Health of the River Piddle

Riverfly Monitoring- what is it?

The Dorset Wildlife Trust runs a River Monitoring Scheme, which is part of a national initiative. The scheme is of interest to keen anglers and wildlife enthusiasts alike, who both share a concern for the present and future health of our rivers.

The River Monitoring Scheme is based on the counting at regular intervals of key river insect species and other invertebrate groups as a method of assessing river quality. Many insect and invertebrate species are extremely sensitive to pollution levels and therefore their numbers act as an early warning system of any potential problems.

The methodology used is that of the Riverfly Partnership (www.riverflies.org). The number of 8 different groups of river insects and other invertebrates are counted through a 3 minute kick sample . Monitors are asked to carry out the surveys on a monthly basis between April and September, ideally at the same time each month, (weather and river conditions permitting). Many of our volunteers carry on outside these months, if it is safe to do, and also monitor redds (non-migratory Trout, and, migratory Salmon & Trout spawning sites). Generally speaking these surveys take a minimum time of one hour.

The data obtained is submitted to us at the Dorset Wildlife Trust: in the event of a reduced count, the Environment Agency is contacted for investigation of a potential pollution incident.