Because of a one-in-a-1000-year rain event that flooded Lake Wahtopanah at Rivers, Man. engineers are going to thoroughly examine Rivers dam to see if the structure is still worthy to withstand future high flows.
There was a point, at the end of June, when residents downstream of Rivers dam on the Little Saskatchewan River were packing up their dogs, cats and personal valuables and getting out of the valley upon the advice of Manitoba Infrastructure.
After some 10 inches of rain in two days, Lake Wahtopanah was at an all-time high and the flow over the dam spillway was carrying twice the volume of the flood of the century in 2011. Running at 12,000 cubic feet/second (5,000 cfs in 2011) Manitoba Infrastructure, under the advice of government and private engineering firms lost confidence that the dam would hold.
Now, at the start of September, two months later, the water level of the dam is at the crest of the spillway and the spillway has stopped flowing.
Manitoba Infrastructure is advising that the water flowing through the conduit below the dam is at about 175 cfs.
A thick film of algae has prevented a detailed inspection of the spillway including the concrete walls, slabs and joints and that must be scrubbed off. As soon as the clean-up is done the Province will look into the health of the structure this fall.