Harrow's Streams: Surveying and monitoring

Our Hanna Checkers provide accurate measurments of common pollutants

The Harrow's Streams project has bought six hand-held Hanna Checker colourimeters that allow us to test water for phosphate and ammonia. High phosphate levels are a clear sign of pollution from washing machines and dishwashers, while ammonia comes from human waste.

A second way of assessing the health of streams is by looking at the small animals ‐ invertebrates ‐ that live in the stream. If we find only a small number of pollution‐tolerant species then the stream is in poor health. Finding lots of species, some of which require clean water, shows that the stream is healthy. This “Riverfly Monitoring” approach has the advantage that it reveals intermittent problems ‐ if a misconnection releases foul water into a stream only once a week, it will still kill the invertebrates that require clean water, so when the Riverfly Monitoring sampling is done it will reaveal that the stream is unhealthy even if ammonia and phosphate levels are low at the time of testing.

Teams of volunteers are already riverfly monitoring at two places on the Yeading Brook West and at one place on the Yeading Brook East. However we need volunteers to monitor on the Edgware Brook and on the River Pinn. We have the necessary equipment to give out, we just need volunteers!

Become a Riverfly Monitor

The information collected by volunteer riverfly monitors reveals the health of Harrow's streams and rivers. It identifies points where pollution is high, so that officials can look for the sources of pollution upstream. It reveals when the health of a stream improves, either as the result of reduced pollution or because of physical changes in the stream such as rewilding or the creation of reed beds and settling pools.

It is also fun ‐ volunteers get to see and identify the different types of invertebrates found in their streams.

Volunteers are trained by experts and then monitor a specific patch of stream, recording the different invertebrates that they find and using this to score the health of the stream. Tests are done once a month, each test taking about an hour. We will try and set up teams of two or three volunteers at each specific point so that an individual volunteer tests every two or three months. Contact admin@harrowncf.org to discuss possibilities ‐ no obligation implied!

More advanced training

We have funds to send volunteers keen on further training on a Freshwater Biological Association residential course to learn more advanced identification skills.

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