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Visual clarity trends in rivers

Visual clarity trends in rivers in the National River Water Quality Network, 1989–2007 

  Rivers with lowest concentrations
(5th percentile)
(m)		 Median rivers (50th percentile)
(m)		 Rivers with highest concentrations
(95th percentile)
(m)
1989
0.28
1.32
6.73
1990
0.25
1.26
5.31
1991
0.38
1.56
5.83
1992
0.41
1.37
5.80
1993
0.57
1.67
6.43
1994
0.24
1.24
6.06
1995
0.22
1.12
4.16
1996
0.19
1.05
5.73
1997
0.39
1.35
6.22
1998
0.40
1.60
5.82
1999
0.42
1.66
6.94
2000
0.36
1.20
6.11
2001
0.49
1.78
6.55
2002
0.34
1.33
5.89
2003
0.33
1.65
5.85
2004
0.21
1.45
7.33
2005
0.48
1.86
6.81
2006
0.36
1.37
5.86
2007
0.51
2.01
6.00
Data source: compiled by the Ministry for the Environment using data collected by the National Institute of Water and Atmospheric Research (NIWA).

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.

You can access the results of trend analysis on the national network data from 1989 to 2007 in this spreadsheet.

 

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Last updated: 10 August 2009