I live on a small freshwater "pond" in eastern Ontario and have
measured the water quality 3 times in two years with the following
results.

             E-Coli     N-NH3           N-NO3    Total-P
June 2001    5 ct/100mL <0.2 mg/L       1.35     0.02
July 2001    2          0.03            <0.10    0.01 
June 2002    17         <0.2            <0.10    <0.01

My questions are...

* How is this lake doing as your basic "swimming hole" - is it in good
shape - are there any trends that I should be worried about here?

* Am I measuring the correct items?

* Are there specific levels of items I should watch closely - for
example what if e.coli becomes greater than 100?

FYI - The pond is man made, about 22 acres, is spring fed and is in
sand

Hello,

This is a good question. The "Water Impacts" Quality site

   http://www.ae.iastate.edu/Ae573_ast475/Water_Impacts_Notes.htm

suggests that total ammonia (NH3 + NH4) concentration should be
between 160mg/L at pH of 6.0 and 0.06 mg/L at pH 9.0. Assuming your
measurements include both NH3 and NH4, it seems that these readings
are safe. If your testing apparatus only measures NH3 however, the .2
mg/L reading is dangerously high. The site above should clarify this
matter.

As far as nitrates (NO3) are concerned, you have little to worry
about. Dangerous levels of nitrates occur at concentrations of 10mg/L
for humans, which is many times higher than your measurements.

Your Phosphorus levels are right on target. The EPA categorizes
phosphorus levels of .01 to .03 mg/L (or 10-30 micrograms/L) as being
good for "uncontaminated lakes". Your measurements are within these
guidelines.

In testing for e-coli, a safe range is 130 bacteria per 100
milliliters of water. Your current measurements are well under this
level, but the site advises that a total of five tests should be taken
over 30 days and the results averaged. I got this from :

   http://health.co.genesee.mi.us/A-Z/is_the_lake_safe_to_swim_in.htm

If levels become dangerous, I would suggest calling your local health
department to explore corrective measures.

In conclusion:

>From your measurements, it seems as if your swimming hole is doing
well! Again, I would make sure that your NH3 test is accurate, but
overall, it looks good.

It appears that you are measuring the right items- they are the only
ones listed as "quality factors". An explanation of the
importance/impacts of the concentration of these substances is
available at the websites provided.

Thanks for the question!

-- ukiguy