feasibility study reducing/removing eurasian watermilfoil

Transcription

FEASIBILITY STUDY
REDUCING/REMOVING EURASIAN WATERMILFOIL
LAC ST-PIERRE, VAL-DES-MONTS, QC
LAKE ST-PIERRE, VAL-DES-MONTS, QC
Prepared for the Lac St-Pierre Association
August 2014
By Mélanie Renaud, Ecology Consultant
TABLE OF CONTENTS
Table of contents
Introduction ______________________________________________________________________________________________ 1
Lac St-Pierre Overview___________________________________________________________________________________ 2
The watershed _____________________________________________________________________________________________________ 2
Topography_________________________________________________________________________________________________________ 2
General physical characteristics __________________________________________________________________________________ 2
List of uses _________________________________________________________________________________________________________ 6
Water quality ______________________________________________________________________________________________________ 13
Parameters ________________________________________________________________________________________________________ 13
Diagnosis and identification of the causes of the Eurasian watermilfoil invasion problem ______ 31
Aquatic plants _____________________________________________________________________________________________________ 31
Invasive aquatic plants ___________________________________________________________________________________________ 32
Control Methods _______________________________________________________________________________________ 36
Comparison of proposed systems _______________________________________________________________________________ 36
Canadianpond.ca system _________________________________________________________________________________________ 36
Lake Savers and Weeds B’ Gone systems________________________________________________________________________ 39
Hypolimnetic aeration using oxygen ____________________________________________________________________________ 42
Bioaugmentation _________________________________________________________________________________________________ 42
Mechanical cutting or harvesting ________________________________________________________________________________ 43
Comparison of methods __________________________________________________________________________________________ 44
Costs _______________________________________________________________________________________________________________ 44
Feasibility of proposed control systems ______________________________________________________________ 46
Expected efficiency and success _________________________________________________________________________________ 46
Similar situations _________________________________________________________________________________________________ 46
Lac St-Pierre and hypolimnetic aeration ________________________________________________________________________ 48
Bioaugmentation _________________________________________________________________________________________________ 49
Harvesting _________________________________________________________________________________________________________ 49
Environmental impacts ________________________________________________________________________________ 51
Human and socioeconomic environment _______________________________________________________________________ 51
TABLE OF CONTENTS
Natural environment _____________________________________________________________________________________________ 51
Other recommendations _______________________________________________________________________________ 53
Holistic approach and Lac St-Pierre Association efforts _______________________________________________________ 53
Municipality of Val-des-Monts ___________________________________________________________________________________ 53
Water quality analysis ____________________________________________________________________________________________ 53
Lac McMullin ______________________________________________________________________________________________________ 53
Required approvals_____________________________________________________________________________________ 55
The Department of Sustainable Development, Environment and the Fight against Climate Change _______ 55
Available resources _____________________________________________________________________________________ 56
Partnerships and financial resources ___________________________________________________________________________ 56
Conclusion ______________________________________________________________________________________________ 57
References and bibliography __________________________________________________________________________ 58
Contact information ____________________________________________________________________________________ 59
Appendices _____________________________________________________________________________________________ 60
INTRODUCTION
Introduction
Lac St-Pierre is located within the MRC des Collines in the municipality of Val-des-Monts, north of the cities of
Gatineau and Ottawa. The municipality of Val-des-Monts is a region appreciated for its lakeside tourist
attractions. There are more than 120 lakes in this municipality alone. Lac St-Pierre and Lac McGregor are the only
two lakes with a public boat launching ramp in the municipality. Because of this, Lac St-Pierre features many
tourist activities such as water sports, fishing, and swimming. The lake is also home to a water ski school.
The presence of the Eurasian watermilfoil in the lakes of the Outaouais region has increased gradually since early
2001. Outdated septic systems, the construction of numerous lakeside buildings, wharfs, boathouses, lakeside
deforestation, lawn maintenance, and the use of fertilizers are among the many factors that can directly affect
the water quality of lakes and promote the establishment and proliferation of invasive species such as the
Eurasian watermilfoil.
The Lac St-Pierre Association was established in 1943 and its mission is to raise awareness of and educate the
property owners, residents, and visitors of Lac St-Pierre and Lac McMullin on the importance of keeping the
environment clean and maintaining the natural balance of the aquatic ecosystems in the two lakes. The
Association is made up over 200 lakeside members. Because the Lac St-Pierre Association is concerned with the
water quality of the lake and the increase in invasive aquatic plants, it has appointed ecology consultant Mélanie
Renaud to carry out this feasibility study with the goal of implementing a Eurasian watermilfoil control system in
order to restrict their growth by means of extended aeration.
This study will include a comprehensive overview of Lac St-Pierre; the diagnosis and identification of the causes
of the Eurasian watermilfoil invasion problem; control methods; feasibility of proposed control systems;
environmental impacts; required approvals; available resources as well as the other sources of solutions; and
recommendations. The purpose is to help the Association in making an informed decision on the best way to
solve the problem. This project is thus not only a feasibility study but also a key stepping stone for obtaining a
certificate of authorization to implement the recommendations.
Page 1
LAC ST-PIERRE OVERVIEW
Lac St-Pierre Overview
THE WATERSHED
Lac St-Pierre is located in the municipality of Val-des-Monts, about 35 kilometres north of the City of Gatineau.
Lac St-Pierre is one of the main lakes of Val-des-Monts and is a part of the watershed of the West Blanche River
which empties into the Ottawa River in the City of Gatineau. The Lac St-Pierre watershed has a surface area of
9 557 hectares, or the whole area that feeds this lake and is bounded by topographical features determining the
drainage divide.
According to the inventory produced by the Federation of Lakes of Val-Des-Monts in 2013 as part of the project
for integrated lake water management of Val-des-Monts watershed, Lac St-Pierre is fed by 10 tributaries and one
outlet that discharges in Lac McArthur on the southeast side of the lake.
TOPOGRAPHY
The Lac St-Pierre watershed consists of hills with a maximum height of 415 metres. The minimum height is about
167 metres (lake water level). Therefore, the difference between the hilltop and the outflow of the lake is 248
metres.
These topographical variations are important data since they are also an indicator of soil susceptibility to erosion.
Actually, the height, inclination, and length of the slopes are directly linked to the speed of the runoff and,
consequently, to shore erosion.
The nature of surface deposits and soil porosity also influence soil susceptibility to erosion.
The northeast shoreline is made up of fertile soil covering a layer of clay. This well-drained soil follows the gentle
slopes. Elsewhere, the lake shores appear to be made up of sandy and rocky soil.
GENERAL PHYSICAL CHARACTERISTICS
Lac St-Pierre has a maximum length of 6.8 kilometres and a maximum width of 0.8 kilometres, and it looks like an
upside-down “T ”. The Lac St-Pierre drainage basin contains 35 lakes, including: Lac des Mauves, Lac du Marbre,
Lac McMullin, Lac Clair, Lac de l'Écluse, and Lac Newcombe. Each one of these lakes flows into the southwestern
bay of Lac St-Pierre. The Lac St-Pierre outflow pours into Lac McArthur by way of the river located in the
southeastern bay, passes through several lakes (Lac Grand, Lac Dam, Lac Brassard, Lac McGregor), and finally
ends up in the West Blanche River which flows into the Ottawa River.
The perimeter of the lake is around 28 115 metres long and almost completely developed except for the very
steep section in the southwest. However, the uninhabited area is currently sought-after by a real estate
developer.
Page 2
The municipal zoning plan (see Figure 3) shows that almost all the land surrounding Lac St-Pierre is considered a
residential district, with the exception of a small section to the northwest which is considered a local commercial
district.
Table I. Physical characteristics of Lac St-Pierre
Geographical coordinates
Watershed area
Lake surface area
Elevation
Maximum depth
Average depth
Volume
Perimeter
Page 3
45°43’04.93’’N 75°42’30.34’’O
9557 hectares
386 hectares
167 metres
58 metres
14 metres
54 310 200 cubic metres
28 115 metres
Figure 1. Topographic map of Lac St-Pierre.
Page4
Figure 2. Bathymetric chart of Lac St-Pierre.
Page5
LIST OF USES
History and use
Located near Gatineau and the national capital region, Lac St-Pierre has experienced significant anthropogenic
pressure caused by lakeside residential development over the past 50 years. These changes can be seen clearly in
the following aerial photos and satellite images. Construction of access roads and lakeside homes and loss of
farmland is also evident.
The MRC des Collines implemented an interim by-law to enforce the applicable provisions for the protection of
shores, lakes, and streams. It stipulates that a strip of land for shoreline renaturalization will be established five
metres from the lake shore or stream (three metres in the case of a farm).
Figure 3. Zoning plan for the municipality of Val-des-Monts. Source: http://val-desmonts.net/en/site.asp?page=element&nIDElement=2915
Page6
Figure 4. Comparison between aerial photo Q66101-167 taken in 1966 and Google Earth Pro satellite image taken
in October 2013 of the northern bay of Lac St-Pierre. There is a noticeable increase in aquatic plants near the
shores of the lake.
Page7
in October 2013 of the centre of Lac St-Pierre.
Page8
in October 2013 of Primeau Bay in the southwest of Lac St-Pierre. The borrow pit operation south of the lake has
expanded.
Page9
Figure 7. Comparison between aerial photo Q66101-167 taken in 1966 and Google Earth Pro satellite image taken in October 2013 of
Desormeaux Bay in the southeast of Lac St-Pierre. There are submerged aquatic plants in the narrowest part of the bay in both images.
Page10
Tourist activities
There is a public boat launching ramp on the north bay of Lac St-Pierre. This ramp has been regulated since 2011
under the “Règlement sur les rampes de mise à l’eau” (Boat launching ramp by-law) BY-LAW NUMBER 741-13 of
the Municipality of Val-des-Monts. One item this by-law stipulates is that any Wakeboard-style boat with ballast
tanks or another device inside the hull which enters the water in a way that creates larger waves is not permitted
to use boat launching ramps. In addition, no motorized personal watercrafts are permitted to use the boat
launching ramps. Anyone who contravenes any provision of this by-law is committing an offence and would be
subject to a fine from a minimum of $300 to a maximum of $1 000. For repeat offenders, the fine is increased to
a minimum of $600 and a maximum of $2 000. However, the public boat launching ramp does not yet have a boat
wash station.
The boat launching ramp is also a great area for fishing enthusiasts from the region and from surrounding areas.
A wide variety of fish can be found, such as lake trout, brook trout, smallmouth bass, yellow perch, and brown
bullhead.
There is a water ski school on the lake as well where people practice sports like water skiing, wakeboarding,
slalom, and even diving with a diving board directly on the lake.
Figure 8. Excerpt from the interactive map “Allons pêcher” (Let’s go fishing) by the Fédération québécoise des
chasseurs et pêcheurs (Quebec hunting and fishing federation).
Page11
In addition, there is a public beach on the south side of the lake near the metal bridge that crosses the southwest
bay. This beach accommodates plenty of swimmers of all ages throughout the summer.
Figure 9. Public beach on Lac St-Pierre, Val-des-Monts
With regard to agriculture, there is a hog farm on the southwestern bay on Peabody Road. This farm is not a
lakeside property but borders one. Furthermore, there are several crop farms mostly in the north and east central
parts of the lake. As in the case of the livestock farm, these farms are not located on any Lac St-Pierre lakeside
land.
Figure 10. Hog farm in the southwestern part of Lac St-Pierre.
Page12
WATER QUALITY
Surface water quality criteria
The Quebec surface water quality criteria are mainly concerned with the protection of aquatic life, recreational
activities, and visual aspects of the environment. The parameters listed have been evaluated in specific places in
the watershed northwest of the West Blanche River. The temperature, dissolved oxygen, pH, specific
conductance, and nitrate parameters were collected at every metre or half-metre from the deepest spot (or from
the centre of the lake when the bathymetry is unknown) in each bay in the study. These parameters were
measured on July 31, 2013. The instrument used was a Pro Plus YSI, a multi-parameter probe. Water
transparency was measured with a Secchi disk in accordance with the Volunteer Lake-Monitoring Program water
transparency measuring protocol of the Department of Sustainable Development, Environment and the Fight
against Climate Change. The analyses and data compilations of the total phosphorus and fecal coliforms had been
carried out by volunteers from the lake association since 2000.
PARAMETERS
Temperature and dissolved oxygen
The dissolved oxygen varies according to the temperature of the water. In fact, there is more dissolved oxygen in
cold water than warm water. Other factors that may affect the amount of oxygen include altitude, barometric
pressure, time of day, lake depth, as well as concentrations of organic matter, nutrients, bacteria, algae, and
aquatic plants. Moreover, atmospheric dispersion and photosynthesis are the main natural processes that
contribute to the presence of dissolved oxygen in water.
Measuring the level of dissolved oxygen in a lake is helpful in assessing the health of the aquatic life and the lake.
According to the surface water quality criteria issued by the Department of Sustainable Development,
Environment and the Fight against Climate Change, in order to protect the aquatic life, dissolved oxygen
concentrations should not fall below the following numbers:
Page13
Table II. Water quality criteria for
dissolved oxygen concentrations
Temperature (°C)
Dissolved oxygen
(mg/L)
0
8
5
7
10
6
15
6
20
5
25
5
pH
The pH of the water was tested to determine its level of acidity. The pH scale ranges from 0 to 14 where 0 is very
acidic, 14 is very basic and 7 is neutral. The ecosystem of a lake is greatly influenced by the pH and needs to
remain at a neutral level (between 6 and 9) to survive.
Under acidic conditions, living organisms can have difficulty breathing and/or reproducing since these conditions
facilitate the release of toxic heavy metals (copper, mercury, lead) in the sediments, making them available and
absorbable. The pH level can also affect the amount of nutrients such as phosphorus and nitrogen in the water.
According to surface water quality criteria issued by the Department of Sustainable Development, Environment
and the Fight against Climate Change, a pH of 6.0 to 9.5 is necessary to meet requirements for the protection of
aquatic environments. For the protection of recreational activities and visual aspects of the environment, and to
be able to swim in it, the pH of the water must be between 5.0 and 9.0. With regard to the chronic effects on
aquatic life, the following table summarizes the lethal effects of pH values on fish.
Page14
Table III. Summary of the lethal effects of pH values on fish. Source: Water Quality Criteria for Freshwater Fish
(Alabaster and Lloyd 1982)
pH Range
3.0–3.5
3.5–4.0
4.0–4.5
4.5–5.0
5.0–6.0
6.0–6.5
6.5–9.0
9.0–9.5
9.5–10.0
10.0–10.5
10.5–11.0
11.0–11.5
Effect
Unlikely that any fish can survive for more than a few hours in this range although some
plants and invertebrates can be found at pH values lower than this.
This range is lethal to salmonids. There is evidence that roach, bream, perch and pike
can survive in this range, presumably after a period of acclimation to slightly higher,
non-lethal levels, but the lower end of this range may still be lethal for roach.
Likely to be harmful to salmonids, tench, bream, golden shiner, sea bream and common
carp which have not previously been acclimated to low pH values, although the
resistance to this pH range increases with the size and age of the fish. Fish can become
acclimated to these levels, but of perch, bream, roach and pike, only the last named
may be able to breed.
Likely to be harmful to the eggs and fry of salmonids, and to adults particularly in soft
water containing low concentrations of calcium, sodium and chloride. Can be harmful to
common carp.
Unlikely to be harmful to any species unless either the concentration of free carbon
dioxide is greater than 20 mg/L, or the water contains iron salts which are freshly
precipitated as ferric hydroxide, the precise toxicity of which is not known. The lower
end of this range may be harmful to non-acclimated salmonids if the calcium, sodium
and chloride concentrations, or the temperature of the water are low, and may be
detrimental to golden shiner reproduction.
Unlikely to be harmful to fish unless free carbon dioxide is present in excess of
100 mg/L.
Harmless to fish, although the toxicity of other poisons may be affected by changes
within this range.
Likely to be harmful to salmonids and perch if present for a considerable length of time.
Lethal to salmonids over a prolonged period of time, but can be withstood for short
periods. May be harmful to the developmental stages of some species.
Can be withstood by roach and salmonids for short periods but lethal over a prolonged
period.
Rapidly lethal to salmonids. Prolonged exposure to the upper limit of this range is lethal
to carp, tench, sea bream and pike.
Rapidly lethal to all species of fish.
Electrical conductivity
Conductivity is used to measure the water’s ability to conduct an electric current through ions found in the water.
The more ions there are in the water, the stronger the conductivity will be. Bicarbonate, calcium, chloride,
magnesium, potassium, and sulphate are all ions. The main natural and anthropogenic factors which can affect
the conductivity of lake water are the geology, groundwater flow, water temperature, lake evaporation, variation
in water flow, and contaminants from human activity. For example, the de-icing salt used on roads can affect the
electrical conductivity of a lake.
The electrical conductivity of lake water is measured with a conductivity meter in microsiemens per centimetre at
a standard temperature of 25°C. The electrical conductivity must be below 200 µS/cm for all freshwater lakes.
Page15
Nitrates
Nitrates are the salts of nitric acid. An excess of nitrates in the water may be a sign of pollution from an
anthropogenic source (agricultural, urban, or industrial). The unit of measurement for nitrate levels is mg/L. To
prevent contamination of the water and aquatic organisms, the total concentration of nitrate must not exceed
10 mg/L. For the protection of aquatic life, this criterion is constantly adjusted in relation to the surface water
quality criteria issued by the Department of Sustainable Development, Environment and the Fight against Climate
Change.
Transparency
Measuring the transparency of the water is a way to identify changes that may occur in the lake. Furthermore, it
is also possible to determine the trophic status (or ageing status) of the lake with the sampling of other
physicochemical properties of the water.
A Secchi disk is used to measure the transparency of lake water. The depth at which the Secchi disk is no longer
visible indicates the transparency of the water. For the protection of recreational activities and visual aspects of
the environment, the water must be clear enough so that the Secchi disk is visible up to a depth of at least 1.2
metres according to the surface water quality criteria issued by the Department of Sustainable Development,
Environment and the Fight against Climate Change. Table IV shows the transparency values according to each
trophic class.
Total phosphorus
Total phosphorus is a nutrient that is essential to the growth of plants and algae. It is found in our lakes at varying
concentrations. Therefore, there is a correlation between the phosphorus concentration, abundance of algae and
aquatic plants, and lake trophic levels. Eutrophic lakes, lakes at an advanced state of degradation and ageing,
generally have a higher phosphorus concentration.
Phosphorus sampling of the water is usually performed during the spring water overturn around one week after
the lake ice becomes fissured wedges. Phosphorus sampling can be performed several times throughout the year.
It must also be performed over a long period of time (several years) in order to identify trends in lake phosphorus
concentrations. Samples for these analyses are typically taken in the deepest part of the lake. Phosphorus
concentration is measured in micrograms per litre (µg/L) and the analysis must be carried out in a laboratory.
Table IV shows total phosphorus values for each trophic class. Every year, the water samples are collected by
volunteers from most lake associations and sent to the laboratory for analysis. The results are then sent to each
respective association as well as the Federation of Lakes of Val-Des-Monts, which compiles the information.
Page16
Table IV. Lake trophic classes with corresponding total phosphorus and transparency
values
Trophic class
Total phosphorus
Transparency
(µg/L)
(metres)
Primary classes
Secondary classes
Average
Average
(transition)
Ultra-oligotrophic
<4
> 12
Oligotrophic
4–10
12–5
7–13
6–4
10–30
5–2.5
20–35
3–2
Eutrophic
30–100
2.5–1
Hypereutrophic
> 100
<1
Oligo-mesotrophic
Mesotrophic
Meso-eutrophic
Fecal coliforms
Fecal coliforms are bacteria that indicate microbiological water pollution. These bacteria originate in fecal matter
produced by humans and warm-blooded animals. Their presence in a body of water indicates contamination
from fecal matter and its associated microbes. The Department classifies water quality based on the fecal
coliform content to determine if it is safe enough for recreational use. The following table shows the quality
requirements to protect public health according to the Department of Sustainable Development, Environment
and the Fight against Climate Change.
Table V. Water quality classification for recreational use
Water quality
Fecal coliforms /
Details
100 millilitres
Excellent
0 – 20
Suitable for all recreational
use
Good
21 – 100
use
Acceptable
101 – 200
use
Poor
More than 200
Unsuitable for swimming and
other direct contact with
water
Very poor
More than 1 000
Unsuitable for all recreational
use
Page17
Thermal stratification
Thermal stratification refers to the different superimposed layers of water in a lake that are distinguished by their
temperature and density. The three thermal stratification layers are the epilimnion (top layer), the metalimnion,
and the hypolimnion (bottom layer).
Figure 11. Thermal stratification. Source: lakeaccess.org and troussedeslacs.org
Eutrophication
Eutrophication is also considered a sign of lake ageing. Eutrophication is a natural and very gradual process that
can take place over thousands of years. However, human activity has accelerated the process to the point where
lakes have experienced eutrophication in only 10 years. Nutrient supplies such as nitrogen and phosphorus are
largely responsible for this ageing—in particular by upsetting the balance of ecosystems and increasing the
biological proliferation of aquatic plants and phytoplankton at the expense of many other aquatic species. This
process also contributes to the accumulation of sediment and organic matter, a decrease in dissolved oxygen, and
significant changes to the lake characteristics (disappearance of existing species and appearance of new species).
Lake eutrophication especially affects tourism.
Page18
Figure 12. The eutrophication process. Source: troussedeslacs.org
Other measurements
Dissolved organic carbon and chlorophyll-a concentrations and periphyton levels are other important parameters
for the accurate identification of a lake’s trophic status as well as for the analysis of the health status of a
watershed. These measurements are also taken by volunteers from the Volunteer Lake-Monitoring Program from
the Department of Sustainable Development, Environment and the Fight against Climate Change. Monitoring the
concentration of dissolved organic carbon (DOC) can help identify changes in the organic pollution from
decomposing plant and animal debris or anthropogenic contaminants. The brown or amber discoloration of the
water is caused by the DOC, which, in high concentrations, affects the quantity of dissolved oxygen.
The concentration of chlorophyll-a in a lake indicates the amount of microscopic algae in the water, which
increases with the concentration of nutrients and consequently the lake trophic level.
Periphyton presence is indicated by microscopic algae living on the surfaces of objects submerged in the water.
Lake enrichment adds to the presence and level of periphyton. Periphyton levels are measured every 3 years in
accordance with Volunteer Lake-Monitoring Program periphyton monitoring protocol from the Department of
Sustainable Development, Environment and the Fight against Climate Change.
Page19
Water quality of Lac St-Pierre
The Federation of Lakes of Val-Des-Monts has
been compiling the data from total phosphorus
sampling since 2000. Note that there was no
sampling in 2002 and 2010. Total phosphorus
sampling is carried out by Lac St-Pierre
Association members and by Federation of Lakes
coordinators during certain years. The water
samples are usually taken during the spring
water overturn. Overall, the average results
indicate that the lake’s trophic class is oligomesotrophic, with the actual results ranging
from oligotrophic to mesotrophic. Only the
northern bay is exclusively mesotrophic.
4
3
1
Figure 13. Locations of total phosphorus and
water transparency sampling sites.
6
Trophic class
5
Total phosphorus
(µg/L)
Average
Transparency
(metres)
Average
Ultra-oligotrophic
<4
> 12
Oligotrophic
4–10
12–5
7–13
6–4
10–30
5–2.5
20–35
3–2
Eutrophic
30–100
2.5–1
Hypereutrophic
> 100
<1
Primary classes
Secondary classes
(transition)
Oligo-mesotrophic
Mesotrophic
Meso-eutrophic
Table VI. Lake trophic classes with corresponding total phosphorus and transparency values
Page 20
2
The following tables and figures show the summary of all the results as well as the linear prediction trendlines of
the total phosphorus for each sampling site in Lac St-Pierre. In all, 6 sites were used for sampling and each site
shows an upward trend since the beginning of the sampling.
TableVII.Averagetotalphosphorus- Site1
30
25
20
18.0
15
10
7.3
6.7
0
April26,2009
May5,2013
5
May18,2014
TableVIII.Averagetotalphosphorus- Site2
25
21.3
20
18.3
15.7
15
8.3
7.3
5
13.0
12
11
10
4.3
6.7
6.3
8.0
7
0
26
Mai
23 6mai 4mai 5mai 29 4mai 26 6mai 11 5mai 18mai
avril 2001 avril 2004 2005 2006 avril 2008 avril 2011 avril 2013 2014
2000
2003
2007
2009
2012
TableIX.Averagetotalphosphorus- Site3
25
23.7
20
17.3
15
12.7
10
Page21
9.7
9.3
5
0
16.3
15
11
8.0
4.7
0
26avril Mai 23avril 6mai
2000 2001 2003 2004
4mai
2005
5mai
2006
4mai
2008
6mai 11avril 5mai 18mai
2011 2012 2013 2014
Table X. Average total phosphorus - Site 4
25
22.3
20
15
16.3
14
13.3
10.7
10
10.0
5
0
May 4, 2008
April 26,
2009
May 6, 2011
April 11,
2012
May 5, 2013
May 18,
2014
Table XI. Average total phosphorus - Site 5
20
15
14.3
10
8
6.3
6
5
7.7
0
April 29, 2007 May 4, 2008 April 26, 2009 May 5, 2013 May 18, 2014
Table XII. Average total phosphorus - Site 6
25
20
15
10
5
0
19.3
16
9.7
7.3
6
2
10.3
9
4
3.5
12.0
5
26 1 Mai 23 6 mai 4 mai 5 mai 29 4 mai 6 mai 11 5 mai 18 mai
avril 2001 avril 2004 2005 2006 avril 2008 2011 avril 2013 2014
2000
2003
2007
2012
Date
Table XIII. Summary of total phosphorus results for Site 1
Average total phosphorus
Total phosphorus (mg/L)
April 26, 2009
May 5, 2013
May 18, 2014
Page22
7.3
6.7
18.0
8
7
17
6
6
19
8
7
18
Table XIV. Summary of total phosphorus results for Site 2
Date
April 26, 2000
7.3
6
7
9
May 2001
15.7
18
14
16
April 23, 2003
8.3
10
10
5
May 6, 2004
11
12
11
10
May 4, 2005
4.3
2
4
7
May 5, 2006
6.3
6
7
6
April 29, 2007
12
12
10
14
May 4, 2008
6.7
7
7
6
April 26, 2009
7
7
7
7
May 6, 2011
21.3
21
20
23
April 11, 2012
18.3
19
20
16
May 5, 2013
8.0
8
9
7
May 18, 2014
13.0
12
13
14
Date
Table XV. Summary of total phosphorus results for Site 3
April 26, 2000
May 2001
April 23, 2003
May 6, 2004
May 4, 2005
May 5, 2006
May 4, 2008
May 6, 2011
April 11, 2012
May 5, 2013
May 18, 2014
9.3
17.3
<2
12.7
4.7
9.7
11
15
23.7
8.0
16.3
9
16
<2
13
6
10
11
13
26
8
20
10
18
<2
12
4
10
11
14
22
8
14
9
18
<2
13
4
9
11
18
23
8
15
Table XVI. Summary of total phosphorus results for Site 4
Page 23
Date
May 4, 2008
13.3
13
13
14
April 26, 2009
14
14
14
14
May 6, 2011
10.7
11
11
10
April 11, 2012
22.3
21
23
23
May 5, 2013
10.0
10
10
10
May 18, 2014
16.3
16
16
17
Table XVII. Summary of total phosphorus results for Site 5
Date
April 29, 2007
6
6
4
8
May 4, 2008
6.3
6
5
8
April 26, 2009
8
7
9
8
May 5, 2013
7.7
7
8
8
May 18, 2014
14.3
14
12
17
Date
Table XVIII. Summary of total phosphorus results for Site 6
April 26, 2000
May 1, 2001
April 23, 2003
May 6, 2004
May 4, 2005
May 5, 2006
April 29, 2007
May 4, 2008
May 6, 2011
April 11, 2012
May 5, 2013
May 18, 2014
Page24
7.3
16
2
9.7
6
9
4
3.5
5
19.3
10.3
12.0
11
16
<2
13
4
6
4
<2
5
20
11
12
5
13
<2
8
6
13
4
4
5
19
14
12
6
18
<2
8
8
8
4
3
5
19
6
12
Analysis of physicochemical profiles for the northern bay (Site 4) of Lac St-Pierre
The following graph shows the physicochemical profiles collected on July 23, 2013, for Site 4, the northern bay of
Lac St-Pierre. Table XIX illustrates the raw data. Note that the interpretation of the physicochemical profiles is
valid only for the sampling period (June 2013).
0
20
40
60
80
100
120
140
0
2
Depth
4
6
Température
(°C)
Oxygène
dissous
(mg/l)
Conductivité
(µS/cm)
pH
8
10
12
14
Figure 14. Graph of the physicochemical profiles of the northern bay showing the thermal stratification of the
water column.
The temperature profile of the lake for Site 4 shows that the lake was stratified when the sample was taken. The
temperature of the surface water was 25.7°C, gradually decreasing to 12.2°C at 13 metres from the surface—a
difference of 13.5°C. The thermal stratification shows three distinct layers: the epilimnion (top layer); the
metalimnion (transitional layer at 4–8 metres from the surface), where the most significant changes in
temperature occur; and the hypolimnion (bottom layer).
Oxygen
The oxygen dynamics of the northern bay of Lac St-Pierre show that the water column is well oxygenated up to 6
metres deep.
Page25
However, starting from 6.5 metres, the dissolved oxygen concentrations are below normal values according to the
surface water quality criteria issued by the Department of Sustainable Development, Environment and the Fight
against Climate Change for the protection of aquatic life, which places dissolved oxygen levels at 7 mg/L or more
for a temperature of 5 to 10°C.
This anoxia may be attributable to a variety of factors, including the following:
•
•
•
•
A partial spring water overturn preventing the lake from completely recharging its oxygen before the
onset of thermal stratification which can be caused by a change in water levels, flows from the
watershed, and changes in temperature (even climate).
A significant amount of nutrients and organic matter as a result of human activity in the watershed.
A significant amount of micro-organisms that use the available dissolved oxygen to break down the
nutrients and organic matter in the water.
The eutrophication of the lake.
Recommendation:ForabetterunderstandingofthedynamicsofdissolvedoxygeninLacSt-Pierreand
causesofanoxia,developmultiplephysicochemicalprofilesoverthesummerseasonandthenannually.
Photosynthesis and, consequently, oxygen production by aquatic plants cause the slight increase in the
concentration of dissolved oxygen observed at 5 metres from the surface. This is a frequently observed lake
phenomenon.
The data found for electrical conductivity, ranging from 99.1 to 120.9 µS/cm, are within the normal range for
fresh water (under 200 µS/cm).
pH
The pH values found for the sample water column fall between 6.6 and 6.8. These values are within the normal
range for the protection of aquatic life, recreational activities, and visual aspects of the environment.
Nitrate
The measurements for nitrate concentrations found in the Lac St-Pierre water fall between 0.45 and 0.89 mg/L.
The Department of Sustainable Development, Environment and the Fight against Climate Change has determined
that a concentration below 10mg/L is required for the prevention of water and aquatic organism contamination.
However, it is important to note that when used for the protection of aquatic life, this criterion is constantly
adjusted according to the surface water quality criteria issued by the Department of Sustainable Development,
Environment and the Fight against Climate Change.
Page26
Transparency
According to the measurements from July 23, 2013, the water transparency of Lac St-Pierre was 4.5 metres, a
value falling within the oligo-mesotrophic tropic class. However, there are also several other factors which
determine the trophic class of lake, not just transparency.
Depth (m)
Temperature
(°C)
1
2
3
4
5
6
7
8
9
10
11
12
13
25.7
25.7
25.7
25.6
18.5
13.1
12.3
11.7
11.7
11.8
11.8
11.8
12.2
Dissolved
oxygen
(mg/L)
7.9
8
8.1
8
11.3
6
4.9
0.5
0.4
0.3
0.3
0.3
0.3
Conductivity
(µS/cm)
pH
Nitrate
119.5
119.6
120
120.4
103
99.1
100
111
120.9
120
120
121
102.6
6.83
6.87
6.85
6.81
6.76
6.72
6.67
6.63
6.6
6.6
6.63
6.64
6.63
0.74
0.89
0.88
0.87
0.78
0.6
0.53
0.48
0.46
0.45
0.48
0.5
0.57
Table XIX. Physical chemistry results of the northern bay water column.
Page27
Analysis of physicochemical profiles for Desormeaux Bay (Site 1) of Lac St-Pierre
The following graph shows the physicochemical profiles collected on July 31, 2013 for Desormeaux Bay of Lac StPierre. Table XX illustrates the raw data. Note that the interpretation of the physicochemical profiles is only valid
for the sampling period, June 2013.
0.0
20.0
40.0
60.0
80.0
100.0
120.0
0
1
Température
(°C)
2
3
Depth
4
Oxygène
dissous
(mg/l)
Conductivité
(µS/cm)
5
6
pH
7
8
9
10
Figure 15. Graph of the physicochemical profiles of Desormeaux Bay showing the thermal stratification of the
water column.
The temperature profile of Desormeaux Bay shows that the lake was stratified when the sample was taken. The
temperature of the surface water was 23.4°C, gradually decreasing to 7.5°C at 9.1 metres from the surface—a
difference of 15.9°C. The thermal stratification depicts three distinct layers: the epilimnion (top layer); the
metalimnion (transitional layer at 3–7 metres from the surface), where the most significant changes in
temperature occur; and the hypolimnion (bottom layer).
Page28
Oxygen
The oxygen dynamics of Desormeaux Bay of Lac St-Pierre show that the water column is well oxygenated up to 6
metres deep.
However, starting from 6.5 metres, the dissolved oxygen concentrations are below normal values according to the
surface water quality criteria issued by the Department of Sustainable Development, Environment and the Fight
against Climate Change for the protection of aquatic life, which places dissolved oxygen levels at 7 mg/L or more
for a temperature of 5 to 10°C.
This anoxia may be attributable to a variety of factors, including the following:
•
•
•
•
A partial spring water overturn preventing the lake from completely recharging its oxygen before the
onset of thermal stratification which can be caused by a change in water levels, flows from the
watershed, and changes in temperature (even climate).
A significant amount of nutrients and organic matter as a result of human activity in the watershed.
A significant amount of micro-organisms that use the available dissolved oxygen to break down the
nutrients and organic matter in the water.
The eutrophication of the lake.
Photosynthesis and, consequently, oxygen production by aquatic plants cause the slight increase in the
concentration of dissolved oxygen observed at 4–6 metres from the surface. This is a frequently observed lake
phenomenon.
The data found for electrical conductivity, ranging from 78.6 to 102.5 µS/cm, are within the normal range for
fresh water (under 200 µS/cm).
pH
The pH values found for the sample water column fall between 6.8 and 7.2. These values are within the normal
range for the protection of aquatic life, recreational activities, and visual aspects of the environment.
Nitrate
The measurements for nitrate concentrations found in the Lac St-Pierre water fall between 0.56 and 1.25 mg/L.
The Department of Sustainable Development, Environment and the Fight against Climate Change has determined
that a concentration below 10mg/L is required for the prevention of water and aquatic organism contamination.
However, it is important to note that when used for the protection of aquatic life, this criterion is constantly
Page29
adjusted according to the surface water quality criteria issued by the Department of Sustainable Development,
Environment and the Fight against Climate Change.
Transparency
According to the measurements from July 31, 2013, the water transparency of Lac St-Pierre was 6.1 metres, a
value which falls within the oligotrophic tropic class. However, there are also several other factors which
determine the trophic class of lake, not just transparency.
Depth (m)
1
2
3
4
5
6
7
8
9.1
Temperature
(°C)
23.4
23.2
23.0
20.2
20.4
20.4
8.7
7.7
7.5
Dissolved
oxygen (mg/l)
6.9
7.1
6.7
9.6
12.3
10.0
5.7
1.7
0.5
Conductivity
(µS/cm)
102.5
102.1
102.4
100.0
88.0
81.5
78.8
78.6
79.5
Table XX. Physical chemistry results of the water column in Desormeaux Bay.
Page30
pH
Nitrate
7.11
7.22
7.14
7.06
6.99
6.93
6.88
6.85
6.82
1.25
1.18
1.22
1.14
1.00
0.86
0.72
0.62
0.56
DIAGNOSIS AND IDENTIFICATION OF THE CAUSES OF
THE EURASIAN WATERMILFOIL INVASION PROBLEM
DiagnosisandidentificationofthecausesoftheEurasian
watermilfoilinvasionproblem
AQUATIC PLANTS
There are four types of aquatic plants: submerged plants such as watermilfoils, common bladderworts,
pondweeds, and waterweeds; emerged plants such as pickerelweeds, arrowheads, and three-way sedges;
riparian plants such as sedges, sensitive ferns, pitcher plants, cattails, and sundews; and floating plants such as
water lilies, pond lilies, water-shields, and duckweeds.
Figure 16. Aquatic plants, 1= Northern pitcher plant, 2= Broadleaf arrowhead, 3= Fragrant water lily, 4=
Pickerelweed, 5= Eurasian watermilfoil.
Page31
INVASIVE AQUATIC PLANTS
The Eurasian watermilfoil invasion is a result of the introduction of the exotic species to the water. However,
some species of native aquatic plants are also invasive. The large-leaved pondweed and Robbins' Pondweed (see
Figure 17) are both examples of invasive native aquatic plants in Lac St-Pierre.
Figure 17. Large-leaved pondweed on the left and Robbins' Pondweed on the right.
The invasion of aquatic plants in a body of water is also due to the amount of nutrients in the water, especially
nitrogen and phosphorus, which promotes their growth. Nutrients may be supplied naturally from runoff water,
flooding, or beaver dam failures, and their natural presence in the surrounding substrate, but in most cases this
supply is minimal. Nutrients in a recreational lake are often supplied from human activity such as faulty, outdated
septic systems, the use of household products containing phosphorus, the use of fertilizers (natural or chemical),
composting for gardening and farming, feeding aquatic birds, deforestation, non-compliance with the shoreline
renaturalization strips, intensive wood harvesting in the watershed, and the reshaping and development of
waterways and drainage ditches.
Since these aquatic plants reproduce mainly through plant cuttings, the act of cutting part of the plant will lead to
the growth of a new plant in a short amount of time (see Figure 18). Therefore, the use of motorboats in aquatic
plant beds would greatly increase the proliferation of these invasive plants. Moreover, the risk of introducing
species from other lakes is a possibility because boat propellers are not properly cleaned before entering the lake.
Furthermore, Eurasian watermilfoil has been found in Lac McMullin, upstream of Lac St-Pierre. An exotic aquatic
plant invasion problem may also arise in lakes within the same watershed.
Page32
Figure 18. Eurasian watermilfoil plant cuttings with prominent roots. Lac Grand.
Figure 19. Eurasian watermilfoil bed. Lac St-Pierre.
In conclusion, the aquatic plant invasion problem is the result of multiple factors which promote their growth and
proliferation. Moreover, since these plants can only grow up to a depth of around 10 metres they prefer shallow
areas, where large plant beds can be found. Therefore, lake morphology is directly related to the availability of
plant nutrients as well as the presence and growth of plant beds.
Page33
Figure 20. Lake and watershed morphology. Source: www.crelaurentides.org
Page34
Figure 21. Aquatic plant beds located in Lac St-Pierre in July and August 2013.
Page35
CONTROL METHODS
ControlMethods
COMPARISON OF PROPOSED SYSTEMS
For this study, information on two types of aquatic plant control method systems was submitted to the Lac StPierre Association. These two systems are similar to “physical” control methods, and both consist of hypolimnetic
aeration by supplying oxygen to form a barrier that controls the release of phosphorus. However, the system
proposed by the company CLEAN-FLO International offers a combination of “physical” and “biological” control
methods.
CANADIANPOND.CA SYSTEM
The first aeration system is made by the company Canadianpond.ca. This system consists of the OctoAir-10™, a
circular industrial diffuser that can hold up to 30.5 metres of flexible PVC diffuser tubing perforated with two
rows of holes that release micro-air bubbles. According to Canadianpond.ca, two diffusers would be necessary to
control the aquatic plants in Desormeaux Bay, and six for the northern bay of the lake. The diameter of each
diffuser is 122 cm (48 in.). Each diffuser is powered by a compressor. A ventilated cabinet for the two
compressors (1/2 HP, double cylinder, 115 V, 4 A, and 50 psi) would be required to supply the two diffusers of
Desormeaux Bay, and two ventilated cabinets for six compressors would be required for the northern bay.
Compressed air is pushed through airline delivery hose to the OctoAir-10™ diffuser. Micro bubbles are
simultaneously released through the micro holes along the 100- foot length of Bubble Tubing™. An
extremely even bubble pattern releases high levels of oxygen, while creating important lift, mixing and
circulation of liquids such as leachate, sewage or potable water.
No moving parts or electricity in the water means very low operational costs. Source: Canadianpond.ca
If the aerator is used during the winter, the de-icing pattern should be clearly indicated with a sign to warn of
danger.
Page36
CONTROL METHODS
Figure 22. Locations of diffusers and cabinets for compressors. Source: Canadianpond.ca
Figure 23. Cabinets for compressors by Canadianpond.ca
Page 37
CONTROL METHODS
Figure 24. The OctoAir-10™ diffuser by Canadianpond.ca. Source: Canadianpond.ca
Page 38
CONTROL METHODS
LAKE SAVERS AND WEEDS B’ GONE SYSTEMS
The second aeration system is by the company Weeds B’ Gone, in partnership with the companies CLEAN-FLO
International and Lake Savers. This system essentially consists of the same components as the as the previous
system since it uses diffusers connected to compressor cabinets located on the shore to aerate the hypolimnion
of the lake. This system also consists of mechanical lake weed harvesting combined with an aeration system and
the injection of aerobic bacteria in aerated areas.
Figure 25. The different components of the Weeds B’ Gone aeration system. Source: weedsbgone.co
A system installed on the shore can cover an area of about 30 metres by 30 metres (100 ft. x 100 ft.) when the
lake depth is 1.2 to 2 metres. The system includes five 8-inch non-turbulent diffusers, a 3/4 HP compressor, a
cooling fan insulated in a fiberglass cabinet, and approximately 500 feet of self-sinking 5/8 tubing.
Page39
CONTROL METHODS
Figure 26. C-FLO formula of microorganisms. Source: weedsbgone.com
The system can be combined with C-FLO, a special formula of microorganisms that feed on organic sediment.
This formula works best in a lake that is continuously oxygenated, because if the oxygen runs out, the lake will
need a new application. For best results, it is recommended to use the formula in combination with the enzyme
formula explained below.
The C-FLO should be used about 2 weeks after the start of the aeration system. C-FLO is applied at a rate of 1
pound per acre 2 to 4 times a year by spreading the formula evenly on the surface of the lake when the water is
at a temperature of 13°C.
Figure 27. Clean and Clear concentrated enzyme formula. Source: weedsbgone.com
The Clean and Clear formula is a concentrated blend of non-toxic vegetable enzymes that acts as a catalyst to
accelerate the biodegradation of organic matter and reduce available nutrients in the water. In short, it makes it
easier for aerobic bacteria to digest organic matter. To use it, simply apply 1 gallon per acre.
Page40
CONTROL METHODS
Figure 28. Diatoms (phytoplankton). Source: lake-savers.com
Another recommended formula by Weeds B’ Gone is “Nualgi Lakes” which adds diatoms to the lake. Diatoms are
actually a type of phytoplankton that converts the carbon dioxide, nitrogen, and phosphorus in the water into
oxygen. They are also competing with other algae in the water such as cyanobacteria (blue-green algae) and
filamentous algae by reducing the availability of nutrients in the water. Thus, Nualgi Lakes is a product used for
diatom regeneration. To use it, simply apply 1 litre per acre per week for 2 weeks. After this, the application rate
is reduced to 1 half-litre per acre per week for 4 to 6 weeks.
Figure 29. The Weeds B’ Gone aeration system in action. Source: weedsbgone.com
Page41
CONTROL METHODS
HYPOLIMNETIC AERATION USING OXYGEN
Hypolimnetic aeration using oxygen is mainly used to make the water intake accessible and free of aquatic plants
and/or to make the water safe for consumption (free from cyanobacteria and others); to improve or maintain the
beauty of the lake; to prevent health risks related to the consumption of contaminated fish; and to maintain or
restore access for motorboats and preserve “indirect contact” activities such as fishing, canoeing, and
recreational boating.
The duration of the effect of this method is considered medium-term.
Advantages
Hypolimnetic aeration controls the release of phosphorus and other nutrients from the sediment.
Disadvantages
Hypolimnetic aeration is effective only in the area where it is used. The thermal destratification of the lake
(making the temperature at the bottom the lake the same as the surface) where the aeration is used can lead to
fish kills. Finally, aeration during winter can result in a lack of ice or a thin, brittle layer of ice which could lead to
drowning.
Condition of acceptance and mitigation measures
Hypolimnetic aeration is used for small-area lakes at depth of 5 metres or less. The Department of Sustainable
Development, Environment and the Fight against Climate Change could allow the use of this method if the
stratification is maintained and if tests indicate that biological communities will not be affected.
BIOAUGMENTATION
Bioaugmentation (injection of aerobic bacteria) is mainly used to improve or maintain the beauty of the lake; to
prevent health risks from direct contact with the water and ensure the safety of lake activities (swimming,
windsurfing, kayaking); to maintain or restore access for motorboats and maintain “indirect contact” activities
such as fishing, canoeing and recreational boating; and to protect or restore the aquatic life of natural
communities (fish, invertebrates, zooplankton, algae and native macrophytes).
The duration of the effect of this method is considered medium-term.
Advantages
Bioaugmentation reduces algae growth, improves water transparency, eliminates odors, and breaks down the
organic matter in the water. It acts in different ways because the phosphorus is absorbed in the bacterial cell wall,
the nitrogen begins nitrification, and the nitrite and ammonia are oxidized by dissolved oxygen.
Page42
CONTROL METHODS
Disadvantages
Bioaugmentation should be combined with an aeration method or it will result in the death of the bacteria. This
treatment requires a high pH (7.5 to 9—highly alkaline) and a water temperature of at least 12°C to be effective.
The optimal water temperature for bacteria is 30°C.
Therefore, this treatment is ineffective in Quebec because the average temperatures are too low and it is difficult
to apply to large areas.
Bioaugmentation is a technique developed for use in the treatment of domestic wastewater as well as the
treatment of fish-farming water. It should only be considered for the treatment of small bodies of water. The pH,
alkalinity, and water temperature should be checked and must meet the treatment requirements for adequate
efficacy.
MECHANICAL CUTTING OR HARVESTING
Mechanical cutting or harvesting of aquatic plants is usually performed using a weed-cutter and is primarily used
to make the water intake accessible and free of aquatic plants and/or to make the water safe for consumption
(free from cyanobacteria and others); to improve or maintain the beauty of the lake; to prevent health risks from
direct contact with the water and ensure the safety of lake activities (swimming, windsurfing, kayaking); and to
maintain or restore access for motorboats and maintain “indirect contact” activities such as fishing, canoeing and
recreational boating.
The duration of the effect of this method is considered short-term.
Advantages
This method will immediately open the lake and remove only the surface plants. It is adapted to hydrophytes;
thus, it partially preserves the habitat for aquatic wildlife. It is also more cost-effective.
Disadvantages
This method is non-selective and disturbs the aquatic life which could also disturb the sediments on the bottom
of the lake. This method often destroys small fish, benthic invertebrates, and other species in the surface parts of
plants. It can also contribute to the proliferation of species (from cuttings) if the plants are not completely
removed. This method requires a minimal water depth and has limited effectiveness when plants begin to wither.
Page 43
CONTROL METHODS
This method should be avoided during fish spawning and nesting periods. The location of the site must be readily
accessible to avoid damaging the shores, and the harvesting area must clearly identified with buoys to optimize
the work. This method is helpful only when the water is completely invaded and cutting is performed during the
plant flowering and germination periods in order to weaken them for the following seasons. Finally, it is essential
to establish a recovery system of all plant fragments.
COMPARISON OF SYSTEMS
As previously mentioned, the two companies overall use a similar aeration system, except the Canadianpond.ca
system offers the additional micro-bubble aeration in the tubing leading to the diffuser (OctoAir-10™). The
specifications of the different components of the Canadianpond.ca system are described better than those of
Weeds B’ Gone.
Moreover, the system proposed by Canadianpond.ca only uses hypolimnetic aeration. The diffuser is also a look
at industrial-grade.
With regard to the Weeds B’ Gone system, this company offers a combination of methods to ensure the
effectiveness of the system. Aeration is combined with bioaugmentation and harvesting. The management of
system requires more labour and/or volunteers. In addition, the product would have to be purchased several
times if we want to follow the suggested protocol. Finally, a cutter-boat or other similar mechanical devices will
be required for plant harvesting.
COSTS
In terms of costs, only one proposal was made by Canadianpond.ca with total costs that work out to about
$32,300 for the treatment of the northern bay which includes two cabinets and six compressors and about
$11,400 for the treatment of Desormeaux Bay which includes one cabinet with two compressors for the aeration
system, and a 5-year warranty.
However, Weeds B’ Gone offers a simulation of the breakdown of costs by using Lake Greenwood in the state of
New York as an example. There were 80 treatments carried out at strategic locations in a stretch of about 9.5 km
along the lake. A CLEAN-FLO aeration system was used, bacteria and enzymes (by CLEAN-FLO) were also used as
well as a harvesting treatment over 5 days. The aeration equipment cost amounted to $6,200 and included a 3/4
HP compressor in an insulated cabinet, five 8-inch diffusers, and 550 feet of tubing with fittings. For the same
diameter, six Weeds B’ Gone diffusers would be equivalent to one Canadianpond.ca OctoAir-10™ diffuser (48 in.
diffuser). The proposal from Canadianpond.ca offers a total of 8 diffusers for the treatment of the two bays.
Therefore, it would take about 48 Weeds B’ Gone diffusers to match the surface covered by the Canadianpond.ca
aeration system. Since one compressor powers five diffusers, we will estimate that the number of diffusers is 50
for this calculation. So the purchase of 10 compressors at $6,200 each would amount to a total of $62,000. The
bioaugmentation products (diatoms, enzymes and bacteria) also add another $450 for a single treatment of 1
acre. The northern bay alone is about 150 acres, and Desormeaux Bay is about 50 acres, for a total of about 200
Page 44
CONTROL METHODS
acres. That would mean that the costs to perform an effective treatment of these 200 acres would be truly
exorbitant and unrealistic.
Figure 30. Comparison of Lac St-Pierre in Val-des-Monts and Lake Greenwood in New York at the same scale.
Page45
FEASIBILITY OF PROPOSED CONTROL SYSTEMS
Feasibilityofproposedcontrolsystems
EXPECTED EFFICIENCY AND SUCCESS
The proliferation of aquatic invasive plant beds is partially the result of conditions conducive to their
establishment and proliferation. These conditions can be found in shallow coastal areas where a sufficient layer
of sediment made up of organic matter is present. To date, no “miracle” method has yet proved to be fully
effective. All methods currently available still require solid documentation and experimental studies to evaluate
all the parameters of the problem. The hypolimnetic aeration control method is the main method proposed by
the companies subject to this feasibility study.
SIMILAR SITUATIONS
Other lakes that used the aeration control method seem to have achieved some success in controlling and even
locally eradicating the Eurasian watermilfoil and invasive aquatic plants. This is the case for Lake Lola, located in
the municipality of La Pêche. The lake’s Eurasian watermilfoil population almost disappeared at the locations of
the two diffusers (aerator rock), which are supplied by a land-based wind turbine and then by a micro-bubble
diffuser tube for the section along the main road. Moreover, the lakeside residents even noticed the return of
native and non-invasive aquatic plants. Lac Hotte, located in the municipality of St-André d’Avellin, is another lake
that is implementing a system of land-based wind turbines with diffusers. The president of the Association des
propriétaires du lac Hotte (Lac Hotte Owners Association) claims to have noticed a decrease in watermilfoil beds
since the installation of three wind turbines with diffusers in the fall of 2013, even if no scientific study was
carried out just before the installation of the wind turbines. This association also plans to install another four
wind turbines when funding will be available. However, note that these lakes are smaller than Lac St-Pierre. At
Lac Carré in St-Faustin-le-Carré, the Speece Cone, a hypolimnetic aeration system, was installed in 2002. This
system proved to be ineffective at increasing the level of dissolved oxygen in the hypolimnion; however, several
factors may be the reason for this. Moreover, since 2009 and the lowering of the lake level for two consecutive
winters, there has been a decrease in watermilfoil bed, but sometimes it reaches the surface on the north side of
the lake.
Page46
Figure 31. Speece Cone system used on Lac Carré. http://www.eco2tech.com/works.php
The municipal council of Lantier has formalized the purchase of three SUNGO VI solar-powered aerators/water
pumps from Eco-Guide International Inc. Using this technology, the Municipality of Lantier wants to improve the
water quality of Lac Ludger and Lac Cardin, thereby controlling the spread of invasive plants such as Eurasian
watermilfoil. These devices were used at Lac Pointe-Calumet (Super Aqua Club of Pointe-Calumet) and at Lac
Papineau (Petit Lac Long) in Sainte-Agathe-des-Monts. However, the results provided by this device will not be
known until next spring.
Figure 32. SUNGO VI solar-powered aerators/water pumps from Eco-Guide International Inc. Source:
http://municipalite.lantier.qc.ca/index.php/79-nouvelles/73-myriophylle-a-epis
Taking into account the preceding information, it is clear that the currently available solutions on the market are
technologies that are still at an experimental stage. Each of the lakes have different characteristics, the climate
may even differ from one region to another thus affecting the desired results of the test equipment.
Page47
LAC ST-PIERRE AND HYPOLIMNETIC AERATION
At first, the Lac St-Pierre Association only wants to use a control method in the northern bay and Desormeaux
Bay. Even though hypolimnetic aeration is mainly used on smaller lakes, this method could be considered for
localized use in each bay. It could also address the issue of hypolimnetic anoxia observed in the dissolved oxygen
results of the physical chemistry of these two bays in 2013.
However, considering the costs and constraints associated with this method, it is recommended to start testing
the hypolimnetic aeration method only at Desormeaux Bay since a smaller number of people use motorboats in
that bay. The outlet of Desormeaux Bay is a favorite spot for boaters and kayakers who use this waterway to get
from Lac St-Pierre to Lac McArthur and back. Residents also enjoy swimming in several areas of the bay. Because
of the weighted micro-bubble tubing, the aeration system by Canadianpond.ca seems to be most effective since it
produces an “air curtain” along the tubing in addition to the diffuser itself, which cover a larger area. The
installation of a large diffuser is easier than installing six small diffusers. The tubing system can reduce the risk of
collision as well. It would be a good idea to use buoys throughout Desormeaux Bay to indicate the areas treated
by the aeration system and where the use of motors is prohibited. If prohibiting the use of motors is not possible,
buoys indicating speed limits should be placed in the bay.
Figure 33. Examples of buoys to install in Desormeaux Bay. Source:
http://www.nordakmarine.ca/fr/bouee-riveraine.php
Page48
With regard to the northern bay, it is recommended to wait to see the results at Desormeaux Bay after about two
years of use. The increased use of motorboats at the northern bay due to the public boat-launching ramp is
proving to be an additional hurdle in eliminating and reducing Eurasian watermilfoil in this sector. Before setting
up a hypolimnetic aeration system, a motorboat corridor must be determined and marked by buoys to avoid
traffic in the aquatic plants beds areas. It is also recommended to install a high-pressure boat wash station.
Furthermore, it is recommended that aeration continues not only during summer but throughout the year to
exhaust the plants by hindering their dormancy and extending the chlorophyll production period that is normally
stopped by the ice (sunlight cannot penetrate the ice). However, winter use of hypolimnetic aeration could be
dangerous for humans and some animals if they venture into these areas—the ice can be very thin or even
absent—therefore, it will be very important to have signs indicating the danger. Alternatively, it is possible to
remove the devices for the winter, but the effectiveness will be reduced.
BIOAUGMENTATION
With regard to the bioaugmentation (addition of bacteria, enzymes, and diatoms) proposed by Weeds B’ Gone,
this method is not recommended. The reason for this recommendation is based on the climatic zone and pH
levels specific to Lac St-Pierre. For bioaugmentation to be effective, the water temperature must remain above
12°C, considering that these bacteria have an optimal efficiency at 30°C. However, the water column measured in
the northern bay on July 31, 2013 showed temperatures between 11.8°C, at a depth of 10 metres, and 25.7°C, at
the surface. The temperatures in Desormeaux Bay water column varied from 7.5°C, at a depth of 9 metres, to
23°C, at the surface. In addition, the survival of these bacteria requires constant aeration and high pH (7.5 to 9).
However, the northern bay of Lac St-Pierre had a pH of 6.6 to 6.8 and the Desormeaux Bay had a pH of 6.8 to 7.2
the water columns measured on July 31, 2013. Even though these methods have proven effective, especially in
the southern US lakes, these methods could result in excessive costs for the low impact predicted for these
conditions for Lac St-Pierre.
HARVESTING
The method of mechanical cutting or harvesting in watermilfoil, large-leaved pondweed, and robinsii pondweed
beds could be promising for Lac St-Pierre when used in combination with hypolimnetic aeration. Cutting and
removing the upper part of the plant would produce immediate results and limit its spread through fragments
produced by the boat traffic. Lac St-Pierre is a busy place for vacationing and all kinds of water sports. However,
certain rules need to be followed to maximize achievement of short- and medium-term outcomes. First, the
harvesting must be done before installing the aeration system and not during the fish spawning periods—after
May (pike, yellow perch, and bass) and before September (trout and brook trout which spawn in the fall at
temperatures between 10°C and 12°C). The cutting should be performed during the watermilfoil’s flowering
Page49
period in order to weaken the plants for the following years. The flowering period is usually from mid-July to late
July. Access to the site for the mower must be well laid out and any risk of deterioration in the bank should be
avoided. Finally, a net or other system should be placed in order to recover all the fragments from cut plants.
Figure 34. Ice fishing on Lac St-Pierre. Source: Michel Francoeur
Page50
ENVIRONMENTAL IMPACTS
Environmentalimpacts
HUMAN AND SOCIOECONOMIC ENVIRONMENT
An aquatic plant invasion, as seen in Lac St-Pierre, negatively impacts the visual aspects of the environment as
well as swimming, sport fishing, and all types of boating. The spread of these aquatic plants reduces the value of
the lakeside properties and also the number of summer tourists and vacationers (including cottage, fishing, boat,
water ski, etc. rentals). It is clear that there is a direct relationship between the watermilfoil and the economic
benefits of the Val-des-Monts region, which is valued for its many beautiful lakes—especially during the summer
season.
Therefore, it is essential to take actions to reduce the spread of watermilfoil and invasive aquatic plants in order
to counter the above-mentioned negative effects. Goals regarding the human environment include raising the
quality of life for lakeside residents and the full utilization of the lake for recreational, touristic, and economic
purposes.
However, using a hypolimnetic aeration system, especially one powered by electricity, could become a source of
noise pollution. To minimize the noise, it is important to select a strategic location for the compressor cabinets
and ensure they are far away enough. To avoid any complaints about the noise, it is recommended to notify the
nearby residents and obtain their consent. It is also recommended limit boat access to untreated areas and areas
without aquatic plants (profundal zones only).
NATURAL ENVIRONMENT
It is very difficult to determine precisely the expected results from the hypolimnetic aeration in the short,
medium, and long terms. This is due to many factors which vary from lake to lake. However, the impact of anoxia
(lack of oxygen) at the bottom of the lake on the fish population could be reflected in a decrease in their number
in future years, especially for salmonids, if the situation continues to deteriorate. There are also signs of the
eutrophication of Lac St-Pierre, specifically with regard to the water phosphorus concentration in the last 14
years. All these effects, including the watermilfoil invasion problem, are important factors for the health and
ecology of the natural environment.
The hypolimnetic aeration is a method that is still being studied and it is used to counter hypolimnetic anoxia and
other associated problems. This method could increase the dissolved oxygen content of the hypolimnion and the
habitat and food supply of species of cold-water fish, and reduce the phosphorus cycling of sediments, thus
ensuring the oxygenation of the sediment-water interface.This could also reduce the production of ammonia
nitrogen, iron, and manganese. In theory, this method could help reduce cyanobacteria by stimulating the
growth of diatoms, which multiply with the artificial stirring of the water. However, more in-depth analysis (of the
dissolved organic carbon and phytoplankton sampling) is required to obtain reliable results. If the results do not
support the hypothesis, the reverse effect may occur (for example, if the surface water is nutrient-poor).
Increased monitoring, during the first and coming years, will help identify all the risks of releasing the sediments
and increasing the available nutrients in the water. This could also result in an increase in fish kills in the first year.
This is due to an increase in the muddiness of water, which could clog fish gills causing suffocation.
Page51
ENVIRONMENTAL IMPACTS
The “Notice with respect to the artificial aeration or circulation of lake water for the restoration of water quality”
(l’Avis concernant l’aération ou la circulation artificielle de l’eau des lacs comme mesures de restauration de la
qualité de l’eau du Ministère de l’Environnement du Québec), published in July 2003 by the Quebec Department
of Sustainable Development, Environment and the Fight against Climate Change, recommends holistic approach
based on a complete picture of the current lake situation.
Figure 35. A green frog. Source: Mélanie Renaud
Page52
OTHER RECOMMENDATIONS
Other recommendations
HOLISTIC APPROACH AND LAC ST-PIERRE ASSOCIATION EFFORTS
As recommended by the De Department of Sustainable Development, Environment and the Fight against Climate
Change, this study also advocates the holistic approach. It is important to take into consideration all the efforts
made by the Lac St-Pierre Association, a very proactive group of lakeside residents. These efforts include an
extensive awareness campaign through their website, regular information meetings, and annual general
assembly, which many lakeside residents, members of Federation of Lakes of Val-Des-Monts, and the mayor and
municipal councillors of Val-des-Months attend. Also, there is a pamphlet on good environmental practices such
as recreational boating; setting up a lake-monitoring committee; annual placing of buoys to identify the
watermilfoil zone boundaries; yearly water sampling to measure the phosphorus level; promoting awareness of
the use of fertilizers, compost, and pesticides on the lakeshore; continuously working with the Municipality of
Val-des-Monts on the public boat launching ramp (implementing the by-law banning wakeboard boats and
personal watercrafts); encouraging the lakeside residential development; and establishing a partnership with a
household product company that is ecological, does not use phosphates, etc.
MUNICIPALITY OF VAL-DES-MONTS
Other simultaneous measures can be adopted and implemented. This includes the septic pumping program by
Municipality of Val-des-Monts that was introduced in 2014. This program would require the regular inspection,
draining, and compliance of septic systems in the area and on all lakeside properties whether they used only in
the summer or year-round. Furthermore, introducing a by-law that requires lakeside residents to preserve at
least the first 5 metres of the shoreline around the entire lake (with a 5 metre opening for access to the lake for
each property) is fundamental for maintaining the protective belt which acts as a barrier against the lixiviation
and runoff of nutrients in the lake.
It is also strongly recommended to install a high-pressure boat wash station near the boat launching ramp and to
require a washing certificate for every boat that enters Lac St-Pierre.
In addition, lakeside erosion and consequently lake sediments can be minimized by introducing a by-law requiring
the speed of recreational boats used for water sports to be reduced less than 300 meters from the shore.
WATER QUALITY ANALYSIS
It is recommended that total phosphorus analysis, as implemented by the Lac St-Pierre Association, be continued
and that water transparency be measured twice a month throughout the summer. It is also recommended that
total phosphorus, dissolved organic carbon, and chlorophyll-a amounts be analyzed three times (in June, July, and
August) for the first two years and again after two years to re-evaluate the trophic status of the lake.
LAC MCMULLIN
Lac McMullin also falls within the purview of the Lac St-Pierre Association and is located upstream to the north of
Lac St-Pierre. The Eurasian watermilfoil invasion problem also affects Lac McMullin. In view of the above analysis,
Page 53
OTHER RECOMMENDATIONS
it is advisable to implement similar treatments and corrective measures to improve the water quality of the
tributary of Lac St-Pierre. This will reduce the flow of watermilfoil from Lac McMullin.
Figure 36. Large-leaved pondweed. Source: Mélanie Renaud
Page 54
REQUIRED APPROVALS
Required approvals
THE DEPARTMENT OF SUSTAINABLE DEVELOPMENT, ENVIRONMENT AND THE FIGHT AGAINST
CLIMATE CHANGE
•
A certificate of authorization from the Department of Sustainable Development, Environment and the Fight
against Climate Change is required prior to purchasing any device or system for controlling aquatic plants. To
obtain this certificate, the Lac St-Pierre Association must complete the certificate application form and pay
the fee (see Appendix 1). It is recommended to attach the current study to the application form to clearly
illustrate the Lac St-Pierre situation. The waiting period for a certificate of authorization is usually about 75
days. The fee for a certificate of authorization the certificate is around $553.
•
In addition, the application must be accompanied by a letter from the secretary-treasurer of the Municipality
of Val-des-Monts certifying that the proposed plans do not contravene any municipal by-laws.
Figure 37. Buoy on Lac St-Pierre. Source: Mélanie Renaud
Page 55
AVAILABLE RESOURCES
Available resources
PARTNERSHIPS AND FINANCIAL RESOURCES
The Municipality of Val-des-Monts
The Lac St-Pierre Association could explore the possibility of partnering with the Municipality of Val-des-Monts to
implement the project. In fact, several Quebec lakes have been financed by their municipalities to implement
systems that reduce aquatic plants. For example, lakes Lola and Gauvreau of the Municipality of La Pêche; lakes
Ludger and Cardin of the Municipality of Lantier; Lac Carré of the Municipality of St-Faustin-Le-Carré; etc. One of
the first steps in implementing the project may involve a meeting with the municipal councillors and the mayor.
The Federation of Lakes of Val-Des-Monts
The Federation of Lakes of Val-Des-Monts, a charitable organization, could be an attractive partner to request
funding from for this project. Even though financial conditions are becoming tighter and tighter, this avenue
should be explored. Also, the Lac St-Pierre Association could benefit from the Federation of Lakes of Val-DesMonts’ expertise in performing various analyses, completing tasks, and managing projects.
The ABV des 7 (Agency of 7 Watersheds)
The ABV des 7 also has solid expertise regarding lakes and problems with watermilfoil, as shown by their
experimental burlap project at Lac Pémichigan. This kind of organization could prove to be a great partnership
and could possibly lead student employment for technical work and field work.
Local businesses
Local businesses could contribute to the implementation and completion of the project with regard to material
and financial resources since they are the main recipients of the economic benefits generated by Lac St-Pierre
tourism. It is also possible to receive donations towards the completion of this project if a partnership with the
Federation of Lakes of Val-Des-Monts is established. These suggestions have to be approved by the respective
organizations.
Universities with environmental and/or biology departments
Depending on the project specifics, it would be worthwhile to approach universities in order to propose and offer
the possibility of student employment as part of their research and education programs.
Page 56
CONCLUSION
Conclusion
The Lac St-Pierre watermilfoil problem is the result of many factors, most of which were listed in this study. The
accelerated eutrophication of the lake is another major problem. There is no single solution, but the combination
of several simultaneous initiatives could not only help reduce and control the Eurasian watermilfoil and the
invasive aquatic plants but also improve the lake water quality and amenities. Lake eutrophication could be
delayed or even reversed by implementing all the recommendations and the holistic approach. With regard to
control methods, hypolimnetic aeration is considered the method of choice, but it could also be combined with
the mechanical method of cutting the plants. These methods are not a quick fix. They are to be used in
conjunction with good environmental practices from all lakeside residents and other users of the lake to improve
the water quality and ecology of Lac St-Pierre.
Figure 38. Lac St-Pierre. Source: Federation of Lakes 2013 Calendar, by Claude Mondoux
Page 57
REFERENCES AND BIBLIOGRAPHY
References and bibliography
Lac St-Pierre Association, 2009. www.lacstpierre.ca. http://www.lacstpierre.ca/water2/index.shtml
Conseil régional de l’environnement des Laurentides. 2013. CRE Laurentides .
http://www.crelaurentides.org/index.php/documents/eau-lacs
Conseil régional de l’environnement des Laurentides. 2013. Limnologie 101, eutrophisation et bonnes pratiques.
http://www.crelaurentides.org/images/images_site/documents/presentations/eutrophisation.pdf
Conseil régional de l’environnement des Laurentides. 2013. Les plantes aquatiques et les algues.
http://www.crelaurentides.org/images/images_site/documents/presentations/plantesaquaetalgues.pdf
Canadianpond.ca 2014. http://canadianpond.ca/
Weeds B’ Gone. http://www.weedsbgone.com/services/aeration-3/
CLEAN-FLO. http://www.clean-flo.com/
Lake Savers http://lake-savers.com/our-solution/revive/
Lake Champlain basin program.
http://www.lcbp.org/water-environment/aquatic-invasive-species/aquatic-invasive-species-spread/
Le lac Hotte, St-André d’Avellin 2014. http://www.lebulletin.net/Actualites/2013-11-07/article3471169/L%26rsquo%3BAssociation-des-proprietaires-du-lac-Hotte-en-guerre-contre-le-myriophylle-a-epi/1
RAPPEL. SOLUTIONS CURATIVES POUR LA RESTAURATION DE LACS PRÉSENTANT DES SIGNES D’EUTROPHISATION
http://www.rappel.qc.ca/IMG/pdf/OEDD_solutions_miracles.pdf
Association du lac Blue Sea. http://www.associationbluesea.org/
Municipalité St-Faustin le Carré. Lac Carré 2014.
http://www.municipalite.stfaustin.qc.ca/Documents/Environnement%20et%20Urbanisme/Rapport%20eutrophis
ation%20des%20lacs%202014.html/rapport%20%20eutrophisation%202009%202011%20%20lac%20carre.pdf
Page 58
CONTACT INFORMATION
Contact information
MÉLANIE RENAUD
ECOLOGY CONSULTANT
819-661-1332
[email protected]
____________________________________________________
Mélanie Renaud, Ecology Consultant
185 3e Rang du Gore Road
Lochaber QC
819-661-1332
[email protected]
Page 59
APPENDICES
Appendices
Page 60
APPENDICES
Certificate of authorization application:
http://www.mffp.gouv.qc.ca/faune/habitats-fauniques/pdf/demande-autorisation.pdf
Page 61

feasibility study reducing/removing eurasian watermilfoil

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