2023 WATER QUALITY RESULTS (Click here for full report)
Charleston Lake Association has been sampling water for over 20 years. Again in 2023 summer, forty-
two phosphorus samples and water clarity recordings were collected over the period May 23rd to
October 23rd inclusive; six samplings from each of seven basins in the lake.

The 2023 total phosphorus from the MOECP Lake Partner Program showed a mean average of 9.14 ug/L
compared to the average of the previous 5 test periods (2017-2022) of 9.07 ug/L. These levels are
below (better) than the Provincial Water Quality Objective of 10 ug/L, and have been for over 10 years.
The period of 2000-2004 had a whole lake mean value of 14.027 ug/L, so the last 10 years have shown a
remarkable improvement. A big part of the initial improvement was the result of the zebra mussel
colonization of the lake, but that appears to have been stable and/or declining for a number of years
and the results continue to be stable. The mean values (2023) for the various basins are 8.24 Donaldson
Bay, 8.91 Goose Island, 8.93 Eastern Water, 8.95 Webster Bay, 9.14 Big Water, 9.71 Deep Water
(Runnings Bay), 10.11 Southern Water

Charleston Lake has reached a steady-state equilibrium with respect to total phosphorus concentration
for the period 2009- 2023 inclusive that clearly places Charleston Lake in the oligotrophic category for
this parameter.

During the spring, summer and fall of 2023, Charleston Lake once again experienced excellent water
clarity (Average Secchi depth 8.30m); this value is higher than the last 5 year average of 6.66m and
closer to the 2009-2013 period when the zebra mussel colonization was at its peak. When compared to
the first five years (2000 to 2004 inclusive) of clarity data the improvement is remarkable. The mean
water clarity value for the first five years is 4.30m. The largest part of the improvement in clarity is the
result of the zebra mussel colonization of the lake, but that appears to have been stable for a number of
years and the results continue to improve. Donaldson Bay had the highest average clarity at 9.32m,
ranging to Southern Waters at 7.15m average

Water clarity has improved so much in recent years that the mean value for the 22-year period of record
(6.252 m) places Charleston Lake in the oligotrophic category for the entire time frame, despite the fact
that for the first five years of that period (2000 to 2004 inclusive) the water clarity averaged only 4.305
m. Oligotrophic lakes have a water clarity & quality; 5.0 meters.

The average calcium concentration from 14 samples this year was 25.70 mg/L, virtually unchanged from
the last 40 years. For high alkalinity hard water lakes like Charleston it should not be anticipated that
this will decline over time.

The average chloride concentrations from the 14 samples was 8.48mg/L, ranging from 8.65 in Big Water
to 7.42 in Southern Waters. This is virtually unchanged for last 40 years and is in line with
uncontaminated lakes.

Through a combination of good luck and good management we have seen Charleston Lake return to
near pristine conditions from where it was a generation ago.  We can't take it for granted but we can
enjoy the result and do what we can to make sure it further improves.
John Willson and Gary Nielsen