Lake Wahtopanah, also known as Rivers Reservoir, is a lake on the Little Saskatchewan River just west of the Town of Rivers within the Riverdale Municipality. Its dam was built by the Prairie Farm Rehabilitation Administration in 1960 to supplement water supplies for irrigation. It also provides the water supply for the Town of Rivers, stock watering and recreation. Recreational activities to do at the lake include: summer fishing, ice fishing, snowmobiling (winter), boating, skiing, wakeboarding, kayaking, canoeing, paddle boarding, and swimming.

The lake is approximately 2,000 feet (610 meters) wide, and six miles (10kms) long. The deepest point is about 50 feet (15 meters). The reservoir stores approximately 24,500 acre feet and covers an area of 1,580 acres. The drainage area is 1,260 square miles and extends well into Riding Mountain National Park.

Lake Wahtopanah is home to the Rivers Provincial Park which is located on the west side of the lake. For more information on the Provincial Park, click here. On the east side of Lake Wahtopanah you will find Daly Beach and Jake Fast Park. These locations are home to campers, cabin-owners, and year-round residents. Docking stations can be found on either side of the lake.