|Primary inflows||Earthen aqueduct from Lake Diefenbaker|
|Max. length||14.4 km (8.9 mi)|
|Max. width||0.8–1.2 km (0.50–0.75 mi)|
|Surface area||1,200 hectares (3,000 acres)|
|Average depth||5.15 m (16.9 ft)|
|Max. depth||9.39 m (30.8 ft)|
|Water volume||61.5×106 m3 (49,900 acre·ft)|
Blackstrap Lake is a man-made lake in central Saskatchewan, Canada, south of Saskatoon in the rural municipality of Dundurn No. 314. The lake was created as a reservoir in 1967 as part of the Saskatoon South East Water Supply System. Blackstrap Lake has an area of 1,200 hectares (3,000 acres) (14.4 km x 0.8-1.2 km at a depth of 5.14 m) and is used to support irrigation, industrial and municipal water supply.
The Blackstrap valley is an ancient spillway created by the melting of the Wisconsin glacier. Two formerly small and marshy lakes, Theresa Lake and Blackstrap Lake, were in the area now covered by the reservoir. First Nations peoples used the valley for hunting and shelter. European settlers farmed the flat land of the valley during dry seasons, some of which forms the present lake bed. The steep drought during the Dirty Thirties prompted the construction of Gardiner Dam across the South Saskatchewan River. A series of gravity-fed canals and reservoirs was also built to supply water to the areas southeast of Saskatoon, with Blackstrap being the largest reservoir. The north and south Blackstrap dams were constructed in 1967 and are operated by the Saskatchewan Water Security Agency. The dam stores water to supply the villages of Thode and Shields, the PCS Allan potash mine (via the Bradwell Reservoir) and the Mosaic Colonsay potash mine (via Zelma Reservoir). A channel connects the south end Blackstrap Lake to neighbouring Indi Lake.
Blackstrap Lake is a major part of Blackstrap Provincial Park. A recreation area was established soon after the completion of the lake, and further developed with a ski hill for the 1971 Canada Winter Games. The provincial park was established in 1986.
- "Blackstrap History". Saskatchewan Parks. Retrieved 2013-11-15.
- C. P. Hwang; P. M. Huang & T. H. Lackie (May 1975). "Phosphorus distribution on Blackstrap lake sediments". Journal. Water Pollution Control Federation. 47 (5): 1081–1085. JSTOR 25038706.
- "Non-Potable Water Supply Systems". SaskWater. Retrieved 2013-11-15.
- "Blackstrap Coulee". Important Bird Area Program. Bird Studies Canada. Retrieved 2013-11-15.
- "Dams and Reservoirs". Saskatchewan Water Security Agency. Retrieved 2013-11-15.
- "Background Report - South Saskatchewan River Watershed" (PDF). Saskatchewan Watershed Authority. September 2007. p. 61. Retrieved 2013-11-15.