| e g drinking blue-greens Proportional sources of phosphorus in St. Mary and Cusheon Lake, Saltspring Island, BC |
Diana Lynn Thompson Home Gallery Recent projects 2000-2002 1994 -99 Exhibition List CV Site Map News/ Updates Contact |
| art about cyanobacteria Saltspring island drinking water installation art cyanobacteria in St. Mary lake Cusheon Lake blue-green algae Salt Spring Island BC |
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John Sprague PhD, gave me the following information in early September 2007. ” …regeneration from the bottom sediments is by far the biggest annual source of P to the water [of St. Mary Lake]. Using data from a thorough study in the early 1980s, I have estimated the proportional sources as follows: Regeneration 65% Septic fields 30% Land via creeks 4% Groundwater input 1% Rainfall 0.2% Those numbers are probably still relevant. If anything, I would think that regeneration has increased its contribution since then. I intend to review recent data and give a more recent estimate of sources, later this autumn. Unless the regeneration is beaten (aeration), there is no hope of getting the lake into a recovered state.” "…in September of 1999, Cusheon Lake had a more serious problem of cyanobacteria… There was a ban for several weeks on using its water for drinking, washing, or bathing. You might be interested that the sources of P for Cusheon Lake are rather different: " Land runoff 53% Residences, septic 24% Regeneration 22% Rainfall 2% Dr. Sprague gave me his sources as well: "For my estimate of St. Mary Lake, I used the numbers of Dr. Rick Nordin and colleagues, from their 1983 report. The estimate for Cusheon Lake is based on about a person-year of my time and of some other volunteers, doing some monitoring and modelling. The numbers are pretty firm, i.e. the general proportions are likely to be quite close to the numbers I gave you. I have a report on that which will soon be in electronic form if all goes well, and easily available." ... you may quote the numbers. Please do. The more people know what is going on, the better." |
| "Drinking blue-greens" installation August 2007 |
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| "Drinking blue-greens" three-hour installation on St. Mary Lake September 2007 |