The Portage Diversion system (also known as the Assiniboine River Floodway) was constructed in 1970 to divert the flow of water in the Assiniboine River to an 18-mile diversion channel that empties into Lake Manitoba.
In mid-May of 2011, the diversion channel was opened to help prevent flooding in the Winnipeg urban area. That action eased pressure on downstream dikes. The channel was closed in late May.
Lake Manitoba levels have risen, however, due to the increased flow into the lake, and careful monitoring of water levels and the extent of water spreading downstream, using Landsat satellite data and field measurements, gives response agencies useful information for decision making on controlling stream levels.