Patterson Lake Water Tests 2007
Water sampling was done by the Board of Directors at 10 locations around the lake, to try
to understand a puzzling result from the 2006 Watershed Watch lake survey. That survey showed
the pH of the lake at the deepest spot was alkaline, and became slightly more alkaline during the summer. As we are a
Canadian Shield lake and expected the lake to be slightly acid, we could think of no reasonable answer for the alkalinity nor the increase.
During the course of testing, a number of interesting facts were uncovered. Although we are
a Canadian Shield lake, we are only about 10 km inside the Shield so the land is very
much in transition. As well we have marble bedrock under most of the lake, and marble is
alkaline and disolves over time to make the water alkaline. In 1969 the
Ministry of Natural Resources (MNR) for Ontario commented in notes on a depth level
map of the lake that the lake was slightly alkaline with a pH of 8.3. This pH level was
duplicated in 2007 with a water sample tested at a commerical lab. Comments
from David White who authored Plants of Lanark County, noted the presence of Chara
in the lake and said that this plant liked alkaline water. David’s simplified bedrock
geology map, in the downloaded plant list, also indicated the presence of marble bedrock under a number of local lakes as well.
A check of the Watershed Watch reports from the Mississippi
Valley Conservation confirmed that most of the lakes in our area are slightly alkaline.
So Patterson Lake has been, and still is, slightly alkaline. That
is the way it was. That is the way it is. We just did not know it.
We also know now after a summer of testing that the water in the lake, the input creeks, and
the input springs is very consistent. Water from input springs, input creeks, and the lake itself
at various depths yield similar test results.
We know now that only two of the four creeks running into
the lake flow all through the summer. As well, we have been able to identify and take samples
from a number of lake springs.
Although the prime purpose when the test began was to determine the pH level changes during the summer months using
standard aquarium test kits. Because tests for general hardness (GH), carbonate hardness (KH), nitrites (NO2), and nitrates (NO3) were available on the
test strips, these were included in the results.
We attribute the numerical difference in results from the commercial lab to our test strips
to the accuracy of the test strips and our skill in using them.
The test sites were:
Site 1: 407 Hardwood Ridge Rd
Site 2: Fairs Creek Culvert (outlet creek from the lake)
Site 3: 151 Lakeside Rd
Site 4: Inflow creek near 101 Lakeside Rd until it dried up by August 15.
Site 5: Inflow creek near 221 Lakeside Rd, then when it dried up around June 7,
the artesian well at 151 Lakeside Rd for June 15 to July 15, then a lake bottom spring.
Site 6: 5th Con B near Fairs Creek
Site 7: 632 Fairs Way
Site 8: 293 Porcupine Way
Site 9: Inflow creek near 483 Porcupine Way
Site 10: Inflow creek near 119 Porcupine Way
In the results below:
A pH of 7 is neutral; below 7 is acid, and above 7 is alkaline.
GH (general hardness mg/L) – our results are in normal range;
KH (carbonate hardness mg/L) – our results are in the normal range;
NO2 (nitrite mg/L) – our results are in the very low range which is good; and,
NO3 (nitrate mg/L ) – The interim Canadian Water Quality Guide (CWQG) to protect freshwater
life is 13 milligrams of nitrate per litre of water. This freshwater guideline is
based on a number of scientific studies that examined the impacts of nitrate on animals that live in our lakes and rivers.
22.214.171.124.5 126.96.36.199.4 776.5 188.8.131.52.7 7.57.576.57184.108.40.206 7.57.57 766.566.8 220.127.116.11 766.566.6 7.577 6.56666.6 7 7 7 7.0 7.5 7.5 7.5 7 7.0 7.5 7.5 7.5 7.5 90909088 120130808098 6018030 60120606079 60120806012060606076 18018060 6060606090 606060 6060606060 12012060 6060606076 60 60 120 80 60 60 60 60 60 60 60 60 60 80808082 4080808072 8012040 808010010088 801201204012080808089 120120120 1208012040100 408080 120801204083 120240120 120808040116 80 80 180 113 80 80 80 80 80 80 80 80 80 0000.2 0.50000.2 0.530.5 0.50000.8 310.50.50.50000.7 10.50.5 0.50000.4 0.50.53 0.50000.9 0.50.50.5 0.50000.3 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0002 00002 208020 000021 8020200000016 204020 000013 202080 000025 202020 000014 20 20 0 13 20 20 20 20 20 20 20 20 20
During the summer samples were pumped from the deepest part of the lake location. Water samples were
taken at 5 metres, 10 metres, 15 metres, and the lake bottom (complete with silt). The results were:
Tests done at a commerical lab of the same bottom sample produced a pH of 7.88, and the following results in mg/L:
N02: <0.10, N03: 0.13, Hardness as CaCO3: 110, Calcium: 34, Magnesium: 0
During the summer two samples were taken to a commercial lab for testing. One
sample was from the lake, and one was from the creek (Site 4 above). The pH results
were 8.39 for the creek and 8.26 for the lake. These results in mg/L were:
Creek N02: <0.10, N03: <0.10, Hardness as CaCO3: 102, Calcium: 31, Magnesium: 6
Lake N02: <0.10, N03: <0.10, Hardness as CaCO3: 83, Calcium: 25, Magnesium: 5