A remarkable degree of chemical variation in the Old Pond

The Old Pond yesterday showing water conductivity values (and rather more Lemna than I'd expected this pond to have!)

One of the special things about ponds is how much they differ from place to place.

And the Old Pond is providing an excellent example of this phenomenon at the moment in its water quality.

Because the three basins of the pond – which have now been separate for about two months as a result of the dry weather – are showing big difference in water conductivity, considering how close they are to each other and that they have been supplied with exactly the same water throughout.

Yesterday the front small pool had a conductivity of 232 – that’s quite high, at the top end of what I’d expect to be unpolluted’; the middle right shaded pool was at 162 – a good low value; and the back Typha pool was a very low 53.

I was very surprised by the differences in the three ponds.

Conductivity is a very useful measure (and cheap) but it can’t tell you which dissolved chemicals are contributing to the overall score. To find that out you need a much more time consuming / expensive laboratory analysis.

So I don’t know what’s causing these differences.

But two things are interesting:

– the back Typha pool, which still has rich growths of moss – is cleaner than rainwater.

– designing the pond to have basins that separated when the water levels went down in summer was intended to create diversity in physical and chemical conditions.

At the moment it certainly seems to be working.


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