lower numbers of nesting birds in the surrounding ponds.
The lake itself is designated a Wildlife Management Area under provincial regulations, so it is afforded a measure of protection. Beyond the lake, the grazing of geese in agricultural fields is of some concern to local farmers. Some farmers would like to have an outlet for the lake established, but this is not favoured by DU who have had a long-term interest in the area. DU, Manitoba Conservation and the Turtle Mountain Conservation District have developed several viewing sites around the lake.
Menaces Potencielles ou Existantes
Status de Protection