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drinking blue-greens




Proportional sources of phosphorus
in St. Mary and Cusheon Lake,
Saltspring Island, BC







     Diana Lynn
     Thompson





      
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art about cyanobacteria Saltspring island  drinking water  installation art
cyanobacteria in St. Mary lake  Cusheon Lake  blue-green algae Salt Spring Island BC
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
< drinking blue-greens
"Drinking blue-greens"  three-hour installation on St. Mary Lake September 2007
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