Manitoba has an abundant supply of surface water with many large lakes and thousands of smaller ones (chapter 2). However, much of the water is in the north or drains to the north where there is a sparse population. In the south dams and reservoirs have been constructed to conserve water in some areas, whereas in other places projects were designed to drain water from the land to make it suitable for cultivation. The province’s rivers offered enormous potential for hydroelectric power, much of which has now been exploited, starting with a small-scale project on the Little Saskatchewan River and progressing to large projects on the Winnipeg, Saskatchewan and Nelson rivers. Two thermal power stations at Brandon and Selkirk on the Assiniboine and Red rivers illustrate the need for an assurred water supply. Flooding has been a problem since the earliest days of the province, especially along the Assiniboine and Red rivers culminating in the 1997 “Flood of the Century” in the Red RiverValley. Dams, diversions and ring dikes are used to divert the floodwaters to less critical areas.
16.52: The Portage Dam and Diversion
A dam has been built across the AssiniboineRiver above Portage la Prairie to divert water into a floodway at times of high flow, thus reducing the possibility of flooding at Portage la Prairie and Winnipeg. On this large-scale, colour infrared photo, the dam 1, a spillway 2, and the beginning of the floodway 3 can be seen. The dam backs up water necessitating the building of a dike 4 to prevent flooding of nearby agricultural land 5. The blue/green colour of the Assiniboine 6 indicates that it has a high suspended sediment load, and in one location 7 the pink colour indicates that algae are growing in a stagnant area.
Note also the following: 1) meander scrolls are visible south of the river 8 indicating previous river positions and influencing crop growth. Areas of poor growth which are almost white have a linear form 9 corresponding to the shape of the scrolls; 2) deciduous trees are red, have a mottled texture 10, and throw rounded shadows 11; 3) narrow fields east of the river channel 12 reflect the influence of the long lot system of land division used in this area; and 4) the twinned Trans-Canada Highway with service roads on both sides 13 cuts across the northeast corner.