Lake Diefenbaker[2] is a reservoir and bifurcation lake in the southern part of the Canadian province of Saskatchewan. It was formed by the construction of Gardiner Dam and the Qu'Appelle River Dam across the South Saskatchewan and Qu'Appelle Rivers respectively. Construction began in 1959 and the lake was filled in 1967. The lake is 225 kilometres (140 mi) long with approximately 800 kilometres (500 mi) of shoreline. It has a maximum depth of 66 metres (217 ft), while the water levels regularly fluctuate 3–9 metres (9–27 feet) each year. The flow of the two rivers is now regulated with a considerable portion of the South Saskatchewan diverted into the Qu'Appelle. Prior to the dams' construction, high water levels in the South Saskatchewan would frequently cause dangerous ice conditions downstream in Saskatoon while the Qu'Appelle would frequently dry up in the summer months.
The lake's sandy beaches provide appropriate habitat for the nationally endangered piping plover.
The long stretches of open water and poorly consolidated shore materials makes the shores vulnerable to erosion. Between 1968 and 1992 bank recession rates have commonly ranged up to 3 metres (9.8 ft) a year with higher rates in exposed areas.
Galloway and Miry Bay (SK006) is located at the western end of the lake about 20 kilometres (12 mi) north of Cabri. The IBA site includes the shoreline and spans the width of the lake covering an area of 59.48 km2 (22.97 sq mi). Miry Bay[12] is located on the western shore and Galloway is on the eastern shore about 5 kilometres (3.1 mi) to the north. Geese found in Miry and Galloway Bays include the greater white-fronted, snow, and Ross's. Sandhill cranes are also found at the site.[13]
East Lake Diefenbaker (SK055) is located at the eastern end of the lake. It totals 361.69 km2 (139.65 sq mi) and encompasses most of both the Gordon McKenzie and Thomson Arms of the lake. This IBA is designated as critical piping plover habitat.[14]
