Water Quality Report



Pond Conservation Supporter Advice



For Philippa Lausen, Winkleigh Pond Group, Devon,

– Water Quality Report December 2010



Information received:

"I am writing to you to find out whether you might be able to give our emerging biodiversity group some advice. We live in a small village in north Devon and are part of the North Devon biosphere Reserve. We are keen to form a group to carry out biodiversity related projects, and the first one we would like to tackle is a survey of the state of our ponds."

Note Big Pond Dip done for 22 sites, all labelled Winkleigh, Devon, Philippa Lausen.


Results

Water conductivity readings:
Measuring conductivity (in micro Siemens) is a useful and reliable test which measures the total quantity of chemicals dissolved in the water: both natural substances (e.g. calcium) and undesirable substances (e.g. too many nutrients). This makes conductivity a relatively cheap and quick test, which is why we use it so much, but it doesn’t tell you exactly what proportion of each chemical is in the water. We can make assumptions from our experience, but to be completely certain about the level of each pollutant you need to do laboratory tests. However, these cost considerably more money (we’re talking around £100+).

To give a bit of background on interpreting conductivity: rainwater normally has a reading of around 50-100 in central southern England, and unpolluted ponds are usually below about 300. Out of interest, tap water is usually 500-600 in the south of England, but is often lower in the north, or other places like west Wales, where water drains from moors, mountains or heathland. So we tell people to aim for a magic figure of 100 or less. Where conductivity is 500-1000+ µS/cm this is usually a sign of some kind of pollution.

There is a slight complication in the parts of the country with hard rocks and little calcium, like your area – where lower conductivity values can still be associated with pollution – there is a bit of expert judgement involved here!


Conclusions

I have expanded the original table with your new data– so you can see the conductivity against the BPD score and the creatures present.



Wendy’s new pond, which we presume is filled with rainwater, still has the lowest conductivity. For the other ponds, the conductivity readings of around 200 µS/cm would suggest a mixture of tapwater, diluted with rainwater, which is fairly usual for garden ponds, or rainwater with some build up of nutrient rich sediments.

Of the new ponds Maggie’s wildlife pond (we think, it is referred to as Maggie’s big pond in the BPD – so could this be the woodland pond?) is excellent, with a creature score of 43, and all the top invertebrates including caddis and alderfly larvae. Similarly Marian’s leat pond was also very good for biodiversity with a creature score of 42 and alderfly larvae, which are an indicator of clean water.

It would be good to find out more about these two ponds – location, profile, and particularly planting, since we think that the two most important factors are, clean water, and plant structure.

Maureen’s fish pond is interesting, as the conductivity was relatively low, but it appeared to have few creatures. However, given that it is a fish pond, it is possible that the fish have predated many of the creatures, or they were well hidden, so weren’t collected as easily. A similar pattern emerges with Maggie’s fish pond and Marian’s lake – which also had very low creature scores, despite reasonably moderate conductivity scores, implying fish predation is critical.

We should add that none of your conductivity readings are high – we regard anything below 500 as not too polluted, so you have a nice set of clean water ponds.