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Figure 10.10: Trends in macroinvertebrates (%EPT) in rivers in the national monitoring network, 1989–2005

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Notes:

  1. Data is derived from 66 sites of the 77 that make up the national monitoring network.

  2. Higher %EPT indicates better water quality.

Data source: National Institute of Water and Atmospheric Research.

Text description of figure

Group

Rivers with lowest %EPT
[5th percentile]

Rivers with median %EPT

Rivers with highest %EPT
[95th percentile]

1989

0.511346

37.3598

82.4518

1990

1.04073

40.335

91.9269

1991

1.95021

50.9064

92.3474

1992

0.718243

40.0522

94.1071

1993

1.96189

36.0967

92.063

1994

0.081467

39.6757

92.0277

1995

0.513826

29.8137

88.4952

1996

5.3328

37.7582

94.436

1997

0.877538

49.0027

92.2938

1998

1.53427

45.9879

94.5467

1999

2.48874

29.1083

90.0681

2000

2.07295

45.8186

90.2102

2001

1.91848

49.2512

95.746

2002

8.73106

45.5322

90.18

2003

5.48595

51.1772

95.2783

2004

9.55639

57.1429

89.9206

2005

2.92907

48.5362

96.9469