Lake Steward’s Report By Mike Thorne
Hi fellow cottagers, this is my first attempt at explaining the water quality in our lake based on some recent sampling. On August 20, 2017 Don Drouillard and I completed the annual lake sampling which consists of sampling for E. coli-an indicator of bacterial pollution from warm blooded folks like us, Total Phosphorus which is an indicator of potential algae blooms and pH which is an indicator of loss of alkalinity in the lake at five sites around the lake. We have been sampling at these same 5 sites for a number of years now which gives us a good snapshot of Water Quality in the lake over time. We also take Secchi disc readings at each location which gives us an indication of whether water clarity in the lake is deteriorating or improving over time.
Samples are taken at roughly the same location each year at 1. Inlet 2. Gull Rock 3. Deep Bay 4. Miners’ Bay and 5. Lake outlet. A 6th location is sampled off Rackety for Total Phosphorus as part of the Lake Partners Program-no results yet.
It was a calm day that had been preceded in days previous by heavy rainfall and strong winds. Overall, the following results were representative of previous years, with no indication that we are undergoing any negative trends in Lake Water Quality.
All areas sampled on the lake were within safe swimming levels of 20 cfu /100 ml. Considering the amount of rain we had this summer the E. coli levels were low being 2 cfu/100ml or less except for the inlet to the lake and opposite Rackety which were 12 and 6 cfu/ 100ml respectively which is to be expected as the water moves from the inlet to the outlet.
The Total Phosphorus levels were consistent with other years ranging from a high of 9.5 ug/l (or parts per billion) at the inlet to 4.9 ug/l at the outlet. These levels are below what is considered problematic for algae to become prolific due to excess phosphorus in the water. If a lake has levels below 15 ug/l it is in good shape. However some lakes have experienced algae blooms at below 15 ug/l so we will keep a close watch on trends in the future. Our sampling results indicated phosphorus levels between 9.5 ug/l at the inlet to 4.9 at the outlet. As expected the water at the mouth of the lake has higher readings which diminish as the water flows south to the outlet due to dilution. Also we noted much more algae growth at the inlet area likely due to the higher concentrations of phosphorus.
pH readings give us an indication of the amount of alkalinity or buffer we have to combat things like acid rain. Ontario Provincial Water Quality Objectives for surface water indicates that lakes with pH readings between 6.8 and 8.5 is acceptable. However it is desirable to be on the basic side with pH between 7.1 and 8.0. Recent samples had our pH ranging from 7.3 to 7.6 which is good and consistent with past results.
Secchi disc readings give us an indication of the clarity of the water and readings less than 4.0m is an indication of excess turbidity (cloudiness) in the water which can be a result of excess algae in the water. A certain amount of algae is healthy because among other things that is what fish etc. eat to survive and grow. Our sampling results indicated Secchi disc readings between 3.1m at the inlet to 4.0m off Rackety 4.7m at Gull Rock and 5.1-5.5m in the rest of the lake. The low reading at the inlet is partially due to the amount of rainfall we have received and the higher than normal water flows in Gull River which increases the amount of sediment in suspension at the inlet. Overall the secchi disc readings indicate we have good water clarity in our lake.