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| Collecting water to be tested |
The society has been taking samples from the Bevern, Plumpton Mill and Northend streams on a regular basis since May 2001. More recently sites on the Rivers Ouse and Uck along with many other tributaries have been included as well. Since 2005 some of the original sites that demonstrated no significant failure of acceptable water quality have been substituted but data recorded retained.
Samples from Sheffield Mill, some way
downstream from the Sloop will also be analysed. All these new sites
are on the section of the River Ouse that has now been designated
as a salmonid water (EU Freshwater Fisheries Directive).
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| Initial measurements of temperature & dissolved oxygen being taken before the water samples are sent away for full analysis. |
The intention is to provide evidence
that in some cases the water quality falls short of the standards that are laid
down in the EC Freshwater Fish Directive 78/659/EEC, even for cyprinid
(coarse) fish. For this purpose it is necessary to collect a minimum
of twelve samples and calculate an average. We would, of course, like
to see the status of the streams upgraded to salmonid standards, which
are more rigorous. The samples
also help identify
isolated cases of
pollution, which are reported to the Environment Agency for immediate
investigation.
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| Full analysis of water samples |
Already we can show that in the Bevern
stream the water quality deteriorates downstream from Ditchling, which
is close to the source. This is due in part to the quantity of treated
sewage discharged into the water, which is far too high for the current
flow rates, especially during drought conditions in the summer.
Each sample is tested for ammonia (usually
from
sewage effluent), phosphate (from sewage and to
a lesser extent from agricultural fertilisers) and dissolved oxygen
concentration. Our tests are carried out “in house” using
standard scientific test equipment suitable for measuring concentrations
of Ammonia (N), Phosphate (PO4) and dissolved Oxygen O2.The test results are published in our Monthly Water Quality Report as they become available.
In Sepember 2007 we started testing Nitrate levels. Nitrates are present in sewage effluents and agricultural fertilisers. Their presence in significant amounts causes eutrophication and there are perceived health hazards from their presence in drinking water. In many areas of the UK high amounts of nitrate in ground water has caused concern and there are now designated Nitrate Vulnerable Zones where use of nitrate fertilisers is restricted. We measure the amount of nitrogen derived from the nitrates in our samples (NO3 as N). The EU Freshwater Fisheries Directive does not set parameters for nitrates, but for nitrites (N02) it gives guide values which are shown in the second table below.
S.O.C.S. designated acceptable limit values
| Ammonia |
< 0.4 mg/l N |
| Phosphate |
< 4 mg/l PO4 |
| Nitrate |
< 5mg/l NO3 |
| Dissolved Oxygen |
> 3 mg/l O2 |
The levels set out in the table on the right are S.O.C.S. designated acceptable limit values.
These levels have been arbitrarily
chosen to reflect what can reasonably be expected in these waters
although they are less stringent than the guide values laid down in the
directive. These guide values can be found in the table below.
EU Freshwater Fisheries Directive Guide values
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Salmonid |
Cyprinid |
| Ammonia (as N) |
< 0.03 mg/l |
< 0.16mg/l |
| Phosphate |
< 0.2 mg/l |
< 0.4mg/l |
| Nitrate |
< 0.01 mg/l |
< 0.03 mg/l |
| Dissolved Oxygen |
50% saturation > 9mg/l
100% saturation > 7mg/l
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50% saturation > 8mg/l
100% saturation > 7 mg/l |
The dissolved oxygen in pure chalk spring water can vary from 12 mg/litre
at 5 degrees centigrade to 8 mg/litre at 25 degrees. The amount of dissolved oxygen present depends upon the temperature. Organic matter (pollution) can consume some oxygen and the water is then partially saturated. The minimum acceptable concentration is 4 mg/litre. Water with 4 mg/litre at 25 degrees would be 50 %saturated (4/8 x100). The percentage saturation is therefore a measure of pollution. Most samples we test are between 50 to 70 % saturated.
EU Freshwater Fisheries Directive Mandatory values
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Salmonid |
Cyprinid |
| Ammonia (as N) |
< 0.78 mg/l |
< 0.78mg/l |
| Dissolved Oxygen |
50% saturation > 9mg/l
100% saturation > 6mg/l
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50% saturation > 7mg/l
100% saturation > 4mg/l |
| Phosphate |
No
mandatory limit
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No mandatory limit |
The Freshwater Fisheries Directive also lays down mandatory parameters for dissolved oxygen and ammonia. These are shown in the table on the right.
Note:
There is no mandatory limit laid down for the phosphate or Nitrate levels in lotic waters. |
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