Millbrook removes 3,000 tonnes of sediment
Friends of Lake Hayes are delighted to recognise the work Millbrook Resort and its residents have done over the past 12 months to reduce the sediment and nutrients reaching Lake Hayes.
Working with FOLH on lake water quality, Millbrook has been removing built-up sediment from the ponds across its site. A remote-controlled dredge pumped sediment from the ponds through a pipeline into large collection and filtering bags. The bags let the water drain away and hold the sediment, which then dries out and can be removed. Around 5,000 tonnes of sediment have been taken out so far.
Sediment carries phosphorus, the main nutrient behind the lake’s algal blooms. Left in the ponds, this sediment would be stirred up in floods and washed downstream into the lake. Every tonne of sediment carries roughly 1 kg of phosphorus, so FOLH estimates this work has kept around 5 tonnes of phosphorus out of Lake Hayes. To put the sediment figure in context, FOLH’s target is to limit the total sediment reaching the lake to 300 tonnes a year.
The pipeline carrying sediment from the ponds to the collection and filtering bag. The remote-controlled dredge at work in one of Millbrook’s ponds. The second bag being filled, with the dried 2,500-tonne pile from the first bag on the right September 2026 floods: the wetlands filling and reducing the sediment load reaching the lake. September 2026 floods: the wetlands filling and reducing the sediment load reaching the lake. Mill Creek with the recreated wetland and flood plain holding back floodwater.
Mill Creek back where it belongs
As part of redeveloping the Coronet golf course, which has recently hosted the New Zealand Open, Millbrook moved Mill Creek back to its original course running parallel to Streamside Lane. This recreated a large wetland and flood plain (see photo 6).
The August 2026 floods put it to the test. As the photos show, the wetland filled as intended, spreading the water out and taking the peak off the flood. Slowing the water lets sediment settle on the flood plain instead of travelling to the lake. It’s estimated around 50 tonnes of sediment was held back in this one event.
This is exactly what “fix the catchment and you’ll fix the lake” looks like in practice: natural wetland systems doing the work they did before 90% of the catchment’s wetlands were lost.
A big thank you from the lake
Millbrook and its resident landowners have invested significant time and money in this project. On behalf of the lake, thank you to Millbrook and its residents.