Lower Beverley Lake Water Quality
Test Results Through 1999
Water Clarity
Measurements are made with a Secchi disc to determine the depth
of effective light penetration into the lake. The region from
the water surface to the lower depth of effective light penetration
(twice the Secchi disc reading) is where there is just sufficient
light to sustain photosynthesis and allow aquatic plants and algae
to grow. The greater this depth, the clearer the water.
If the Secchi disc reading is less than 3 meters, the lake is
considered "enriched" (too many nutrients).
Clarity Sampling was expanded in 1994 to include Kendricks Bay
and the area above Whiskey or Black Jack Islands, in addition
to Oak Bay (the area beyond the narrows by Morton Creek). In 1998,
measurements were initiated at the Upper Lake outlet/dam, to monitor
input to Lower Beverley Lake.
Data available back to 1971 indicates Lower Beverley Lake measurements
(displayed in the Water Quality exhibit) have been less than 3
meters, but had been demonstrating an improving trend since 1990.
Results deteriorated in1998, due in part to unusually high water
levels in early July which resulted in increased watershed runoff.
Clarity improved in 1999 consistent with a regional trend attributed
to low rainfall/nutrients staying on land and wetlands.
Algae Level
Water clarity is an indirect measure of the algal density in
the lake, which is affected by the level of nutrients present.
Water samples are chemically analyzed to determine the nutrient
level (the lower the level, the better). Chlorophyll concentration
measurements (an indicator of the amount of microscopic algae
in the water) were used through 1995; 4 or more micrograms/Liter
indicates high algal density and is considered "enriched"
(too many nutrients). Lower Beverley Lake measurements were above
this level through 1995.
In 1996, the Ministry changed the analysis to the phosphorus
concentration (the single most important nutrient governing the
level of algae in the water), and in 1997 decreased the number
of samples in each lake. On phosphorus measurements, we improved
and fell into the "moderately enriched" (some
nutrients) category, until our improving trend reversed in 1998.
In 1999, nutrient levels fell in many Ontario lakes, and early
measurements in Kendricks Bay matched this trend, although later
measurements were above the "enriched" threshold.
Weekly Clarity Profile
The annual Secchi disc data (plotted in the Water Quality exhibit)
represent the arithmetic average of weekly samples each summer.
It is interesting to see the change in water clarity as the lake
progresses through its seasonal cycle. In 1998, we recorded best
ever measurements in Kendricks Bay and Whiskey Island late in
June, before deteriorating in July reflecting the high water runoff
and the period in which aquatic plants mature. In 1999, results
were much more consistent, and more favorable over the full summer
measurement period. Both years are displayed in the Weekly Profile
chart.
Zebra Mussels
In 1998, we were able to expand our testing program to include
participation in the Federation of Ontario Cottagers’ Association
(FOCA) Zebra Mussel Monitoring Program. The analyses indicate
the presence of the first stage of Zebra Mussel activity in 4
of 5 areas sampled in Lower Beverley Lake (Kendricks Bay, mouth
of Mill/Delta Creek, Marble Island/Dawson Bay, and Oak Bay). No
new Zebra Mussel invasion was found at other lakes joining the
FOCA program in 1999, but an outbreak of Spiny Water Fleas in
two previously uninfected lakes has occurred.
The first stage (veliger) is a juvenile stage of the mussels’
life cycle, and is the only stage characterized by free swimming
activity. Veligers are microscopic and this stage allows wide
dispersion and settlement of Zebra Mussels over wide ranges until
settling in a suitable habitat occurs, and the growth and feeding
necessary to reach the adult reproductive stage begins. At this
point, they are sand grained-size larvae and attach to any hard
surface (docks, boat hulls, water inlets, motors, etc.).
Water Testing Overview
LBLA has been expanding water testing since 1994 to better evaluate
water quality trends and potential problem areas. As governmental
funding has been cut, we have aggressively sought alternative
sources for testing, and are making up the shortfall to ensure
continuing stewardship of the lake. Our current testing includes
clarity and phosphorous measurements at Oak Bay (unsettled area/infrequent
input from the Rideau chain), Kendricks Bay (LBL deep basin),
Black Jack Island (input from Coolican Creek), and Upper Lake
dam (inlet).
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