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Regaining Control of the Water Levels in the South Whiteshell

Posted on: August 24, 2016  |   ,

All cottagers in the South Whiteshell have been sorely affected by the high water levels we’ve experienced since June 25th. Many, many have had major and minor repairs to carry out or pay for to their docks, decks, and boathouses. Many others to cottage foundations, to “floated” septic tanks, loss of or damage to shoreline, and all cottagers have experienced loss of access to docks, loss of use and enjoyment of water craft, and the list goes on.
At the WCA our lake levels committee has been working tirelessly for the last 2 years to reduce the risk of this from happening, and throughout this summer to try to mitigate the damage. Some of our efforts have fallen on deaf ears, some have been listened to and implemented. The rainfall in June has graphically demonstrated the importance of the issues we’ve been raising, and have given us all lessons that we have hopefully learned from and will not repeat. Having said this, the June 25th rainfall was not a “normal” storm, and may not be repeated in anyone’s life time.
A brief summary of the program we have underway is outlined below. It is a combination of upgrading of physical facilities available for control of the lake levels, and development of management protocols that will reduce the risk of losing control over the levels, and help to protect against flooding reoccurring. We have met on numerous occasions with our counterparts in both Parks and MIT to discuss the most substantive issues affecting the water levels – and we are finding cooperation on many fronts. We still have much work to do to extract sustainable fiscal budgets for capital works from these two, but the signs of a more reasonable approach are looking more promising with the new administration.
Falcon Lake:
Most cottagers at Falcon Lake will have noticed by now, that “we” (Parks / Sustainable Development, and Manitoba Infrastructure and Transportation (MIT)) have lost control over the lake water level. The progressive loss of control has been evident from the lake level records going back more than 25 years, yet no effort has been made to replace or augment the original wooden level control structure (now 58 years old) – in the fall of 2015, MIT initiated a Planning Study to develop the preliminary design for an new water level control facility. In fact half of the original wooden structure was demolished in 2002, and replaced with a steel culvert of similar size, which was then compromised in 2006 by installation of a rock weir to reduce the movement of fish into / out of the Falcon River. During this time, annual precipitation levels have increased dramatically – an estimated rise of 60% between 1925 and 2005. Precipitation is projected to increase a further 50% by 2050 (S. St.George, 2006).
Management protocol used to operate the level control structure was not changed to try to deal with the higher precipitation rate until the fall of 2014 – following the last flood, when we found that the capacity of the Falcon River was exceeded by the heavy rains, and the drainage capacity available couldn’t lower the water level. Again in 2015, after a relatively uneventful summer (in terms of precipitation), we had huge rainfall in mid-November which prevented drawing the lake level down. So again (as in 2014) we came into the summer of 2016 with the water just below flood level. The rainfall of June 25th flooded the entire watershed, and again – consumed what residual capacity was available in the Falcon River, leaving us in a flood that has nowhere to go.
Increasing the capacity of the river is being considered, but the cost of dredging (even if Environment Canada would permit it) would be prohibitive. There is only some 6.5 ft. of drop in elevation from Falcon Lake to Shoal Lake (which it drains into) and this is spread out over some 20 km of meandering river with a bed length more like 50 km long. Beaver dams may be an issue in some areas, but with so little slope on a river traveling through a swamp, no individual dam is going to be much of an impediment. The only predictably viable means of increasing the river’s capacity is to raise its level at the top end – essentially replicating the conditions that a flood creates.
Raising the level can be done artificially by creating a barrier between the lake and the river, and using high volume pumps to lift the water across the barrier. It could be done by turning the south shore access road into a barrier (dam) – except that the biggest part of the problem is the huge attribution rate (inflow into the lake from the surrounding drainage basin) that Falcon Lake and the Falcon River serves. Most of the water that flows out through the Falcon River, comes into the lake as runoff – with a combined flow rate that is just too high to pump feasibly. Recall the water flowing over top of the south Falcon access road from the Falcon Creek and the East Braintree swamp – and it continues to flow into the lake through gated and ungated culverts now. This inflow is believed to be the majority of the extremely high and sustained attribution that Falcon Lake experiences, and floods the Falcon River as well.
Assuming that the Braintree Swamp and Falcon Creek are the main supply channel into the lake, the only obvious solution create a barrier by raising the South Falcon access road right back to the edge of the Town of Falcon Lake, and use the ditch along the west side of the roadway to divert this flow directly into the Falcon River, rather than allowing it to enter the lake. This would reduce the discharge rate needed to control the lake level and reduce the size of whatever control device is developed to “manage” the water level. Numerous hydraulic and environmental issues need to be studied and resolved for this to happen, but it is seen to be prerequisite to the design of whatever type of control facility is selected.
A diversion such as this would at times, cause the Falcon River to be a tributary to the lake. Preventing this from occurring requires the causeway to become a dam, which in turn, prejudices the selection of a pumped discharge level control facility. The WCA has encouraged MIT to make preparations for the diversion of the Braintree Swamp / Falcon Creek drain during the fall of 2016 to conform with MIT’s schedule for the development of a new level control during the fall of 2017.
West Hawk & Caddy Lakes
Both lakes benefit from the ability of West Hawk Lake to buffer large swings in stored water volume with a managed discharge flow rate PROVIDED that the lake water level is MANAGED to maintain available storage capacity within the normal operating range. “We” have learned this lesson from having been caught immediately prior to both of the floods of the last 3 years, having too much water in the reservoir, and having our ability to provide this buffering function compromised. Greater diligence in maintaining this buffer (operating the lake level) has been offered by MIT. It should be noted that the rainfall on June 25th of this year, exceeded the normal buffering capacity available, however the severity of the flooding would have been lessened had more attention been paid to achieving the necessarily low drawdown level during the previous fall.
The biggest factor affecting the severity of the flooding on Caddy Lake, was the hydraulic limitations of the tunnels beneath both CN and CP Rail lines north of Caddy. These constraints are outside the purview of the Manitoba Government however, both CN and CP Rail are being approached by the WCA with a plea to increase the capacity of these crossings of the Whiteshell River. Relief from these constraints will be expensive, and yield no return to either Rail line. Though we don’t anticipate immediate success, we are hopeful that their cooperation will be forthcoming within the “near” future.
By: Alan Roberts
Chair – WCA’s Lake Levels Committee

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