Volunteering

The monthly monitoring we are carrying out along the Pillhill Brook would not be possible without our team of enthusiastic volunteers and site supervisors. We are always on the look out for individuals who are keen to expand their knowledge of chalk streams and have a few hours a month to get involved.

Training and support is currently funded by the Watercress & Winterbournes but you do not need to be trained to get involved. The best way to find out what we get up to is to come along to a monitoring session. The table below shows where and when will will be out carry out our monthly monitoring.

PBA Monitoring Schedule.pdf

Kick-sampling is a method of estimating the abundance of invertebrate species in a specific section of a river and by doing so take a measure of the health of the watercourse. We look specifically for 8 key species of invertebrate, sensitive to different water qualities. By dividing the river section into different habitats i.e. fast flow over open gravel versus slow flow through river plants, the aim is to catch a good cross-section of aquatic life. The method was created by the Riverfly Partnership and now estimated counts are sent to national database called Cartographer overseen by the Environmental Agency.

It is great fun building up knowledge on how invertebrates behave and it is fascinating to see how different habitats affect what we find. Habitat changes as brook depth and flow change with the seasons and this impacts the variety and abundance of invertebrate life we can expect to find. We have to know what to expect when the brook is unpolluted if we are to identify when something isn't right.

Collecting using a net

Volunteers are trained on how to carry out our kick-samples. It is every volunteer's aspiration to net as many invertebrates as possible but not bring too much of the plants, gravels and silts that they live in along too! Too much debris can make spotting and estimating counts challenging.

3 minute survey

Every month we reassess each survey site to see if the habitat has changed i.e. how flow has been affected by the growth of marginal and in channel plants and how much gravel can been seen. Different invertebrate species thrive in different habitats so the greater variety of habitat we find the greater variety of species we should find. So we divide our survey into 12 x 15 second kick-samples in as many different habitats as available to catch as many different species of invertebrate as possible. This will indicate how healthy the brook is at this location.

Counting

It's not possible to count every creature in our samples instead we look for the unusual first and then do an estimated count of the 8 key species we monitor. Each of these species are sensitive to different potential pollutants so if one were to disappear that may be a clue that something isn't right. This could lead to a site visit from the Environmental Agency.

Sampling tray

We put a species identifier mat under a segmented sampling tray to help with identification. Each species is quite different in either appearance or the way it moves so after some practice it is relatively easy to identify them. Some are quite small so a magnifying glass is always helpful.

Finding our iconic chalk stream mayfly always causes excitement and as stoneflies are a good indicator of clean, unpolluted water we are always pleased to find these too.

And of course we find other species that we unfortunately don't count such as demoiselles and dragonfly nymphs but that doesn't detract from the pleasure in finding them.

Mayfly nymph

Stonefly nymph

Dragonfly nymph

Demoiselle nymph

Water Quality Testing

Alongside our kick-sampling we test for phosphate, nitrate and ammonia and can get an immediate feel for the health of the brook. The testing kits come in a striking yellow box designed by the Angling Trust. As part of their Water Quality Monitoring Network the PBA submits monthly results to a national open access database where the water quality of a growing number of British rivers can be checked.

What's in the box?

Phosphate (green) and ammonia (yellow) meters plus nitrate test strips and a combined conductivity and temperature meter.

Phosphate testing

We test for the presence of phosphate and ammonia in similar ways. Using meters that measure the difference in the amount of light that can pass through a glass vial we first test pure brook water and then add a reagent that will 'stick' to phosphate particles. We then reinsert the vial into the meter and any light reduction caused by the presence of phosphate will be detected in parts per million (ppm).

Nitrate strips

Dipping a test strip into brook water for 1 second then waiting 30 seconds to see how the strip changes colour indicates the concentration (ppm) of nitrate present.

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If you would like to get involved please email us at pillhillbrook@gmail.com.

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