Urgent action needed to stop Ashburton lakes 'turning to sludge'
Wednesday, 28 July 2021
The water quality in several beloved Canterbury lakes has degraded so badly that urgent action is needed to stop them crossing a dangerous threshold.
A new scientific report commissioned by Environment Canterbury (ECan) and the Department of Conservation (DOC) found “significant reductions” in nutrients like nitrogen were needed to save Ashburton’s high country lakes.
The study included lakes Heron, Emily, Clearwater, Camp, Emma, and Denny, and two of the Māori Lakes.
ECan science director Tim Davie said many of the lakes were at risk of “flipping”, in which they would be dominated by algae blooms.
**READ MORE:
* Concern as nitrate levels rise in half of wells tested in Canterbury
* Freshwater reforms and farmers: two sides of the same coin
* ECan councillor says proposed plan changes don't go far enough to protect drinking water
**
Once that happened, it was extremely hard to get them back to their natural states.
“Lakes are often accumulators of nutrients, and legacy issues can persist for years after nutrient loads are reduced. Climate change is likely to further increase this vulnerability,” he said.
“This means that to make any positive improvements there will need to be substantial and urgent action in the catchment.”
Davie said a working group had been set up and needed to focus on action now they had clear scientific data.
ECan councillor Lan Pham said she was “extremely concerned” by the report, which showed several sources were responsible for the pollution.
“No matter what those sources are, we need to do everything possible to eliminate them.
“To have these lakes turn to sludge on our watch is an indictment of where our meagre rules and regulations are so far away from being up to scratch.”
ECan could not come up with a “magic wand” regulation overnight to get landowners to use their land differently, so action from the community, and more importantly from Central Government, was needed.
The report was clear that action needed to happen quickly, she said.
“It’s now or never.”
Pham said the same planning and rules applied to the rest of Canterbury, and it was a region full of sensitive lakes, braided rivers, and a complex groundwater system.
“We’re so far from adequate regulations to protect the quality of our water … we cannot continue like this if we’re serious about having a future for our kids and grandkids.”
The report also studied five lakes in the Selwyn district – Lyndon, Grasmere, Pearson, Sarah and Hawdon – and found they also needed moderate to large nutrient load reductions to meet plan objectives.
The findings suggested high-country lakes across the region might need help.
Davie said the science showed more than one factor was causing the lakes’ degradation.
“While farming land use is a contributor, so are the impacts of amenity users and birdlife.
“The situation is further complicated by differences between each of the lakes. There is no single solution that will address these issues.”
The working group had considered several actions, including using the data to find options for individual farms in each catchment area, new requirements for sewage systems in Lake Clearwater village, and more work to understand what effect water birds were having on nutrient levels in the lakes.
DOC aquatic director Elizabeth Heeg said they were particularly concerned about the effect of declining water quality on the lakes’ ecology.
“This area contains a diverse range of ecosystems that provide nationally and regionally important freshwater habitats for threatened and at risk native birds, fish, and invertebrates.
“Many of these freshwater habitats and species are sensitive to nutrient enrichment.”
Heeg said DOC was committed to working closely with Environment Canterbury, mana whenua and landowners to halt and reverse the declining water quality.
Farmers used fertilisers to add nutrients like nitrogen to soil. The nutrients were ingested by cows and excreted, eventually trickling into waterways.
It was something environmental advocates had long been calling for stricter limits on, with some, like Greenpeace, calling for synthetic nitrogen fertiliser to be banned and the number of dairy cows to be slashed.
Many of the lakes in the Ashburton high country system, or Ō Tū Wharekai, were culturally significant to Canterbury rūnanga, and were important historical food gathering and mahinga kai sites.