Trends in stream macroinvertebrates
Trends in macroinvertebrates (MCI) in rivers in the national monitoring network, 1990–2007
| Year | Rivers with lowest MCI [5th percentile] |
Rivers with median MCI | Rivers with highest MCI [95th percentile] |
|---|---|---|---|
| 1990 | 76 |
108 |
135 |
| 1991 | 77 |
107 |
126 |
| 1992 | 71 |
110 |
131 |
| 1993 | 74 |
107 |
136 |
| 1994 | 72 |
109 |
135 |
| 1995 | 70 |
111 |
139 |
| Change in sample preserving method - see note 4 | |||
| 1996 | 81 |
116 |
140 |
| 1997 | 79 |
109 |
136 |
| 1998 | 79 |
109 |
138 |
| 1999 | 75 |
107 |
132 |
| 2000 | 78 |
111 |
139 |
| 2001 | 80 |
111 |
141 |
| 2002 | 90 |
109 |
138 |
| 2003 | 86 |
110 |
137 |
| 2004 | 87 |
107 |
136 |
| 2005 | 80 |
108 |
140 |
2006 |
91 |
109 |
134 |
2007 |
82 |
107 |
129 |
Notes:
(1) Data is derived from 66 sites of the 77 that make up the national monitoring network.
(2) Higher MCI indicates better water quality.
(3) Hazen method used to calculate 5th and 95th percentiles.
(4) The break in the graph between 1995 and 1996 is where there was a change in preservative used, which appears to have altered the proportion of low scoring taxa found in samples. Results prior to 1996 should be compared with caution to results from 1996 onwards.
Data source: compiled by the Ministry for the Environment using data collected by National Institute of Water and Atmospheric Research (NIWA).
(1) Data is derived from 66 sites of the 77 that make up the national monitoring network.
(2) Higher MCI indicates better water quality.
(3) Hazen method used to calculate 5th and 95th percentiles.
(4) The break in the graph between 1995 and 1996 is where there was a change in preservative used, which appears to have altered the proportion of low scoring taxa found in samples. Results prior to 1996 should be compared with caution to results from 1996 onwards.
Data source: compiled by the Ministry for the Environment using data collected by National Institute of Water and Atmospheric Research (NIWA).
Trends in macroinvertebrates (%EPT) in rivers in the national monitoring network, 1989–2007
| Year |
Rivers with lowest %EPT |
Rivers with median %EPT |
Rivers with highest %EPT |
|---|---|---|---|
| 1989 | 0.51 |
37.36 |
82.45 |
1990 |
1.04 |
40.33 |
91.93 |
1991 |
1.95 |
50.91 |
92.35 |
1992 |
0.72 |
40.05 |
94.11 |
1993 |
1.96 |
36.10 |
92.06 |
1994 |
0.08 |
39.68 |
92.03 |
1995 |
0.51 |
29.81 |
88.50 |
| Change in sample preserving method - see note 5 | |||
1996 |
5.33 |
37.76 |
94.44 |
1997 |
0.88 |
49.00 |
92.29 |
1998 |
1.54 |
45.99 |
94.55 |
1999 |
2.50 |
29.32 |
90.07 |
2000 |
2.08 |
46.92 |
90.21 |
2001 |
1.92 |
49.83 |
95.75 |
2002 |
8.73 |
43.90 |
90.01 |
2003 |
5.46 |
50.21 |
95.31 |
2004 |
9.56 |
57.14 |
89.92 |
2005 |
2.93 |
48.54 |
96.95 |
| 2006 | 3.38 |
66.39 |
97.43 |
| 2007 | 7.48 |
51.51 |
87.78 |
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.
(3) Hazen method used to calculate 5th and 95th percentiles.
(4) Oxytheira sp. and Paraoxytheira sp., which are from the Trichoptera order, have been excluded from the %EPT calculation, as they are typically not sensitive to pollution.
(5) The break in the graph between 1995 and 1996 is where there was a change in preservative used, which appears to have altered the proportion of low scoring taxa found in samples. Results prior to 1996 should be compared with caution to results from 1996 onwards.
Data source: compiled by the Ministry for the Environment using data collected by NIWA.
(2) Higher %EPT indicates better water quality.
(3) Hazen method used to calculate 5th and 95th percentiles.
(4) Oxytheira sp. and Paraoxytheira sp., which are from the Trichoptera order, have been excluded from the %EPT calculation, as they are typically not sensitive to pollution.
(5) The break in the graph between 1995 and 1996 is where there was a change in preservative used, which appears to have altered the proportion of low scoring taxa found in samples. Results prior to 1996 should be compared with caution to results from 1996 onwards.
Data source: compiled by the Ministry for the Environment using data collected by NIWA.
This information has come from the latest state of the environment report, Environment New Zealand 2007.
This data comes from the National River Water Quality Network which is operated by NIWA with funding from the Foundation for Research, Science and Technology.
You can access the national network data for 2007, as well as more site information, in this spreadsheet.
Return to the macroinvertebrates in rivers page.
Last updated: March 2009
