[4] Rafferty Dam (49°09′08″N 103°05′22″W / 49.1522°N 103.0894°W / 49.1522; -103.0894) is at the south-eastern corner of the lake, about 4.8 kilometres (3.0 mi) upstream from Estevan.

The dam and reservoir provide flood control along the Souris River, irrigation, and recreation.

The park includes a golf course, a campground, cabins, Pederson Place (a 5,000 sq ft (460 m2) multi-purpose hall with a 3,000 sq ft (280 m2) deck), a beach area, group camping, a boat launch, hiking trails, and four residential cottage subdivisions.

With the building of the Rafferty Dam and subsequent flooding of the valley, the park was moved to its current location.

It was named after Dr. William Graham Mainprize, who served the nearby community of Midale for over 50 years.

[10][11] Fish commonly found in McDonald Lake include walleye, northern pike, white sucker, and yellow perch.