River data flows without a break
Hundreds of walkers pass the Teachers College tower daily. asks what goes on inside.
The Manawatu Teachers College’s name lives on at a little hut overlooking the Manawatu Riverside shared pathway, just upstream of Palmerston North’s Fitzherbert Bridge.
The station sits atop a 5-metre tower over a deep well extending 8m down into the bed of the river, and is a key part of the Horizons Regional Council’s catchment monitoring network.
Senior catchment data coordinator Paul Peters is often at the historically-named ‘‘Manawatu at Teachers College’’ site.
River observations have been taken from the site at Centennial Drive since the 1880s, and have been recorded constantly since 1928, the longest continuous records of any observation site in New Zealand.
A key role is flood prediction, triggering automated alerts to up to 300 customers downstream to shift stock, secure assets and reduce the impact of flooding, and informing the decision about when to open the Moutoa floodgates.
Water level information is scanned every 15 seconds, recorded every five minutes, and transferred back to the telemetry system to go live on Horizons’ website every half hour.
A simple float measures the water level, above an historic baseline of 21.209m above sea level, double-checked by more modern technology.
There is a simple ruler in the river to check that the sensors are performing correctly.
Low flow recordings trigger controls on whether consent holders are allowed to draw water, and signals to the Palmerston North City Council to remove phosphorus from its wastewater discharge.
It is used for monitoring the health of the river through indicators such as clarity, nitrate, E coli and dissolved oxygen levels.
Pumps raise ‘‘grab samples’’ to the hut, which traditionally have had to be taken away for analysis, but is increasingly measured hands-free.
In 2013, the tower was lifted 90 centimetres to stand above stopbanks raised to withstand a one-in-500-year flood.
Peters said staff considered whether the walkway to the tower – designed to support 23 people – needed to be sealed off.
On balance, the decision was made to install steps so people could access the viewing platform and feel part of the river’s guardianship team.