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Lake Restoration, the Canadian experience
Summary of in-lake methodology for both culturally and naturally eutrophic lakes
Soil & Water Conservation Society of Metro Halifax (SWCSMH)
Updated: Septewmber 19, 2013
"The lakes we remember once drew us to swim, to picnic, to
canoe. We found in them beauty, mystery, and tranquillity.
Lakes continue to inspire our daily lives, while at the same time
providing transportation, an abundant food supply, and water for
drinking and bathing. By serving as a critical link in the
ecosystem, lakes also are important sanctuaries for our fish and
wildlife. But for some of us, the lakes of our childhood- and of
our nation's economic strength- are rapidly changing. While we
all share responsibility for the cause, we also share
responsibility for restoring our deteriorating lakes to their
former beauty". ............ Anon
Several procedures to reduce the level of nutrients within lakes without
changing loading rates have been devised (see our Synopsis titled "Lake
Restoration/Management", Feb. 93). Dredging may be appropriate for lakes
whose sediments are high in nutrients. Chemical precipitation is
possible. Dilution or flushing is possible if large quantities of low
nutrient water are available. Harvesting of both algae and macrophytes
can remove nutrients. Lake sediments can be sealed to prevent nutrient
release. Artificial aeration techniques can be used to improve water
quality, and provide suitable cold water habitat during periods of
The different pathways of phosphorus and nitrogen in lake metabolism make
phosphorus the obvious choice for eutrophication control. A certain
reduction of phosphorus input will generally result in a greater reduction
in algal biomass compared with the same reduction of nitrogen.
Furthermore, the reduction of nitrogen input without a proportional
reduction in phosphorus, creates low N/P ratio which favors nitrogen
fixing nuisance algae, without any reduction in algal biomass.
(1) While lime treatment has been extensively used to mitigate
acidification effects, several studies of calcium carbonate precipitation
led to the hypothesis that the addition of lime to lakes can also reduce
eutrophication. Lime has been added to several lakes and dugouts in
Western Canada (Frisken, Figure Eight, Andorra, Beaumaris, Valencia,
Halfmoon, Gour, Monnette, Desrosier, Frey, Fedora, Pederson, Sullivan,
Schreger, Limno) to improve water quality. These hardwater lakes are
eutrophic due to high natural, agricultural, or urban loadings of
phosphorus. Source control of phosphorus loadings would be extremely
difficult at all sites. Most of the lakes are primarily used for
recreation but the dugouts have been used for human and agricultural water
supplies. In two of the study sites, Figure Eight Lake and Frisken Lake,
most of the sediment iron is converted into pyrite. These lakes have
little reactive iron and presumably phosphorus biogeochemistry is not
controlled by iron reactions.
(2) The usual method for algal control is application of copper sulfate or
alum. But copper sulfate is toxic to nontarget organisms, and its use can
upset the ecostructure of lakes. The long term adverse effect of alum in
the natural environment is unknown. Proper application of lime
(specifically calcium hydroxide) reduces chlorophyll a levels. Calcium
hydroxide dissociates and forms calcium carbonate per
Ca(OH)2 + CO2 --> CaCO3 + H2O
These newly formed calcite crystals are small and present a relatively
large surface area for adsorption. Associated with phosphate adsorption
onto calcite is the molecular exchange of CO3-2 and PO4-3 on the surface
of growing calcite crystals as follows;
3CO3 - 2(S) + 2PO4 - 3(L) <--> 3CO3 - 2(L)+ 2PO4 - 3(S)
where S and L denote calcite and aqueous phases, respectively.
(3) Although biological reactions must influence phosphorus
biogeochemistry, the effect of lime treatment on phosphorus
biogeochemistry can be easily explained via apatite for mation. The
generally accepted model for apatite formation is that phosphorus
initially adsorbs to calcite and then a surface rearrangement produces
phosphate heteronuclei that ultimately form the stable mineral apatite.
If the surface application of calcium hydroxide was repeated for a number
of years, the titration should exceed an end point, phosphorus and calcium
should not redissolve, and phosphorus could be converted into apatite.
The optimal method of enhancing calcite and apatite formation in lakes is
not obvious, but several recommendations are possible. Lakes with rapid
hydraulic flushing or high and continuous nutrient loading are less
appropriate for lime treatment; however, lakes with a high short-term
spring loading of nutrients respond well to lime treatment. In lakes
without fish, a large dose of Ca(OH)2
should be used. In lakes with valuable fisheries, alternative
approaches to enhance apatite formation could include hypolimnetic
injection of Ca(OH)2 or larger surface applications of CaCO3.
(1) The applicability of aeration techniques to improve water quality is
briefly discussed below.
- Long-term studies are required to develop simple lake treatment
protocols and resolve important uncertainties. Although there is limited
long-term data, Figure Eight Lake results indicate that sequential
treatments result in suppression of sediment phosphorus release.
(2) Many deep lakes situated in the prairie
provinces are eutrophic. In May, 1988, a system was installed to inject
pure oxygen into the bottom of the hypolimnium of the north basin of Amisk
Lake (mean depth= 14.4 m). The south basin was not treated and served,
along with 7 yrs of background data, as the control. During summer 1988
(Prepas et al, 1990), the hypolimnetic oxygen depletion and TP
accumulation rates in the treated basin were only 42.5 % of historic
averages; during winter 1988-89, under-ice DO concs. were maintained at 5
mg/l. In contrast, the rates in the untreated south basin remained near
or above pretreatment rates.
- Domestic Water Supply: Aeration
can greatly reduce undesirable concentra tions of iron, manganese,
hydrogen sulfide, carbon dioxide, ammonia and other substances associated
with anaerobic conditions.
- Downstream Water Releases: Many
reservoir tailwaters contain valuable cold water fisheries. These
fisheries generally require water temperatures of less than 22oC and oxygen concentrations of 5 mg/l or more. Solutions include aeration/oxygenation of the hypolimnium.
- Industrial Uses: Some industrial
processes require cold noncorrosive and nonscaling water for cooling and
other purposes. This can be achieved by hypolimnetic
- Fisheries Management: Thermal
stratification and its associated hypolimnetic oxygen depletion in
eutrophic lakes is widely known to restrict fish and other biota to
shallow depths. In some cases the fish may be further compressed by warm
water above into a narrow band in the thermocline. At some time during
the summer there may be no place in the lake with suitable living
conditions for cold-water fish. Even if thermal and chemical
stratification are not lethal to the fish, they can severely stress the
population (Johnson, 1966; Mayhew, 1963). Hypolimnetic
aeration/oxygenation if properly used will create both suitable oxygen and
temperature conditions for coldwater fish.
- Algal Production: Algal biomass,
species composition, and rates of production can all be affected by
(3) Experimental aeration systems have been
installed in three British Columbia lakes (Ashley, 1988; Ashley et al,
1987). The lakes were Black (naturally eutrophic, surface area= 4.0 ha,
mean depth= 4.5 m), Glen (culturally eutrophic, surface area= 16.0 ha,
mean depth= 7.2 m), and St. Mary (culturally eutrophic, surface area= 182
ha, mean depth= 9.1 m). Full scale systems were installed in the last two
lakes, and the results were promising.
- Ashley, K.I. 1988. Hypolimnetic aeration research in British
Columbia. In Verh. Internat. Verein. Limnol. 23:215-219.
- Ashley, K.I., K.J. Hall, and D.S. Mavinic. 1991. Factors influencing
oxygen transfer in fine pore diffused aeration. In Wat. Res.
- Ashley, K.I., D.S. Mavinic, and K.J. Hall. 1990. Oxygen transfer in
full lift hypolimnetic aeration systems. Air-Water Mass Transfer, Second
International Symposium, U.S. Army Waterways Experiment Station/ASCE,
Sept. 11-14, 1990. 648-659.
- Ashley, K.I., S. Hay, and G.H. Scholten. 1987. Hypolimnetic aeration:
Field test of the empirical sizing method. In Wat. Res. 21(2):223-227.
- Ashley, K.I. 1985. Hypolimnetic aeration: Practical design and
application. In Water. Res. 19(6):735-740.
- Ashley, K.I., D.S. Mavinic, and K.J. Hall. 1990. Effects of orifice
size and surface conditions on oxygen transfer in a bench scale diffused
aeration system. In Environmental Technology. 11:609-618.
- Babin, J., E.E. Prepas, T.P. Murphy, and H.R. Hamilton. 1989. A test
of the effects of lime on algal biomass and total phosphorus on
concentrations in Edmonton stormwater retention lakes. In Lake and
Reserv. Manage. 5(1):129-135.
- Fast, A.W., and M.W. Lorenzen. 1976. Synoptic Survey of Hypolimnetic
Aeration. In J. Env. Engg. Div., ASCE. 102(EE6):1161-1173.
- Fast, A.W., M.W. Lorenzen, and J.H. Glenn. 1976. Comparative Study
with Costs of Hypolimnetic Aeration. In J. Env. Engg. Div., ASCE.
- Hanson, M.J., and H.G. Stefan. 1984. Side effects of 58 years of
copper sulphate treatment of the Fairmont Lakes, Minnesota. In Water.
Res. Bull. 20:889-900.
- Johnson, R.C. 1966. The effects of artificial circulation on
production in a thermally stratified lake. Wash. Dept. Fish., Fish. Res.
- Kortmann, R.W. 1989. Aeration Technologies and Sizing Methods. In
Lake Line, N. Am. Lake Manage. Soc., January 1989:6-7, 18-19.
- Lorenzen, M., and A. Fast. 1977. A Guide To Aeration/Circulation
Techniques For Lake Management. Corvallis Environmental Research Lab,
Oregon, U.S.E.P.A. EPA- 600/3-77-004. 125p.
- Mayhew, J. 1963. Thermal stratification and its effects on fish and
fishing in Red Haw Lake, Iowa. Biol. Sec., State Cons. Comm. 24pp.
- Murphy, T.P., E.E. Prepas, J.T. Lim, J.M. Crosby, and D.T. Walty.
1990. Evaluation of calcium carbonate and calcium hydroxide treatments of
prairie drinking water dugouts. In Lake and Reserv. Manage.
- Murphy, T.P., and E.E. Prepas. 1990. Lime treatment of hardwater
lakes to reduce eutrophication. In Verh. Internat. Verein. Limnol.
- Murphy, T.P., K.G. Hall, and T.G. Northcote. 1988. Lime treatment of
a hardwater lake to reduce eutrophication. In Lake and Reserv. Manage.
- Murphy, T.P., E. Prepas, and J. Babin. 1991. Limnology of Figure
Eight Lake in 1988. Effects of 1986 and 1987 lime treatments on water
quality. National Water Research Institute Report No. 91-13. 52p.
- Organization For Economic Co-Operation And Development (OECD). 1982.
Eutrophication Of Waters. Monitoring, Assessment And Control. 156pp.
- Prepas, E.E., T.P. Murphy, J.M. Babin, and J.T. Lim. 1990. Farm water
dugouts. A manual on the use of lime to provide good water quality.
National Water Research Institute Report No. 90-16. 8p.
- Prepas, E.E., T.P. Murphy, J.M. Crosby, D.T. Walty, J.T. Lim, J.
Babin, and P.A. Chambers. 1990. Reduction of phosphorus and chlorophyll
a concentrations following CaCO3 and Ca(OH)2 additions to hypereutrophic
Figure Eight Lake, Alberta. In Environ. Sci. Technol. 24(8):1252-1258.
- Prepas, E.E., D.J. Webb, C.L.K. Robinson, and T.P. Murphy. 1990.
Impact of liquid oxygen injection on a deep, naturally eutrophic, lake:
Amisk Lake, Alberta, year one. In Verh. Internat. Verein. Limnol. 24:320.
- Schindler, D.W. 1987. Detecting ecosystem responses to anthropogenic
stress. In Can. J. Fish Aquat. Sci. 44(suppl.1):6-25.
- Soil & Water Conservation Society of Metro Halifax. 1993. Synopsis titled "Lake Restoration/Management", 17p.
- Watt, W.D. 1986. The case for liming some Nova Scotia salmon rivers.
In Water, Air, and Soil Pollution. 31:775-789.
- White, W.J., W.D. Watt, and C.D. Scott. 1984. An experiment on the
feasibility of rehabilitating acidified atlantic salmon habitat in Nova
Scotia by the addition of lime. In Fisheries. 9(1):25-30.
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