Lake Aviemore, a popular holiday spot, is one of the locations in the Upper Waitaki under the microscope for its declining water quality. (File photo)
An Environment Canterbury science advisor has released a report warning about the large-scale declining quality of rivers and lakes in the Upper Waitaki catchment.
ECan principal science advisor Graeme Clarke, who presented the report at Friday’s Upper Waitaki zone committee meeting in Tekapo, said several of the catchment’s lakes and waterways were declining according to the Trophic Level Index (TLI).
These included Lake Alexandrina, Lake Pukaki, Lake Ōhau, and Kellands Pond, all of which exceeded their recommended limits. Others, including Lake Aviemore, were within their limits but had recorded a higher TLI.
The TLI is used across the country as a measure of the nutrient status of a lakes and waterways. A higher reading results from higher nutrient concentrations and higher algal biomass (phytoplankton). Lakes with high TLIs generally have greener and more turbid (cloudy) water.
The Ahuriri River at Ben Omar, Omarama Stream, Sutherlands Creek, Twizel River, Wairepo Creek and Willow Burn all have reported increased Nitrogen levels.
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Clarke’s report says while this does not necessarily mean these lakes and rivers are unsafe for swimming, it does mean more monitoring would be needed in the future.
He said he was “not surprised” by the results.
“In general, the large lakes in the Upper Waitaki such as Ōhau, Pūkaki and Tekapo/Takapō are still in very good health with low nutrient levels, but the results from the past year’s monitoring have shown a decrease in water quality compared to last year,” Clarke said.
“The change could be linked to heavy rainfall experienced in December 2019, which can wash nutrients and sediment from land into the waterways. It’s important to note that this monitoring is different to swimming and contact recreational water quality – which shows that all sites in the zone are suitable for swimming.”
ECan Southern Zone Manager, Chris Eccleston, said the results reaffirmed the importance of measures being taken to reduce the impact of both farming and aquatic pests on the waterways.
“The implementation of on-farm good management practices across the zone and, longer-term, implementation of policies in the Government’s new Essential Freshwater Management framework will address key causes of degradation. Over the past five years, we’ve been working closely with both irrigators and farmers in the area to implement tighter environmental rules.”
However, Eccleston said that Farm Environment Plans (FEPs) and Good…