I have updated the forecast for Lake Manitoba and Lake St. Martin until December, 2007.  The Result is attached in table and graphical format.

Lake Manitoba is presently at 812.0 feet, a good decline from the crest of 812.6 feet in June-July, 2007.

The forecast shows that with normal weather conditions and without any gate adjustments at Fairford Dam, the Lake will decline to 811.69 feet by mid December. The lake level would likely change little during the winter.

Inflows and outflows this year are greater than in 2006 but outflows are somewhat less than in 2005.

Flood Threat Due to Frazil Ice:

During November and December of 2005 we had ice serious frazil ice jams on the Fairford River and the Dauphin River which resulted in closure of PR 513 for an extended period of time due to flooding. Ice jams and flooding also occurred during freeze-up in 2006 but were not as severe as in 2005. Outflows this year are between those of the past two years. Ice jams and flooding are likely to again occur, with the extent to be determined by the nature of the freeze-up. We could reduce the odds of flooding on the Fairford River and the Dauphin River late this autumn by reducing Lake Manitoba outflows at Fairford Dam at this time.

Effect of Reducing Flows at Fairford:

An outflow reduction of 1000 cfs at Fairford Dam would result in conditions similar to those of 2006 when flooding due to ice jamming was manageable with some ice clearing. If we maintain the present gate settings, we could have serious ice jamming unless we have a favourable freeze-up. I have done a calculation to show the effect of a 1000 cfs reduction in outflows on Lake Manitoba levels for the normal weather condition.  It would raise the lake by 0.15 feet by December 10 and a further 0.15 feet for the remainder of the winter, for a total of 0.3 feet. With average precipitation, the lake would be near 812 feet in late March, or 0.5 feet below the top of the operating range. The operating range would not likely be exceeded during the spring if we have average precipitation from now on but could be exceeded if we revert back to above average precipitation from now through the winter and spring. It has been quite dry since mid July, which has allowed the soil to dry, so the odds of above average spring runoff are a little lower than usual at this time.

A reduction in flows at Fairford would be potentially beneficial to Lake St. Martin, which could rise to flood stage this winter after the Dauphin River freezes up if we do not reduce outflows.

The LMRRAC guideline says not to operate the dam as long as Lake Manitoba is within the desirable range of 810.5-812.5 feet. However it appears that the recommendations did not consider downstream effects such as flooding due to frazil ice jams. It may be possible to break ice jams with the amphibex, but there may not be sufficient time since the machine will likely be needed on the Waterhen River at about the same time.

If we plan to reduce flows at Fairford, it should be done very soon, since it takes 6-8 weeks to lower the level of Lake St. Martin sufficiently to have the desired impact on the Dauphin River.