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Regaining Control of Water Levels in the South Whiteshell

Posted on: October 4, 2016  |   ,

By Alan Roberts – Chair, WCA Lake Levels Committee
  All cottagers in the South Whiteshell have been sorely affected by the high water levels we’ve
experienced since June 25. Many, many have had major and minor repairs to carry out or pay
for to their docks, decks, and boathouses. Many others have suffered damage 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 two years to
reduce the risk of this from happening, and throughout this summer to try to mitigate the damage.
Some of our suggestions 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 25 rainfall was not a “normal” storm, and may not be repeated in any of our lifetimes.
  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. We have met on numerous occasions with our counterparts in both
Parks and Manitoba Infrastructure and Transportation (MIT) to discuss the most substantive
issues affecting the water levels – and we are finding cooperation on many fronts. We still
have work to do to extract sustainable fiscal budgets for capital works from these two entities,
but the signs of a more reasonable approach are looking promising with the new administration.
  Most cottagers at Falcon Lake will have noticed by now, that “we” (Parks/Sustainable
Development, and 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 study to develop the preliminary design for a 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 and out of the Falcon River. During this time, annual
precipitation levels have increased dramatically – an estimated rise of 60 per cent between 1925
and 2005. Precipitation is projected to increase a further 50 per cent 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 25 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 a 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 travelling 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. The water
flowing over the top of the south Falcon access road from the Falcon Creek and the East Braintree
swamp 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 that 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 is to 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 a 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.
  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 being caught immediately prior to both of the floods of the last three 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 25 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.

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