Nukuhou River's nitrogen decline of 3.4 per cent in 10 years is the highest in whole of Bay of Plenty.
Farmers in the Nukuhou River catchment are being credited for clinching this year's Bay of Plenty most improved river title.
The award was presented to council chair Doug Leeder at a ceremony in Wellington last week as part of the Morgan Foundation's annual River Awards.
Eastern catchments manager Simon Stokes said it recognised the hard work landowners had done to protect the river over the past several years.
Bay of Plenty Regional Council became involved about 10 years ago, providing technical expertise and financial support at the landowners' request, he said.
Data showed between 2005 and 2015, expenditure by regional council was $775,086 and $682,842 by landowners.
Since then farmers had installed another 49km of riparian fencing, built six bridges to allow stock to cross the river without walking through the water, upgraded stock races to avoid run-off going directly into the streams, retired and planted a further 333ha of steep land and planted 48,000 native plants, mostly on riparian margins.
The Ohiwa Harbour Implementation Forum and Ohiwa Harbour Strategy Care Group had also worked closely with council and played a huge part in improving the river, Mr Stokes said.
"The forum has done a fantastic job overseeing river projects and monitoring council's work with landowners to ensure the [Ohiwa Harbour] strategy delivers for the environment," he said.
Work to protect and improve the Nukuhou River continued, with the regional council working with farmers to develop and use nutrient management plans to identify ways to address the more diffuse nutrient leaching sources from animal urine and fertiliser use.
The most improved rivers were determined by the trend decline in dissolved inorganic nitrogen (DIN). The Nukuhou River had recorded a 3.4 per cent decline in DIN since 2005, which continued a steady trend decline that had been evident since 1995.
Huge pressure on water quality
Nukuhou River is the biggest tributary of hiwa Harbour, a place of significant ecological importance that is highly valued by locals and visitors.
The river catchment is very small, at 100sq km, and most of it is in agriculture of one sort or another. There are 16 dairy farms, eight drystock farms and some small operations. This means there is huge pressure on the water quality of the river.
The regional council consented dairy effluent discharges following the adoption of the Resource Management Act in the early 1990s.
It inspects all dairy sheds regularly, either annually or every three years depending on the type of effluent system and each farm's history of compliance.