Weed Management & Water Quality Improvement Strategies
Chemical Treatment
Chemical treatment is the most common and widely
used strategy for weed management in inland lakes. The benefits of chemical treatment, when properly implemented, is immediate
relief from problem species including Eurasian Water Milfoil and algea. The current chemical treatment program for Sherman Lake
has been moderately to highly effective in controlling milfoil and algea. Unfortunately, chemical treatment does nothing to
address the root cause of excess nutrients in the lake. This is why we have seen a rapid increase in the growth and spread of native pond weed, water meal and lily pads.
Mechanical Harvesting
Harvesting involves the physical removal of weeds from
the lake using Heavy Duty Harvesters. Harvesting has the advantage of removing some organic material and, therefore, nutrients
out of the lake. Harvesting can be expensive. It is not uncommon for lakes the size of Sherman Lake to spend between $25,000 and $40,000
per year on harvesting programs.
Watershed Management and Non-Point Source Control
Watershed Management is a MUST DO strategy
for any Lake Management Program that is interested in long-term results. Watershed Management and Non-Point Source Control involves
the careful evaluation and control of nutrient sources flowing into the lake. Solutions range from implementing the central sewer
strategy to having all residents eliminate the use of lawn and garden fertilizers containing phosphorous - the key ingredient for
accelerated lake weed growth.
Watershed Management is a long-term strategy for improving the health of Sherman Lake. Used
in conjunction with other strategies it will pay dividends and save significant money by reducing the need for harvesting, chemicals
etc. To learn more about what you can do to support this strategy click here.
Dredging
Dredging has been used for decades
as an "option of last resort". Dredging has the advantage of actually addressing the root cause of internal nutrient loading
by physically removing nutrient laden organic material and sediments from the lake bed. Unfortunately, dredging is prohibitively
expensive and difficult to obtain permit approval from the Michigan DEQ. Based on researching dredging projects for other lakes,
a dredging program for Sherman Lake would most likely exceed $1million dollars spread over several years.
Aeration
There is evidence
that aeration combined with the use of specialized organic compounds can have a significant beneficial impact on reducing the nutrient
load in the lake. Aeration strategies are designed to restore and accelerate the lake's natural ability to "clean itself" of
nutrients like nitrogen and phosphorous. This strategy reduces weed and algea growth by limiting the available food supply the
weeds and algea need to grow. There is also evidence that Aeration can reduce and reverse the accumulation of the "muck" on the lake
bottom.
Implementing an aeration strategy on Sherman Lake would require a long-term commitment. Aeration is not cheap,
but it is significantly less expensive than dredging. Academic opinion on aeration is mixed. Careful study of aeration as
a strategy for Sherman Lake is warranted. There are several approaches and philosophies on aeration methods.
For a comprhensive review of the concept and theory behind whole lake aeration visit www.clean-flo.com.
Biological Controls
Eagle
Lake in Paw Paw, Michigan has seen a reduction in milfoil growth using the milfoil weevil. The weevils are a species of insect
native to North American that have a hearty appetite for milfoil. The weevils are harmless and nearly invisible to the human
eye. In sufficient numbers the weevils can keep milfoil in check without the use of chemicals. It is possible that Sherman
Lake already has a population of these weevils active in the lake.
Implementing this strategy would involve the introduction
of many additional thousands of weevils into the lake and careful management of their ability to take hold and thrive in the lake
and on the surrounding shoreline. To learn more about this fascinating bug visit: http://fwcb.cfans.umn.edu/research/milfoil/milfoilbc.html. We
will be investigating this approach and other biological control methods carefully over the coming months. For more information on
other biological control measures visit: http://plants.ifas.ufl.edu/guide/biocons.html
Lake Drawdown
Lake drawdown strategies
are often used to help mother nature kill the weeds in the winter and make it harder for them to re-establish the following spring.
Lake drawdown involves lowering the lake level by several feet so that the ice and freezing action can damage the root systems of
the aquatic weeds and limit their regrowth the following year. Unforturnately, because Sherman Lake is a closed basin lake
there is not a practical way to get the water out and back in, therefore, this strategy is most likely not a viable option for
us.
Hypolimnetic Withdrawl
Hypolimnetic withdrawl essentially involves the siphoning off of water and, if possible, muck from
the bottom of the lake. The intent is to remove the nutrient rich water and muck from the lake in a way that is less invasive
and costly than dredging. This approach has, at best, shown mixed results. One significant barrier to implementing this strategy
is the disposal of the water and muck that is removed from the lake. Obtaining DEQ permit approval for this strategy is
a significant impediment.
Summary and Conclusions
Achieving results will require the application of a variety of strategies over
the next several years. The focus for 2007 will be to maximize the impact of our management efforts within the confines
of the current funding program. In addition, we will work to raise additional funds to implement a more comprehensive Water
Quality Monitoring Program and test and evaluate more comprehensive strategies for implementation beginning in 2008.
Please
take the time to review what you can do now to improve the health of the Lake and to understand the funding implications of
implementing a more comprehensive program beginning in 2008. For a more comprehensive review of weed management and water quality
improvement strategies, please visit our Lake Strategies Work Space which we are using to contiuously compile information
and evaluate the potential of all available improvement strategies.
