River condition indicator update
July 2013; INFO 689
This page summarises the key findings of the 2013 River Condition Indicator. The indicator provides a national-level picture of the state of our rivers based on six water quality attributes: nitrates, total phosphorus, dissolved reactive phosphorus, bacteria (E.coli), ammonia, and aquatic insects (macroinvertebrate community index). As part of ongoing improvements to national environmental reporting, we are developing more river monitoring sites and better monitoring over longer timeframes for future indicators.
The method behind this indicator is explained in a report by NIWA, and the underlying analysis and raw data is available for download.
- NIWA Report: Statistical models, indicators and trend analyses for reporting national-scale river water quality
- Modelled state, trend and long term change data [Excel, 79 MB]
- Raw site data from Regional Council State of Environment (SoE) and NIWA National River Water Quality Network (NRWQN) monitoring programmes [NIWA website]
For information about your local river see the Land Air Water Aoteoroa (LAWA) website.
River condition indicator summary
This image shows the proportion of monitoring sites with deteriorating of improving trends for some of the parameters that inform this indicator.
Nitrate concentrations are deteriorating in about a quarter of our river monitoring sites. The most significant source of nitrate at a national scale is animal urine: ammonia in urine is rapidly nitrified by bacteria in soil, where it leaches into waterways as nitrate.
Rivers and streams in urban areas tend to have the highest concentrations of nutrients and bacteria, and lowest macroinvertebrate (aquatic insects) health. However, water quality at the relatively small number of monitored sites in urban areas is generally improving. Urban streams make up less than one per cent of the total length of New Zealand’s rivers.
Macroinvertebrates are a biological indicator of river condition, and reflect impacts like changes in water quality and habitat. Macroinvertebrate condition (MCI) declined in more places than it improved.
Urbanisation and agriculture have led to significant increases in phosphorus and nitrogen concentrations in many places.