Water quality measures need work

A Ministry of Environment report shows that water quality in New Zealand is improving.

Water quality is improving in New Zealand - it's official. In late July the Ministry for the Environment released their Water Quality Report (2000-2010) State of the Environment, which showed that overall concentrations of nutrients and bacteria are stable, or improving, at most monitored sites. It also showed that water quality is generally improving in both urban and pastoral areas.

The report was based on data collected from hundreds of sites over a 5- to 10-year period; and the results are a solid endorsement that things are generally on the right track across the country.

The Ministry intended the report as an indicator of the state of play at a national level, while work is ongoing to improve the robustness of environmental monitoring and reporting.

A key area for improvement should include the currently crude classification of sites as being either "urban" or "pastoral".

The data presented in the report shows rivers and streams in, or downstream of, urban areas have the highest concentrations of nutrients and bacteria. The report notes, however, that urban streams make up less than 1 per cent of the total length of New Zealand rivers.

By contrast, nearly 50 per cent of New Zealand waterways are classified as being in catchments predominantly in pastoral land-use. Rivers and streams in pastoral catchments have the widest range in concentrations, from the highest in the country to some of the lowest.

The report speculates that such variability may be due to high variability in erosion risk, combined with a range of land-use intensities associated with different farming types. Indeed it may be. Or it may be due to the varying contributions of towns and cities in predominantly "pastoral" catchments.

Currently, an area with greater than 25 per cent pasture will be classified "pasture" unless the urban land-cover is greater than 15 per cent. Very few sites meet this threshold.

From more than 700 sites in the national database, just 13 are classified urban. Seven of these sites are in Auckland, three in Wellington, two in Nelson and one in Northland.

Every other town and city in New Zealand - from Carterton to Christchurch, Hokitika to Hamilton - is missing from the dataset. Or, more accurately, they have disappeared into a "pasture" category.

Across most catchments in New Zealand, land-use is a matrix of town and country, and both can take credit for efforts to maintain and improve water quality.

The next national environment report should reflect that continued improvements are mostly likely to be the result of town and country working together - not "pastoral" shouldering either the brickbats or the bouquets for everything outside Auckland.