Looking North towards the creek

Background
     Water in Otter Lake is supplied from an extensive drainage area (10,000 acres or more) via numerous parent streams, yet the lake has only a single outlet, Otter Creek. Since the 1960's beavers have been quite active in the upper reaches of the creek. Beaver dams are one of several factors contributing to the level of water in the lake. As a result, beaver activity in the creek combined with the early spring runoff can often have a significant effect on the water level in the lake. Very high water levels have been experienced in the early spring, especially if there has been a rapid spring thaw. These high water levels have caused local flooding to private access roads and low lying properties which is obviously a serious concern to some property owners. After the spring runoff is complete the lake level usually drops significantly over the course of a normal summer, with most of the water loss resulting from evaporation. Water levels can again rise in the fall, when beavers again become active in the creek, however following the freeze over the lake level will drop during the winter months

Control of Water Levels
      In 2000, an attempt was made to control the water flow in the creek by the installation of "beaver bafflers" in the beaver dams. A "beaver baffler" is essentially a tube inserted through the base of the beaver dam. OLLA supported and was involved in beaver baffler installation. Overall, the bafflers were not successful primarily because they required continual maintenance. OLLA therefore adopted a policy of non interference with water flow. The current OLLA policy on water levels that was proposed and ratified by the membership in 2006 is that "the natural flow of water into and out of Otter Lake should be left to the forces of nature. In the event that water level extremes (high or low) occur, OLLA will use its best efforts to communicate with authorities that can undertake remedial action on water flow, either inflow or outflow, to reduce damage, pollution, and other environmental effects. This policy will be construed and applied in accordance with the laws of the Province of Ontario and of Canada".

Water level monitoring
      OLLA continually monitors water levels. Water depth is measured several times a month at the culvert on Otter Lake Road. The graph below shows water depth in the culvert in feet and meters above sea level from September 2003 (when recording began) to the present and clearly indicates that the water levels can fluctuate quite dramatically. In the fall of 2003 and in the spring of 2005 the water level was quite high, however the lake level dropped a total of 2 feet between April and September of 2005. The summer of 2005 was incredibly hot and dry with virtually no rain in June, July and August. Hence, there was considerable water loss by evaporation. In addition beaver dams in the upper reaches of the creek were destroyed and beavers were removed from the creek. Thus, there was increased outflow of water from the lake that was not replenished. It should be noted that this activity in Otter Creek was NOT initiated NOR supported by OLLA, however since the Association does not have policing powers, there is little that can be done if individuals, whether they be Otter Lake property owners or from elsewhere, choose to take it upon themselves to trespass on private property for the purpose of removing dams and/or beavers.
      At the AGM, held on July 28th, 2007 the OLLA Board of Directors proposed that a water level of 34 inches below the top of the culvert at Otter Lake Road (a depth of 2.83ft) might be a level that is acceptable to all property owners and visible markers indicating the level were placed on prominent landmarks around the lake. The reference line in cyan on the graph below shows when the lake has been above or below this 34 inch level. This level was reached early in August, 2007, and again in August 2008. In 2009 the level was reached much earlier, in May and has been at least 6 inches or more below that level until the lake level started to rise in the Fall. The 34 inch level was reached again in December prior to freeze over.

Water Level Management by RVCA
      In June 2007, in response to concerns/complaints received from property owners regarding flooding of property and access roads, the Rideau Valley Conservation Authority (RVCA) proposed the following action.
      "In an effort to balance the aquatic ecosystem needs and landowner flooding issues it is recommended that Dam #1 and #2 be breeched in the center of the dam.  The following mitigation measures should be implemented during beaver dam removal activities.

  • Breeching of the beaver dam should be carried out in a manner that minimizes downstream sediment load.
  • Breeching of the beaver dam should occur during low flow conditions and on days when rain is not expected.
  • Only a small portion of the dam should be pulled back at one time to allow the water from the beaver pond to be released slowly.  As water levels decrease, the size of the opening may be increased to allow complete drainage of the retention area.
  • Work is to be completed by hand with NO heavy equipment on the bed of Otter Creek at any time.
  • Areas downstream of the beaver dam should be monitored during breaching activities to determine whether damage to the channel and adjacent properties receiving additional water volumes are occurring.
  • Fish that become trapped in isolated pools as a result of beaver pond de-watering should be relocated to the main channel of the watercourse.

      Dam building nuisance beaver for Dam #1 and #2 should be trapped using appropriate trapping methods".
     This work was completed and as a result RVCA reported that by June 12, 2007 the lake level had dropped 3.5 inches. Unfortunately the heavy rains in July and the probable return of beavers to the creek essentially nullified this drop in water levels. As a result RVCA was forced to again breech beaver dams and trap beavers in the creek. This was done early in August. Be aware that these actions to lower lake levels were an RVCA initiative. OLLA did NOT make any requests to RVCA regarding water levels.
     Note that since there was very little rainfall in August and because RVCA again breeched beaver dams and trapped beavers, the lake dropped below the 34 inch level but did not drop much further despite the continued lack of rainfall in September and October.

Current Water Level Situation
     The graph on the right shows the lake levels from January 2008 to the present.The alarmingly high water levels in January 2008 resulted from the heavy snowfalls we experienced in December, virtually all of which melted in early January when temperatures rose well above freezing for many days. Fortunately, Otter Creek remained open and flowed well all winter and the lake level dropped significantly. However, as the incredible amounts of snow we received in February and March started to melt, the lake level rose rapidly and peaked around mid April. At that time, the water depth at the culvert on Otter Lake road was measured at 4ft which is the highest level recorded since records have been kept. Therefore, owners of low-lying property would have experienced significant flooding. In addition some private access roads (particularly road O9) would have flooded. Water levels dropped considerably in May (almost by 1ft) but rose again in June due to the heavy rainfall we received. This prompted RVCA to take action as a result of further concerns/complaints received from property owners. The action taken was to once again perform a partial breach of beaver dam #1 in Otter Creek and trap the beavers. The June water level values indicate that the lake level has in fact risen slightly despite RVCA's actions. However, all property owners should be aware that according to Environment Canada there were only 8 days in June 2008 without rain. Also, the Federation of Ontario Cottages’ Associations (FOCA) has been informed that there were high water levels in the Muskoka, Kawartha, Trent/Severn regions as well as Rideau Lakes. Thus, we will all have to accept that Nature is the primary determining factor of water levels and there is not a great deal that we as mere mortals can do to change things!
     Nonetheless, given the minimal rainfall we had in August and September the lake level dropped considerably and was at its lowest level for 2008 in October. With the increased rainfall and the snow we received in November and December (most of which melted during the mild weather after Christmas), the water level rose significantly, but was still considerably lower than it was at this same time in 2007. This past winter, the lake had frozen completely by Christmas Day, somewhat earlier than usual but Otter lake was still the last lake in the area to freeze. With the mild weather we had in April the ice was off the lake by Easter. Given that there was not a heavy snow pack last winter and not a lot of heavy rain, the spring water levels were lower than they were at this time in 2008 and would not have resulted in any significant flooding of low lying properties and/or access roads
     As reported at the AGM in July RVCA has not performed any beaver management in the upper reaches of Otter Creek in the Spring of 2009, and it would appear that beavers did not return to the Creek. As a result, even though according to Environment Canada we received 130mm of rain in July the lake level remained about the same as it was in June and there was excellent flow in the Creek. However, even though August was considerably hotter and dryer than July, the level remained constant. This may indicate that beavers have once again returned to the creek! Nevertheless, water levels remain considerably lower than they were at this time last year. September continued to be fairly dry and the lake level dropped about 3 inches so that the level was about the same as it was this time last year. Since we had a fair amount of rain in October and November the lake level has risen significantly. There was also minimal flow in Otter Creek at the Otter Lake Road culvert again suggesting that beavers may once again be active in the upper reaches of Otter Creek. The fact that water levels increased significantly in November and December indicates that this was indeed the case. RVCA did perform some beaver management during this time period. Several beaver were removed by the trapper and the creek has been kept open. Therefore even though the water level in December, January and February has been about as high as it was in May, 2009 there is good water flow in the creek. All property owners should be aware that RVCA's beaver management program came to an end in December 2009. The lake finally froze over completely in late January, however Otter Creek still remains open at the Otter Lake road culvert.

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Last update June 2009