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. In 2013, the lake reached record high water levels and probably exceeded 14,000 hectares. 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, seaside heliotrope (Heliotropium curassavicum) that thrives in salty soil is found here. In 1989, Ducks Unlimited (DU) constructed a number of dykes in the east end of Whitewater Lake, creating basins that attempted to stabilize water levels for nesting and migrating waterfowl; these were largely destroyed by the high water of 2011 and 2013 The observation mound remains, but vehicle access is not possible. The northwest portion of the IBA includes an area of agricultural land with potholes and ephemeral wetlands that temporarily flood in high water years.
Whitewater Lake IBA is a key area for waterfowl and shorebirds during both spring and fall migrations, and an important breeding area for several species. 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. Even higher numbers were observed in the early 2000’s. Collections of shorebirds dead from botulism in 1998 revealed that Pectoral Sandpipers and Lesser Yellowlegs were the most common species present. Significant concentrations of shorebirds counted here includes: White-rumped Sandpiper (10,000, spring 1988), Pectoral Sandpiper (2,500, August 2014); Short-billed Dowitcher (4,175, August 2016), Long-billed Dowitcher (2,196, August 2017); Buff-breasted Sandpiper (67, August 2015); American Avocet (3,279, August 2016); Stilt Sandpiper (985, August 2017); Least Sandpiper (1,250, August 2007) and; Semipalmated Sandpiper (1,800, June 1985).
Various waterbirds nest here in significant numbers. Franklins Gulls nest here in globally significant numbers; an Environment and Climate Change Canada survey in 2007 estimated that over 184,000 Franklin’s Gulls were present in multiple colonies on the lake, more than 18% of the estimated global population. 2,739 Eared Grebes were nesting during the same survey. In August 2017, 4,098 Western Grebes were counted on a single day in August. Eighty-five pairs of Black-crowned Night Herons have been recorded here as do good concentrations of other long-legged wading birds, including White-faced Ibis, Great Egret, Cattle Egret and Snowy Egret. Over 80,000 swallows have been recorded in the IBA during fall migration.
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. Also, up to 2,000 Tundra Swans have been recorded in November; this is about 1% of the North American population of the species. The lake is also used by several geese species, coots and ducks as a spring staging area. A total of 1,691 American White Pelicans were counted in August 2016.
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 have attempted to solve this problem. Ducks Unlimited also constructed a number of dykes to create enclosed cells and, because of this, the lake was less susceptible to drought. The droughts of past years that occurred may have been the reason behind the numbers of nesting birds in the surrounding ponds. However, the exceptionally high-water levels experienced more recently resulted in the DU dykes bursting in many places and the system of cells are no longer functioning.
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 and following the record high water levels between 2013 and 2016, the pressure to establish this has increased. Stabilisation of water levels has been responsible for loss of emergent vegetation in other major Manitoban wetlands and therefore such a development might have major implications for the significant congregations of migrating and breeding birds at Whitewater Lake.
DU, Manitoba Sustainable Development and the Turtle Mountain Conservation District previously developed several viewing sites around the lake but these were washed away following record high water levels. There are a number of locations where the birds of Whitewater Lake can be viewed, primarily along road allowances.
Menaces Potencielles ou Existantes
Status de Protection