Our first results are here and the good news is we sit in the excellent (top 5%)
Coliform levels were in the excellent range at test point 2 (1 week ago) we tend to get results 7 days later so we should expect results 2 early next week. We specifically tested either side of an extreme rain event which should show us if these cause specific plumes of coliforms that swimmers/water users should be aware of.
Phosphate levels: at test point 2 – 1.5ppm phosphate level is a serious concern, on average it is around 0.8 is significant and is likely the cause of the algal blooms we see on the surface together with the longer term degradation of the waterway, we should explore the likely causes of these levels as results further up stream and downstream are better –
This is likely caused by the low flow of the water because of the weir, over the years that has built up a phosphate rich silt at the bottom of the river bed which is then released in warm weather just when flows are low amplifying the effects.
Nitrate levels of 10ppm (although normal for low land rivers) is still considered polluted though less of a worry than the Phosphate.
Drinking water comparison for human health:
For human drinking water, the regulatory limit is typically:
50 mg/L nitrate (as NO₃⁻) in the UK and EU
So 10 mg/L is well below drinking-water legal limits
Overall interpretation of nitrate levels to date:
the river is experiencing moderate nutrient enrichment which could be from agricultural or sewage inputs which could contribute to ecological degradation over time but it is not an extreme emergency level by itself.
Generally at test point 2 (lab test 1) it was excellent water quality for human health and above average in terms of
Overall
The river is healthy for human usage at test date 2.
However it is not a healthy river from an ecological perspective:
Nitrate levels are standard but still elevated over a natural level but an average phosphate level of 0.8 mg/L would generally be expected to:
- reduce ecological quality over time
- favor algae and nutrient-tolerant species
- stress sensitive aquatic life
- increase risk of oxygen problems and summer blooms
It is elevated enough that river scientists and regulators would usually regard it as a significant water-quality concern rather than a minor fluctuation.
Click on the Spreadsheet image to open the actual spreadsheet. (it’s a bit small to read here!)
