Lake water quality worry could be laid on farming
Farmers adjoining the Ahuriri arm of Lake Benmore could be ordered to reduce nutrient discharges as ‘‘trigger levels’’ for water quality are reached.
The level, known as the Trophic Level Index (TLI), is used as a measure of the nutrient status of a lake. It has exceeded 2.75 in the Ahuriri arm catchment, meaning there is a risk of algal blooms and increased turbidity in the lake. Last year, the TLI was 2.3.
Environment Canterbury southern zone manager Chris Eccleston said a regulatory process had been triggered and an independent panel would determine whether 10 consent holders were responsible for the increase in the TLI.
If the panel determines they are, then the farmers would have to reduce their nutrient discharges by 5 per cent. If this does not bring the levels down to the acceptable TLI, then there will be further compliance measures.
‘‘I liken this to a doctor’s checkup. We know there has been a spike in TLI levels; what we don’t know precisely is what caused it.
‘‘If it wasn’t for the consents being developed the way they were, then we wouldn’t be able to respond so quickly,’’ Eccleston said.
The TLI levels were set at 2.75 for the catchment as a result of the Upper Waitaki consent hearings from 2009 to 2011. This is the first time the Ahuriri arm of Lake Benmore has reached this trigger level since the consents were approved.
ECan water quality scientist Dr Graeme Clarke said the spike was confirmed in June.
‘‘We take a number of samples over the summer. There’s a bit of climatic fluctuations year-in year-out. We’re having a conversation with the consent holders and working with them.
‘‘There are a number of consent holders who have a trigger level above 2.9, so those could well be affected in the near future.’’
Eccleston said the health of waterways is paramount and they were taking prompt action.
‘‘We’ve been in touch with the consent holders impacted to begin the process.’’
Eccleston said it was also in the process of establishing an Ahuriri catchment group to progress implementation of good management practices across farms in the area.
‘‘The good thing about the consents is the fact that it did set these limits, so it means we can act quickly when there’s been a breach,’’ he said.
‘‘We’re hoping to get everything sorted before the start of the next irrigation season in October. This is a collective effort.’’