Nitrogen levels in rivers with different catchment land uses
Median nitrogen (both nitrate and nitrite) levels in pastoral and urban catchments are higher than in natural catchments and generally exceed Australia and New Zealand Environment and Conservation Council (ANZECC) guidelines.
Comparison of median nitrogen (nitrate and nitrite) levels in rivers and streams by catchment land use, 1997–2002
| Year |
Measure |
Pastoral (mg/L) |
Natural (mg/L) |
Urban (mg/L) |
ANZECC guideline (mg/L) |
|---|---|---|---|---|---|
1997 |
Median |
0.335 |
0.0775 |
0.93 |
0.306 |
1998 |
Median |
0.31 |
0.08 |
0.82 |
0.306 |
1999 |
Median |
0.366 |
0.0765 |
1.0 |
0.306 |
2000 |
Median |
0.32 |
0.091 |
0.8825 |
0.306 |
2001 |
Median |
0.355 |
0.0905 |
0.6675 |
0.306 |
2002 |
Median |
0.394 |
0.07075 |
0.8 |
0.306 |
Notes:
(1) River environments have been defined using the River Environment Classification. Catchments are defined as ‘natural’ unless pasture exceeds 25 per cent of the catchment area (in which case, it is classed as ‘pastoral’), or unless urban land use exceeds 15 per cent of the catchment area (in which case, it is classed as ‘urban’).
(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.
(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. Catchments are defined as ‘natural’ unless pasture exceeds 25 per cent of the catchment area (in which case, it is classed as ‘pastoral’), or unless urban land use exceeds 15 per cent of the catchment area (in which case, it is classed as ‘urban’).
(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.
(3) mg/L = milligrams per litre.
(4) Hazen method used to calculate 5th and 95th percentiles.
Data source: Ministry for the Environment.
This information has come from the latest state of the environment report, Environment New Zealand 2007.
Return to nitrogen in rivers page.
Last updated: December 2007
