Enhanced water monitoring for Te Waihora

A similar water monitoring system on Lake Waikaremoana in the North Island.

A similar water monitoring system on Lake Waikaremoana in the North Island.

In the months ahead, a new water monitoring system in Te Waihora/Lake Ellesmere is expected to improve overall management of the lake.

Tim Davie, Surface Water Resources and Ecosystems Manager, Environment Canterbury and Whakaora Te Waihora Workstream Leader, Science, hopes two new monitoring buoys will be installed in the lake in the next three or four months, pending approvals, and he is confident they will produce a data set that will be more useful for understanding the lake.

Current water quality monitoring in Te Waihora consists of monthly samples taken at four sites around the lake. These are sent to a laboratory for analysis of a range of attributes. There are also two conductivity meters in the lake providing continuous records that are downloaded at the same time the samples are taken.

“This monitoring is good for detecting long term changes in water quality parameters and for deriving a lake trophic level index (TLI) but tells us very little about short term changes in lake water quality,” Tim says.

The Lake Waikaremoana fixed sensor buoy underwater.

The Lake Waikaremoana fixed sensor buoy underwater.

The Whakaora Te Waihora science research on nutrient processing being done by a team lead from the University of Otago has highlighted short term changes in dissolved oxygen and other parameters, as being important for understanding and managing the lake. Technology now exists to provide continuous monitoring of water quality from stations in the lake that telemeter the information back to Christchurch every two or three hours. These water quality data are then able to be displayed on the web for any interested stakeholder to view.

Tim says the two new telemetered water quality monitoring systems to be installed in the lake will replace the two conductivity meters already in place mid-lake and near the lake opening at Taumutu. The lake opening near Taumutu is the most dynamic area of the lake; it’s where the sea enters and has the most impact. The centre of the lake is the most representative of the rest of the lake area.

“Adding these water quality monitoring stations provides a rare opportunity to greatly enhance our scientific understanding of the short term variations in water quality. When combined with the knowledge we have gained from the Whakaora Te Waihora research work on nutrient processing, there is an opportunity to improve our lake management using the new monitoring data.

LimnotrackTim acknowledges that installing the buoys could be challenging. They have been used previously in much deeper North Island lakes with good water clarity. Te Waihora is much shallower, has poor water clarity and gets extreme winds. This means the buoys will face greater physical challenges from the wind.

However, Alex Ring, who has been maintaining the conductivity meters in the lake for the past six years, has spent a lot of time investigating alternatives for these types of stations.

He has been in close contact with Professor David Hamilton’s team at the University of Waikato, which has proven expertise in working with these monitoring systems, along with the Cawthron Institute staff, Dr Marc Schallenberg from the University of Otago, NIWA staff, Adrian Meredith from Environment Canterbury and Environment Southland staff concerning their monitoring of Waituna Lagoon. From this, Alex has come up with a monitoring station design to specifically meet Te Waihora conditions. It uses sensors and telemetry supplied by Chris McBride of the University of Waikato.

Ongoing maintenance of the monitors will be carried out by Environment Canterbury and live monitoring data will be available on their website.

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