Water quality protected during Somerset Levels dredging 02 July 2014

A monitoring system, supplied by OTT Hydrometry and installed by Wavelength Environmental, is helping to protect water quality on the Somerset Levels during the ongoing dredging operation following this year's floods.

The system, which issues email alerts if water quality deteriorates beyond pre-set conditions, is helping the project team to manage working practices sympathetically with the environment and local ecology.

The Environment Agency estimates there were more than 65 million cubic metres of floodwater covering an area of 65km2.

The monitors consist of Hydrolab water quality sondes and Adcon telemetry systems, which transmit near-real-time data during the dredging operation, due to run well into next winter.

The monitors are anchored to the river bed and suspended in the river by two small buoys. Each sonde is fitted with sensors measuring dissolved oxygen (DO), ammonium, temperature, pH, conductivity and turbidity.

A short cable connects each sonde to an Adcon telemetry unit on the bank, which transmits data via GPRS every 10 minutes.

The sondes contain data loggers, but the transmitted data is available to project staff in near real-time via a web-based data portal.

Simon Browning, from Wavelength Environmental, has been monitoring the data from the sondes and says: "The monitors are quick and easy to deploy, and have performed very well.

"However, portability is extremely important, because the instruments have to be moved and redeployed as the dredging work proceeds.

Browning says the firm has started fitting GPS units to the telemetry systems so that the project team can keep track of the monitoring locations.

"This is important because each dredging team is constantly moving, so the monitors have to be moved regularly," he explains.

Dredging work started at the end of March on the banks of the river Parrett, between Burrowbridge and Moorland, close to Junction 24 of the M5.

Costing £1 million per mile, five miles of river bank will be dredged to restore the river channels to their 1960's profile, so improving their drainage capability.

Brian Tinham

Related Companies
OTT Hydrometry Ltd
Wavelength Environmental Ltd

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