Lake of the Prairies

The Shellmouth Reservoir is a man-made reservoir on the Assiniboine River in Manitoba and Saskatchewan, Canada. The Shellmouth Dam () is an embankment dam built by the Prairie Farm Rehabilitation Administration (PFRA). Construction started in 1964 and was completed in 1972 costing CDN $10.8 million. The dam is high and long. The reservoir is in length and stores 390,000 acre feet (480 million cubic metres) at the spillway crest level of . Outflows are controlled by a gated conduit and a wide concrete chute spillway. The normal summer level target is between and . The dam and reservoir are part of a strategy to reduce the risk of flooding on the Assiniboine River and in Winnipeg. For example, in the 1997 Red River Flood, the inflow to the reservoir peaked at while the outflow never exceeded . The reservoir is also used to supplement flows on the Assiniboine when conditions are dry ensuring water supply for Brandon, Portage la Prairie, irrigators and some industries. The reservoir is also known by the name "Lake of the Prairies". Asessippi Provincial Park is established around the southern arm of the lake.