In August 2003 Posford Haskoning, a leading Engineering Consultancy in the UK, contracted OTT Hydrometry Ltd (OHL) to design, deploy, and manage a system of four water quality monitoring buoys on the lower tidal reach of the River Tyne in northeast England. The system is based on an integrated solution that combines the strength of products from Hydrolab and OTT to provide a complete turnkey solution for the site.

The Tyne is home to a number of shipbuilders, and has been heavily polluted by industry, combined with inputs from wastewater plants and other industrial and domestic sources. A commitment to improve water quality over the past 30 years has seen substantial gains, and now the return of salmon, absent from the Tyne for many years, is a realistic ambition.

When plans were made to put a second tunnel under the river to ease traffic congestion between the town of South Shields and the city of Newcastle, the local Environment Agency office decided that water quality monitoring was needed to show that the construction activity was not causing any adverse impact on the water quality. A monitoring program was designed using four monitoring buoys.

All four buoys – two on the south side of the river and two on the north – monitor dissolved oxygen, conductivity (& salinity), temperature, and turbidity. The buoys are arranged in a rectangle at locations upstream and downstream of the new tunnel location. One buoy near each bank also monitors velocity and direction of flow.

The system will be deployed for two years to gather pre-construction baseline data. The system will then be in place during tunnel construction, and for two years after construction for further data collection.

The four systems use 1.5-m diameter "doughnut" buoys powered by two solar panels. The sensor system is based on a Hydrolab DataSonde 4a unit, outfitted with the new self-cleaning turbidity sensor, combined with an oceanographic velocity current meter with on-board compass for directional input. The current meters are on stainless steel arms, while the Sondes are housed in tubes that are attached to the frame of the buoy, which automatically puts these instruments at the same depth when deployed.

Data from the sensors is relayed to an OTT LogoSens datalogger in a waterproof housing in the center of the buoys. The unit logs and manages data locally and transmits the data via GSM telemetry to Ott Hydrometry’s office in Nottingham.

OHL performs maintenance and data management, and the client receives regular reports on the system, including calibration reports, non-routine and routine maintenance reports, and monthly data reports for all parameters at all sites.

Data management uses OTT’s Hydras 3 software to routinely poll the remote sites to acquire data and routine station management information. Below is a typical graphical output showing salinity data and tidal influence from all four sites.