Te Waihora can be restored to good health - ecologist

Te Waihora/Lake Ellesmere may have a reputation for being one of the most polluted lakes in New Zealand, but Canterbury University Freshwater Ecology Professor Jon Harding is optimistic about the future of the iconic lake.

Improving the lake’s water quality “won’t be an easy fix” he told the recent Whakaora Te Waihora science hui, but with time and help he believes Te Waihora can be restored to good health.

Professor Harding and his team, known as the CAREX project, have been involved in large-scale experiments looking into the restoration of waterways flowing into Te Waihora.

The project is unique in New Zealand and the team of eight, four of whom are working full time on the project, is stretched by the ambitious undertaking – a study that includes a one-kilometre stretch on 10 different Canterbury waterways from Rangiora to Hinds. Two of these are in the Te Waihora catchment.

Funded by the Mackenzie Charitable Foundation of Ashburton, the CAREX project involves the joint restoration programme Whakaora Te Waihora, Environment Canterbury, the Fonterra / Department of Conservation Living Water initiative, Waimakariri District Council, Fish & Game and the Institute of Environmental Science & Research.

Professor Harding and his team are already six years into the project and the initial small-scale proof of concept experiments are now being scaled up over larger areas on the selected waterways. The project will run for four more years.

“There has always been a lot of focus on the health of the lake itself, but I believe it is critical that restoration starts at the top of the catchment,” Professor Harding said.

“You can do no end of things inside the lake but the reality is, the source of many of the contaminants lies in the waterways that feed into the lake. We believe absolutely that surface water research needs to start at the top - in the small drains and streams that ultimately deliver problem sediments and excess nutrients into the lake much further downstream.”

Professor Harding said that even if significant positive results may not be seen for decades, small, gradual, manageable steps will have an impact.

“The polluted lake we have today is the legacy of 150 years of intensifying land use,” he said. “Unfortunately, many people have tended to view waterways as dumping grounds – that dilution is the solution – but that’s a fallacy. Waterbodies have limits to the levels of contaminants they can process and Te Waihora has gone past that limit.

“That said, streams, rivers and lakes have a remarkable ability to recover from almost anything with the right restoration programmes applied over time.

“This is a long-term project but I’m optimistic that improving water quality and bio-health in upstream systems will have significant benefits for Te Waihora.”

The CAREX project is focused on three key issues - the excessive fine sediment loads being exported into the lake; the high nutrient levels, especially nitrates and sediment-bound phosphorous; and the nuisance aquatic weeds such as monkey musk and watercress that choke waterways, raise water levels and accumulate sediment.

“It’s an ambitious undertaking but in the next six to nine months we’ll see if our experiments work or not,” Professor Harding said. “It’s all about working out how we might successfully restore these waterways, at the same time giving catchment landowners the tools to make a difference to the quality of water flowing into Te Waihora.

“Te Waihora is unique in New Zealand. It’s by far the biggest lowland lake in the country and it should be the jewel in our crown. With the right tools in place, we can restore it to good health,” Professor Harding concluded.

For more information on the Whakaora Te Waihora joint restoration programme, including all the presentations to the science hui held at Lincoln earlier in November, go to www.tewaihora.org,