After considering the fact that without the existence of the Portage Diversion, some water would flow into Lake Manitoba near Delta Beach through oxbow lakes and channels which were at one time the original channels of the Assiniboine River when it flowed to Lake Manitoba naturally around 2000 years ago, it is estimated that the Portage Diversion contributed to at least 3 feet of a rise in water levels on Lake Manitoba, accounting for most of the rise of the lake.