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Comments and Suggestions in Relation toPhosphorus Levelsin Lower Beverly Lakeby Earl Patric (2009) |
General
Freshwater lake contamination by the element phosphorus (P) is a very widespread and common problem in Canada and the United States. A 2007 report by Environment Canada called phosphorus “a national freshwater-quality issue” finding that one-third of southern Canada’s water monitoring sites exceeded the safety threshold for fish and other water life more than half the time. Dr. David Schindler is a leading water ecologist and researcher at the University of Alberta. He claims that hundreds of Canadian lakes are now burdened with excess levels of phosphorus, including the tenth largest freshwater lake in the world (Lake Winnipeg). The U.S. Environmental Protection Agency proclaims the element a widespread national problem, estimating that 50 to 60 percent of contamination is traceable to detergents.
Along with nitrogen and potassium, phosphorus is an element essential to plant growth. In freshwater lake bodies as little as three ppb (parts per billion) phosphate is sufficient to stimulate plant growth. As phosphate levels (and also nitrates) increase further, aquatic vegetation flourishes and may become a nuisance to water users. Accompanying the high nutrient levels are outbreaks of algae, a slimy and unattractive addition to the lake flora. While algae absorbs and uses phosphorus, it then dies off, releasing most of the phosphorus to the bottom. The decaying vegetation then absorbs oxygen from the water, jeopardizing the well-being of the aquatic animal life. The waters then await new inputs of phosphorus to start another algae cycle.
Lower Beverley Lake
Since heavy soils in Lower Beverley Lake’s extensive watershed (26,000 hectares) cause most of the one meter of annual rainfall to surface drain into the lake, there is potential for substantial lake contamination from surface runoff. In the case of phosphorus, though, lake contamination from overland sources may be quite limited, because soil quickly ties up phosphorus running off the surface. This is less likely true of nitrates. It is likely, therefore, that most phosphorus contamination of Lower Beverley Lake arises from direct inputs into the lake’s several creeks, plus the inputs into the lake itself.
To the writer’s knowledge there has not been an intensive and complete analysis of the lake’s main body or its numerous inlets. However, from 1999 to 2009 there have been extensive secchi disc readings in the lake and some in the vicinity of inlets (453 readings). During this same period there have been some determinations of total phosphates (149 readings) from the same sampling locations. The following paragraphs provide a brief overview of the observations. I have included only phosphorus readings since the year 2000, since earlier methodology involved higher error levels.
For the first decade of the 2000’s the mean total phosphate level for Lower Beverley Lake was 21.3 ppb. The standard deviation about the mean was 4.6. We can therefore make the statement that about two-thirds of all samples would likely fall between 16.7 ppb and 25.9 ppb. A standard deviation in much environmental data runs substantially over this, so I think we have a strong basis for confidence in the above.
Secchi disc readings are more variable and difficult to evaluate. Readings ranged from a low of 1.5 meters to a high of 4.6 meters. There does not appear to be a close correlation between secchi disc readings and total phosphate determinations. There are 20 readings over 3.0 meters, with the mean total phosphate level being 20.1. There are 20 readings measuring under 2.1 meters where the mean total phosphate level is 24.4 ppb. Thus, there is only a difference of 4.3 ppb total phosphates when taken from the extremes of secchi disc readings.
My only conclusion is that it is now well established that there are high levels of phosphates in the lake.
Sources of Lake Phosphorus
Because no water sampling has occurred in the streams leading into Lower Beverley Lake, we cannot at this time differentiate between watershed sources and direct sources on or in the lake itself. We can, however, make some informed guesses, and these follow in estimated order of importance:
1. Detergents – Detergents bearing phosphorus are likely to account for over half of phosphorus pollution. They may include dishwater, laundry, soap, and cleaning compounds. Powdered detergents typically contain more phosphorus than liquid detergents. Harsh cleaning agents such as washing soda (trisodium phosphate) would add heavily to the lake if in common use. In a typical house about 40% of water used drains into and through the shower and another 40% is flushed down the toilet.
2. Septic Systems – Eventually, most of the contents of all septic systems will at some point reach the lake. Poorly designed or faulty systems may provide immediate high phosphate input. There are roughly 400 households bordering Lower Beverley Lake, which has a perimeter of 44 km – perhaps one septic system per 110 meters. A typical septic system handles both gray water from showers, sinks, and tubs, and black water or human sewage. All metabolic animal waste possesses fairly high phosphorus levels. Dwellings on islands present a special problem, as they are frequently located on shallow soils above bedrock.
3. Oil Pollution – The LaMotte Company, a manufacturer of water analysis equipment, states that “some experts estimate that 40% of the pollution in America’s waterways is from used crankcase oil.” I suspect that this figure would be too high for Lower Beverley Lake. Phosphorus is always present in petroleum. Two-stroke boat engines employ a mix of lubricating oil and gasoline. The oil component must ultimately be discharged into the waters. Four-stroke engines are substantially less responsible for contamination by oil, as no oil is added to their fuel. Careless handling of waste oil and runoff from paved surfaces contribute to pollution from this source.
4. Agriculture – animal manure contains high nutrient levels including both phosphates and nitrates. Manure deposited on land is not likely to be a problem during the growing season, due to the soil tying up the nutrients, especially phosphorus. Manure spreads over frozen agricultural land and washing directly into creeks and the lake may be an important problem and should be investigated. Fertilizers spread on crops are not likely to be a problem, and it is unlikely that domestic gardens represent a problem. Where large animals like cows and horses stand in streams to avoid insects and heat, there is a problem. The writer has not seen many such situations, so the importance is unknown at this time.
5. . Lawns – Lawns which slope into the lake may occasionally be a problem when artificially fertilized. Where fertilizer contains phosphorus, there is a source of contamination. The writer is not familiar with cottage lawn fertilization practices, or, if used, whether phosphorus is present in significant quantities.
6. Island Cottages – Many such cottages now employ “chemical toilets.” These toilets treat the human sewage, but the resultant residues may find their way into the lake if carelessly handled. Gray water from island cottages is probably a problem.
7. Wildlife – High populations of wild animals contribute to nutrient levels of the lake.
8. . Feed Mill Discharges – Feed mill waste is a potential source of pollution, but nothing further is known by the writer. The Cataraqui Conservation Authority may have some insights here.
9. Whey – Historically, there were literally dozens of cheese factories within the 26,000 hectare watershed. They were almost always located along water courses to provide for the disposition of the by-product waste whey, a material with high phosphorus content. In the last decade only one factory produced whey, and they were authorized to spread the whey on agricultural land. Last year, this authority was withdrawn, and the last cheese factory was closed, concluding this important problem. The operation was on the outer edge of the watershed, and its recent threat to Lower Beverley Lake, if any, is not known.
Suggested Actions
1. Thinking only of Lower Beverley Lake, there does not seem to be much need to continue the present program of disc readings and total phosphate determinations. The program has determined about all that it can considering the design. Of course, if we are collaborating with other agencies, this suggestion may be premature. If we want to follow long term trends concerning phosphorus, I believe that we need to redesign the work, establishing a few fixed-location sampling points and a tighter regimen of sampling over time.
2. We may wish to undertake a short-term effort to clearly compare lake water samples with creek water samples. Such an effort would help to identify pollution sources. Before this is undertaken, a comprehensive effort should be made to learn what other agencies may already have done or are currently doing.
3. Assuming that we agree that phosphate pollution is an important problem, we need to share our concerns with lakeside owners and lake users. I doubt if many people are much aware of the problem. A sustained educational program could be helpful.
4. I think we should be careful about urging our members to use phosphorus-free detergents. The August, 2009 Consumer’s Report is not encouraging about their efficacy, and the cost of the one moderately effective detergent (“Method”) is high. If people still wish to use the phosphorus-free detergents that is certainly fine. Until really good phosphorus-free detergents are available, I think it might be well to emphasize efficient septic systems, managing the phosphorus and other environmental contaminants in the soil drainage fields.
5. We should support the Municipality’s septic system inspection program, and also support the enforcements of its findings.
6. We should applaud the current trend towards four-cycle outboard engines. No matter what the two-cycle engine sales personnel may say, these engines use oil mixed with gasoline, and the oil or its broken down components must end up in the lake.
7. We should investigate my concern that distribution of animal manure on frozen agricultural land may be an important source of lake contamination. The promotion of livestock fencing from streams is a useful activity.
8. I think that we should try to determine whether or not lawn fertilization is a common practice. If it is, we should encourage minimal phosphate component in these fertilizers.
9. There is a widespread notion that it is a bad practice for “blackwater” to enter the lake, but that it is okay to drain “graywater” into it. Blackwater does contain the added hazard of E. coli, but the graywater is likely to introduce the most phosphates. There needs to be education on this issue.
10. Finally, I think that the Lower Beverley Lake Association should step up its political activity. We attempt to effectively represent 200 members and 400 lakeside owners. We help to provide a safer and more rewarding lake environment for a much larger group of boaters, sports, tourists, nature buffs, writers, photographers, etc. This constitutes a potentially powerful force if it could be effectively marshaled and directed. We should invite candidates for local elected offices to meet the directors, to explain how their platforms contribute to collective LBLA interests. We should advise our members about candidates that we think would or would not be in our best interest to elect.