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ECAN Ignores Nitrate Threat to Freshwater Ecosystems

Ecan’s Chief Scientist Dr Tim Davie a hydrologist recently gave a presentation the first of a planned series on Canterbury water management.

This meeting was to reassure Christchurch City ratepayers that their drinking water was in safe hands under Ecan.

Davie gave a clear presentation of the source of Christchurch groundwater, (2/3 from the Waimakariri River and 1/3 from land surface recharge). He showed how groundwater is contained in a number of confined aquifers beneath the city and explained how the city has sufficient quantities of freshwater and how it is presently allocated and how Christchurch ground water has a large protection zone on the city's NW boundary where there is restricted land use to protect water quality.

Underground Christchurch water was held in “confined” aquifers separated by layers of sediment which slowed the movement of water between the aquifers but they were still connected, said Peter Trolove.

He related that recently groundwater from north of the Waimakariri River has been found to connect with the city's aquifers and this is a threat Ecan is monitoring as it is a threat to the city's water quality because land surface recharge north of the Waimakariri River has very high nitrate pollution.

He said that the community in the water zone north of the Waimakariri was developing more stringent land use plans beyond "good management practice" (GMP) in attempt to manage this risk and that Ecan has an aspirational target limit of 5.6 mg/L N for groundwater sources for human consumption.

When asked about protecting the city's aquatic ecosystems he said Ecan has a default limit of 6.9 mg/l for surface water and that this limit will protect 80 % of freshwater species.

Water resources and the freshwater ecosystem on the Canterbury Plains are being poisoned by excessive nitrate levels says a trout and rivers advocacy group, the NZ Federation of Freshwater Anglers.

President Dr. Peter Trolove, a veterinarian, said nitrate levels and the standards set by ECAN were well above levels which would support fish life.

He pointed out that as nitrate levels around 3.0 mg/L are toxic to trout eggs and fry, which means 100% of our species of interest and probably smelt and possibly other fish cannot reproduce.

Having a hydrologist as a chief scientist reflects Ecan's role as the organization that manages water allocation.

As fishermen and conservationists the Federation would like to see an ecologist as the chief scientist because Ecan's water management has proved to be very damaging to the region's aquatic ecosystems.

"Dr Trolove along with many others with knowledge of water quality requirements for fish are aware that the National Policy Statements for Freshwater Management do not protect many aquatic species yet these are the standards the MfE has developed for government to provide guidance for regional councils such as Ecan. The MfE has belatedly recognized this and new standards are presently being developed.

Dr Trolove is puzzled as to how a community group such as the Waimakariri Water Zone Committee can develop meaningful land use management plans by consensus rather than scientific method.

The nitrate limits for drinking water sourced from rural wells exceed New Zealand and WHO limits in an increasing number of sites in Canterbury.

The MfE limits are inadequate as is obvious to local fishermen who have seen the disappearance of trout from many of Canterbury's smaller low land rivers and streams".

Peter Trolove who has overseas aquatic veterinarian experience, said that ECAN appeared to be seriously under estimating the toxicity of nitrates leaching into the fresh-water systems.

Dr Mike Joy Victoria University did samples in 2018, from 18 of the 28 smaller rivers, streams and drains detecting nitrate levels above 6.8 mg/L.

“Dr Joy’s concerns were that the high levels of nitrates were carcinogenic to those that drink water” said Dr Trolove.

Contact: Dr Peter Trolove (0297 790295).

Yours

Dr Peter Trolove President