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Fresh water River water quality Nutrients
Regional council water quality data, 1997 - 2002
Regional council data for 545 river sites from 1997 to 2002 has been collated to provide a picture of current nutrient levels with the widest possible geographical coverage. This data is due to be updated in 2009.
The nutrient levels in rivers in unmodified (natural) catchments are compared with rivers in pastoral and urban catchments for:
- oxides of nitrogen (dissolved form of nitrogen - includes nitrite and nitrate)
- dissolved reactive phosphorus (dissolved form of phosphorus)
- ammoniacal nitrogen
Oxides of nitrogen
Urban and pastoral streams have the highest nitrogen levels. The median nitrogen levels in both urban and pastoral waterways breach the Australia and New Zealand Environment and Conservation Council (ANZECC) guidelines for ecosystem protection (see note 2 in the table below). Rivers and streams in unmodified catchments, such as those that are covered in native bush or alpine tussock, have the lowest levels of nitrogen measured in New Zealand waterways.
Oxidised nitrogen levels (mg/L) in rivers in pastoral, natural and urban catchments, 1997 - 2002 and the percentage of sites that exceed ANZECC guidelines
| Land use | 5th percentile (best rivers) |
Median | 95th percentile (worst rivers) |
Percentage of sites exceeding ANZECC guidelines |
|---|---|---|---|---|
| Pastoral (355 sites) | 0.021 |
0.347 |
3.426 |
52.5 |
| Natural (135 sites) | 0.011 |
0.081 |
0.497 |
9.6 |
| Urban
(26 sites) |
0.198 |
0.850 |
2.214 |
86.6 |
Notes:
(1) River environments have been defined using the River Environment Classification.
(2) The ANZECC guidelines provide ‘trigger values’ for the protection of ecosystems and the recreational and aesthetic values of waterways. If a trigger value is reached, it does not necessarily mean that ecosystem damage is occurring or that recreation is no longer possible, but it provides advance warning that a problem may be emerging. The ANZECC guideline used is the average of the values for lowland and upland rivers.
(3) mg/L = milligrams per litre.
(4) Hazen method used to calculate 5th and 95th percentiles.
Data source: Ministry for the Environment.
(1) River environments have been defined using the River Environment Classification.
(2) The ANZECC guidelines provide ‘trigger values’ for the protection of ecosystems and the recreational and aesthetic values of waterways. If a trigger value is reached, it does not necessarily mean that ecosystem damage is occurring or that recreation is no longer possible, but it provides advance warning that a problem may be emerging. The ANZECC guideline used is the average of the values for lowland and upland rivers.
(3) mg/L = milligrams per litre.
(4) Hazen method used to calculate 5th and 95th percentiles.
Data source: Ministry for the Environment.
Comparison of median nitrate nitrogen levels in rivers and streams by catchment land use, 1997–2002
Notes: as per table above.
Data source: Ministry for the Environment.
Read table of data of this graph
Dissolved reactive phosphorus
Urban streams have the highest dissolved reactive phosphorus levels, followed by rivers and streams in predominantly pastoral catchments. The median dissolved reactive phosphorus levels in both urban and pastoral waterways breach the ANZECC guidelines for ecosystem protection. Rivers and streams in unmodified catchments, such as those that are covered in native bush or alpine tussock, have the lowest levels of dissolved reactive phosphorus measured in New Zealand waterways.
Dissolved reactive phosphorus levels (mg/L) in rivers in pastoral, natural and urban catchments, 1997 - 2002 and the percentage of sites that exceed ANZECC guidelines
| Land use | 5th percentile (best rivers) | Median | 95th percentile (worst rivers) | Percentage of sites exceeding ANZECC guidelines |
|---|---|---|---|---|
| Pastoral (355 sites) | 0.002 |
0.014 |
0.101 |
66.1 |
| Natural (135 sites) | 0.002 |
0.008 |
0.032 |
45.2 |
| Urban (26 sites) |
0.007 |
0.017 |
0.173 |
90.2 |
Notes: as per table above.
Data source: Ministry for the Environment.
Data source: Ministry for the Environment.
Comparison of median dissolved reactive phosphorus levels in rivers and streams by catchment land use, 1997–2002
Notes: as per table above.
Data source: Ministry for the Environment.
Data source: Ministry for the Environment.
Data (text description) for graph
Ammoniacal nitrogen
Urban streams have the highest ammoniacal nitrogen levels, followed by rivers and streams in predominantly pastoral catchments. The median ammoniacal nitrogen levels in both urban and pastoral waterways breach the ANZECC guidelines for ecosystem protection. Rivers and streams in unmodified catchments, such as those that are covered in native bush or alpine tussock, have the lowest levels of ammoniacal nitrogen measured in New Zealand waterways.
Ammoniacal nitrogen levels (mg/L) in rivers in pastoral, natural and urban catchments, 1997 - 2002 and the percentage of sites that exceed ANZECC guidelines
| Land use | 5th percentile (best rivers) | Median | 95th percentile (worst rivers) | Percentage of sites exceeding ANZECC guidelines |
|---|---|---|---|---|
| Pastoral (355 sites) | 0.005 |
0.020 |
0.136 |
59.1 |
| Natural (135 sites) | 0.001 |
0.008 |
0.050 |
26.5 |
| Urban (26 sites) |
0.004 |
0.050 |
0.921 |
77.9 |
Notes: as per table above.
Data source: Ministry for the Environment.
Data source: Ministry for the Environment.
Comparison of median ammoniacal nitrogen levels in rivers and streams by catchment land use, 1997–2002
Notes: as per table above.
Data source: Ministry for the Environment.
Data source: Ministry for the Environment.
Read table of data of this graph
Want to know more?
About river water quality in your region, refer to your local council's website or refer to the background technical report on the Ministry's website.
This information has come from the latest state of the environment report, Environment New Zealand 2007 and the technical summary, Regional Council Water Quality Data (1996–2002).
Last updated: December 2007
