Lobby group Fish & Game wants a cap placed on the volume of nitrogen leached into Taranaki's waterways.
Fish & Game Taranaki will make the call for a maximum in a submission to the Taranaki Regional Council's freshwater plan review - even though the council has already indicated it is not keen on a cap.
A nitrogen cap would limit algal growth, protect ecosystems and improve the water quality of Taranaki rivers, according to Fish & Game Taranaki officer Allen Stancliff.
An Agresearch study of the Waiokura Stream near Manaia between 2001 and 2008 showed nitrogen levels rose by 14 per cent, as sediment and E.coli bacteria fell by 40 per cent and phosphorus by 30 per cent, Mr Stancliff said.
Nitrogen and phosphorus run-off can make some aquatic plants and algae thrive and multiply, changing the ecological balance of waterways and damaging native eel and whitebait habitats, restricting swimming, boating and fishing, and ruining aesthetic appeal.
Federated Farmers dairy president Derek Gibson is opposed to a nitrogen cap.
"It's not something farmers want. If we can keep improving water quality, we think we won't need one."
The nitrogen cap call comes in the wake of the comments from the New Zealand Freshwater Sciences Society which expressed dismay at what it saw as the rapid and widespread decline of New Zealand's aquatic biodiversity and water quality.
The society held its annual conference last week and its president, Waikato University professor David Hamilton, told the Daily News land use intensification, increasing levels of nutrients and sediment and higher stock numbers were reducing freshwater health.
Despite his call for a cap, Mr Stancliff believes Taranaki is protecting its waterways well.
"Taranaki is leading the way in terms of its riparian programme.
"If we can't manage our short, steep streams, there's not much hope for the rest of the country," he said.
Fish & Game agreed with the regional council's report card last month that said water quality was being maintained and improving at some monitoring sites in Taranaki, even though land use continued to intensify.
The report card showed Taranaki water was pristine in waterways in the Egmont National Park, but quality declined on its journey to the sea.
Mr Stancliff said a regional council proposal for dual effluent disposal systems that let farmers spray effluent on land or discharge it to water, depending on conditions, would improve river quality.
At present about 1000 Taranaki farmers discharged effluent to water, 8 per cent had a dual system and the remainder put effluent on land.
Mr Gibson said farmers had concerns about the regional council proposal and Federated Farmers and DairyNZ were discussing it with the council.
Rachel Stewart on water quality: P8.
- © Fairfax NZ News
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