Water Clarity
We have been taking Secchi Disc readings for many years now as part of the Ministry of Environment's Lake Partner Program. Between 1997 and 2001 we had fairly constant readings from 2.1 3.1 meters at the west end of the lake which was the only part officially tested. In the past eight years we have had up to six volunteers and have been able to cover a greater area of Manitouwabing Lake including Robinson Lake. The readings have been in the range of 1.4 3.1 m. Based on Secchi Disc readings our lake would be classified eutrophic (enriched with higher levels of nutrients), but this is mostly due to the tea colour caused by the higher tannin content of our lake which results from organic matter being washed into the lake from swamps, tree foliage and run off from construction sites and excessively cleared shoreline.
The Association's volunteers are continuing to take Secchi Disc readings from May to September. Readings vary somewhat throughout the summer, but are stable overall and average about two metres.
Samples taken of from six to12 locations (depending on the number of volunteers), including Robinson Lake, since 1998 has shown on average 12g/L, which classified the lake as "Mesotrophic" (moderately enriched with some nutrients).
Over the years we had a few "spikes" in the Jones Bay/Longhorn area [37g/L] and in the McKellar Bay area [47g/L]. It is suspected that a reason for this could be that in shallower bays there is more decay under the ice in the winter, which uses more Oxygen and this releases the phosphorus from the sediment.
There appears to be a slight trend that phosphorus levels are increasing in Lake Manitouwabing. We can control the build-up by reducing the importation of phosphorus into our lake. How? By reducing excessive tree clearing near the shore and not having a lawn right to the lake, by avoiding the use of fertilizer, preventing surface runoff from your property into the lake, repairing faulty septic beds, regularly inspecting and pumping septic tanks [every three to five years depending on usage], using low Phosphorus cleaning material, reduce the use of dish washers and laundry washing machines and protecting your septic system from too much water.
Lakes with levels over 20g/L are classified "Eutrophic" (highly enriched). At phosphorus levels of over 15 to 20 g/L, the algae levels rise and build up on boat hulls and shoreline, water starts to taste and smell bad, weed problems increase, there is more summer and winter fish kill and the general water quality decreases.
A planning consultant stated at a FOCA meeting: "Municipalities have little or no scientific knowledge and their only interest is increasing the tax base until it is too late." The Lake Plan should be part of the Official Plan for a Municipality in order to control water quality, percentage natural shoreline, boating h.p., etc. It would be beneficial if members in the high result areas could become more vigilant and determine possible causes for the high Phosphorus levels.
