Water Quality

In addition to chemical checks, the presence/absence and abundance of certain freshwater invertebrates (often called macroinvertebrates) – the aquatic larval stage of various insects - can tell a story of a water body’s health. Because some invertebrates are more sensitive to pollutants than others, we can use them as “indicator species”.
Assessing the types of invertebrates found indicates something about the health of the water body they have been found in. For example worms can tolerate high levels of pollutants but some mayflies don’t tolerate even low levels of pollution. They also help describe when pollution events occur because some populations take a while to recover if they have been harmed by pollution.
The Trust is working with Frensham Fly Fishers who have a long-established routine of regular sampling, and a number of other groups along the river, combining findings and understanding how and where the river environment and water quality is being impacted. This supports the Riversearch Wardening scheme run by the Surrey Wildlife Trust, and our data are shared with Freshwater Watch, Water Rangers, and academic projects.

Chemical and ecological RiverFly test results are shown on this page. The Trust with other groups is supporting a Community Lab to provide access to more complex tests, and bacterial sampling results for e.coli and total coliforms are shown here and can also be found on the Water Rangers pages

Chemical Testing

Using Water Rangers test kits, the Trust works with other groups and organisations along the river to monitor quality using chemical testing and ecology sampling - the most recent reports are shown here. Click on the 'tap' symbol for details of that location.
Further details of the Southern Wey data are given on the River Wey group page:
Note that wider screen formats allow easier comparison across the sample sessions.

Invertebrate Sampling

Invertebrate (River Fly) samples showing a rolling 13 sets of results.

Observation Scoring
The Riverfly Project expected Target is an overall 7 for the water body.
Count estimate Rank Quality Score Value
1-9 A 1
10-99 B 2
100-999 C 3
> 1000 D 4

Water Quality Results

The River Wey Trust: F