EW trials catchment focus to improve water quality

Regional council Environment Waikato has been working closely with farmers to help them be more profitable while protecting the environment better by reducing nutrient leaching and run-off to waterways.

This work - a trial of Integrated Catchment Management (ICM) in the South Waikato’s Little Waipa and Waipapa stream catchments - is currently being evaluated to help decide how the project will be developed.

The project involves EW staff working one-on-one with dairy farmers.

The ICM studies will help ensure real world farm data is used in the council’s policy planning as it seeks to cut nutrient losses from farms.

It is also intended the studies will provide the basis of future work with DairyNZ, Fonterra and Ballance in the Upper Waikato Catchment – home to the region’s hydrolakes - where further case studies will be undertaken to help better understand the scale of the challenge faced when it comes to protecting water quality.

Ongoing environmental monitoring by EW highlights many regional waterways were facing increasing trends in levels of nutrients and many waterways had higher levels of bacteria than would be desired.

ICM has involved making initial assessments of land use, farming intensity and production, and estimates of bulk nutrient loss in the catchments to compare with 13 years of in-stream monitoring by EW.

EW has worked directly with the farmers and the fertiliser representatives on nutrient budgets and nutrient management plans as a first step before catchment-wide assessments are made.

Farms are assessed against modelled targets and nutrient management scenarios are developed with a view to lowering nitrate leaching or phosphate runoff on a catchment-wide basis.

The farmers EW has worked with have been very positive about the plans developed to help them individually achieve reductions as they give a current snapshot of farm systems and a shortlist of actions they can take.

On a regional basis, initial modelling - to show how current water quality could be maintained in the Waikato’s hydrolake system - highlights that farmers collectively would need to lower nitrate leaching from dairy operations from the current annual average of around 40kg of nitrogen per hectare to below 26kgN/ha.

EW estimates the current suite of best practice changes on farm would typically lower leaching by around 10kgN/ha without large changes in farm production or profitability, which is a really positive start. But given that at least a further 4kg improvement is needed, EW continues to work with farmers, backed up by science from AgResearch, to help find ways of making bigger reductions.

The council is now working with the dairy and fertiliser industry to check its modelling and to assess on-farm practices with a larger number of case study farms in the wider South Waikato area. This aims to identify what makes a farm system “nutrient efficient” and to assess the cost and benefits of making changes.