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Figure 10.3: Nutrient trends in rivers in the national monitoring network, 1989–2005

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Nitrate Nitrogen

Total Nitrogen

Ammoniacal Nitrogen

Dissolved Reactive Phosphorus

Note:

mg/L = milligrams per litre.

Source: Adapted from Ministry for the Environment, 2006d.

Text description of figure

Figure showing map of national monitoring network locations and graphs of average nutrient trends across the network.  The map shows that 33 of the 77 sites are in the South Island and the remainder in the North Island (that is, there are approximately equal numbers of sites in each island and they are fairly evenly distributed across the landscape).

Nitrate Nitrogen

 

 

Rivers with lowest concentrations
(5th percentile)
(mg/L)

Median rivers
(50th percentile)
(mg/L)

Rivers with highest concentrations
(95th percentile)
(mg/L)

1989

0.0162

0.1400

0.6835

1990

0.0107

0.1050

0.6478

1991

0.0080

0.0980

0.7290

1992

0.0107

0.1000

0.7851

1993

0.0054

0.0590

0.5838

1994

0.0087

0.0830

0.7098

1995

0.0087

0.1275

0.8489

1996

0.0082

0.1035

0.7303

1997

0.0069

0.0965

0.7714

1998

0.0054

0.0935

0.7577

1999

0.0066

0.1215

0.8985

2000

0.0051

0.1045

0.8163

2001

0.0046

0.1440

0.7640

2002

0.0071

0.1110

0.9673

2003

0.0059

0.1420

0.8353

2004

0.0042

0.1145

1.0008

2005

0.0042

0.1155

0.9486

 

Total Nitrogen

 

Rivers with lowest concentrations (5th)
(mg/L)

Median rivers
(mg/L)

Rivers with highest concentrations (95th)
(mg/L)

1989

0.0609

0.2525

0.9863

1990

0.0457

0.2500

1.0030

1991

0.0400

0.2200

1.0390

1992

0.0518

0.2500

1.0085

1993

0.0559

0.2250

0.7434

1994

 

 

 

1995

0.0424

0.2225

1.1074

1996

0.0450

0.2225

1.0085

1997

0.0526

0.2285

1.1241

1998

0.0595

0.2430

1.0849

1999

0.0599

0.2730

1.0730

2000

0.0591

0.2240

1.1626

2001

0.0617

0.2815

1.1152

2002

0.0584

0.2670

1.1744

2003

0.0500

0.2680

1.0044

2004

0.0647

0.2695

1.2668

2005

0.0549

0.2795

1.1445

 

Ammoniacal nitrogen

 

Rivers with lowest concentrations (5th)
(mg/L)

Median rivers
(mg/L)

Rivers with highest concentrations (95th)
(mg/L)

1989

0.006

0.009

0.032

1990

0.004

0.007

0.033

1991

0.004

0.007

0.025

1992

0.005

0.008

0.029

1993

0.004

0.007

0.028

1994

 

 

 

1995

0.003

0.006

0.025

1996

0.003

0.006

0.043

1997

0.002

0.005

0.049

1998

0.002

0.005

0.043

1999

0.002

0.006

0.037

2000

0.002

0.005

0.034

2001

0.002

0.005

0.038

2002

0.002

0.005

0.041

2003

0.001

0.004

0.034

2004

0.001

0.005

0.032

2005

0.001

0.004

0.041

 

Dissolved reactive phosphorus

 

Rivers with lowest concentrations (5th)
(mg/L)

Median rivers
(mg/L)

Rivers with highest concentrations (95th)
(mg/L)

1989

0.0010

0.0045

0.0210

1990

0.0010

0.0045

0.0237

1991

0.0010

0.0040

0.0240

1992

0.0004

0.0040

0.0279

1993

0.0002

0.0040

0.0293

1994

0.0005

0.0040

0.0297

1995

0.0008

0.0053

0.0293

1996

0.0009

0.0057

0.0275

1997

0.0006

0.0056

0.0382

1998

0.0006

0.0048

0.0302

1999

0.0006

0.0065

0.0279

2000

0.0009

0.0058

0.0271

2001

0.0008

0.0062

0.0316

2002

0.0008

0.0052

0.0267

2003

0.0005

0.0043

0.0292

2004

0.0006

0.0047

0.0214

2005

0.0007

0.0050

0.0221