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Figure 7. Year-by-year changes in regional percentiles for manganese (Mn) in groundwater. Total Mn concentrations (blue) used where dissolved Mn data were not available.

All Y axis scales in mg/L. Numbers above X axes show the number of sites at which median values could be calculated for the region and calendar year of interest. Horizontal lines on each graph represent the aesthetic Guideline Value (0.04 mg/L) and the health-related Maximum Acceptable Value (0.4 mg/L) specified in the DWSNZ and the Trigger Value for ecosystem protection (1.9 mg/L) defined in the ANZECC guidelines.

Figure 7. Year-by-year changes in regional percentiles for manganese (Mn) in groundwater

Figure 7. Year-by-year changes in regional percentiles for manganese (Mn) in groundwater

Figure 7. Year-by-year changes in regional percentiles for manganese (Mn) in groundwater

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 2 6.0E-02 6.0E-02 0.0600 0.06 0.06 0.1
1997 4 2.0E-03 7.6E-03 0.0300 0.12 0.27 0.3
1998 20 6.1E-04 2.0E-03 0.0315 0.09 0.22 0.3
1999 23 8.5E-04 2.8E-03 0.0180 0.06 0.20 0.3
2000 22 6.9E-04 1.8E-03 0.0208 0.08 0.19 0.2
2001 23 9.2E-04 2.0E-03 0.0225 0.06 0.16 0.2
2002 23 8.4E-04 2.0E-03 0.0225 0.06 0.14 0.2
2003 22 7.6E-04 2.3E-03 0.0114 0.06 0.17 0.2
2004 22 5.7E-04 2.6E-03 0.0221 0.06 0.15 0.2
2005 22 5.2E-04 2.8E-03 0.0257 0.07 0.18 0.2
2006 21 8.0E-04 3.6E-03 0.0200 0.06 0.18 0.2
2007 22 9.6E-04 4.5E-03 0.0233 0.07 0.17 0.2
2008 23 7.2E-04 6.0E-03 0.0250 0.06 0.16 0.2
Change in Percentile Value Over Time2   - - - - - -

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7b) Bay of Plenty Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 48 1.5E-04 0.001 0.055 0.25 2.05 9.2
1997 53 2.2E-04 0.001 0.030 0.31 3.24 15.4
1998 37 3.6E-05 0.001 0.030 0.44 1.71 12.7
1999 12 3.2E-03 0.010 0.030 0.16 0.53 0.5
2000 12 5.0E-04 0.002 0.028 0.21 0.50 0.5
2001 6 1.7E-03 0.007 0.027 0.18 0.45 0.5
2002 25 1.6E-04 0.001 0.017 0.22 1.59 5.2
2003 15 3.0E-03 0.004 0.029 0.49 1.48 2.9
2004 6 1.6E-03 0.005 0.054 0.18 0.41 0.5
2005 37 5.9E-04 0.003 0.011 0.28 1.03 4.3
2006 47 8.7E-04 0.003 0.017 0.38 2.34 9.6
2007 38 1.7E-04 0.001 0.008 0.27 0.98 3.4
2008 41 3.3E-04 0.001 0.011 0.28 1.11 8.8
Change in Percentile Value Over Time2   - - -0.002 - - -

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7c) Canterbury Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 9 0.004 0.008 0.019 0.080 0.126 0.15
1996 4 0.030 0.030 0.030 0.030 0.030 0.03
1997 9 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01
1998 9 0.010 0.010 0.010 0.010 0.010 0.01
1999 3 0.004 0.004 0.004 0.004 0.004 0.00
2000 3 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005
2001 3 0.006 0.006 0.006 0.006 0.006 0.01
2002 3 0.031 0.031 0.031 0.031 0.031 0.03
2003 256 0.000 0.000 0.008 0.035 0.314 3.40
2004 255 0.001 0.003 0.010 0.037 0.313 3.90
2005 273 0.000 0.000 0.009 0.043 0.345 3.40
2006 277 0.000 0.000 0.000 0.002 0.292 3.40
2007 276 0.000 0.000 0.000 0.002 0.180 2.80
2008 285 0.000 0.000 0.000 0.003 0.126 3.00
Change in Percentile Value Over Time2   -0.001 -0.001 - - - -

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7d) Data not available

(Figure 7e) Hawkes Bay Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 16 0.003 0.014 0.080 0.240 0.589 0.67
1996 6 0.007 0.038 0.060 0.270 0.507 0.53
1997 39 0.001 0.010 0.059 0.220 0.588 1.26
1998 43 0.002 0.008 0.059 0.238 0.595 1.30
1999 42 0.001 0.007 0.044 0.208 0.600 1.25
2000 40 0.001 0.006 0.050 0.241 0.576 1.30
2001 43 0.001 0.007 0.050 0.220 0.603 1.40
2002 38 0.002 0.009 0.056 0.189 0.831 1.23
2003 43 0.001 0.007 0.050 0.218 0.584 1.25
2004 41 0.002 0.007 0.056 0.275 0.579 1.33
2005 42 0.001 0.005 0.060 0.346 0.748 1.37
2006 43 0.001 0.004 0.053 0.373 0.662 1.45
2007 43 0.001 0.003 0.050 0.359 0.642 1.34
2008 43 0.001 0.007 0.056 0.335 0.623 1.40
Change in Percentile Value Over Time2 - 0.000 -0.001 - - - 0.02

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7f) Manawatu-Wanganui Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 2 0.252 0.300 0.590 1.15 1.83 2.00
1996 2 0.023 0.049 0.388 0.81 1.76 2.00
1997 2 0.025 0.053 0.358 0.94 1.70 2.00
1998 4 0.011 0.050 0.340 0.93 2.67 3.15
1999 4 0.008 0.051 0.215 0.74 1.18 3.05
2000 3 0.007 0.050 0.270 0.84 1.17 3.05
2001 3 0.007 0.074 0.260 0.82 1.27 2.90
2002 5 0.038 0.158 0.695 0.93 1.40 3.05
2003 3 0.061 0.165 0.710 0.92 1.72 3.00
2004 3 0.052 0.392 0.739 1.00 1.91 2.70
2005 2 0.253 0.607 0.760 0.99 2.20 2.79
2006 16 0.021 0.048 0.167 0.32 1.04 2.16
2007 2 0.586 0.685 0.888 0.98 2.14 2.52
2008 2 0.011 0.027 0.046 0.20 0.33 0.36
Change in Percentile Value Over Time2   - - - - - -

(Figure 7g) Marlborough Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 1 0.060 0.060 0.060 0.060 0.060 0.06
1998 4 0.015 0.015 0.015 0.015 0.015 0.02
1999 4 0.000 0.002 0.013 0.046 0.171 0.21
2000 3 0.016 0.024 0.043 0.099 0.200 0.23
2001 5 0.002 0.006 0.014 0.072 0.171 0.21
2002 4 0.004 0.009 0.036 0.073 0.155 0.18
2003 4 0.001 0.002 0.028 0.077 0.172 0.20
2004 6 0.002 0.004 0.030 0.067 0.162 0.21
2005 13 0.000 0.001 0.003 0.041 0.105 0.25
2006 6 0.002 0.005 0.029 0.066 0.148 0.19
2007 6 0.001 0.003 0.034 0.073 0.134 0.17
2008 6 0.009 0.015 0.043 0.072 0.164 0.21
Change in Percentile Value Over Time2   - - - - - -

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7h) Northland Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 1 0.060 0.060 0.060 0.060 0.060 0.06
1998 4 0.015 0.015 0.015 0.015 0.015 0.02
1999 4 0.000 0.002 0.013 0.046 0.171 0.21
2000 3 0.016 0.024 0.043 0.099 0.200 0.23
2001 5 0.002 0.006 0.014 0.072 0.171 0.21
2002 4 0.004 0.009 0.036 0.073 0.155 0.18
2003 4 0.001 0.002 0.028 0.077 0.172 0.20
2004 6 0.002 0.004 0.030 0.067 0.162 0.21
2005 13 0.000 0.001 0.003 0.041 0.105 0.25
2006 6 0.002 0.005 0.029 0.066 0.148 0.19
2007 6 0.001 0.003 0.034 0.073 0.134 0.17
2008 6 0.009 0.015 0.043 0.072 0.164 0.21
Change in Percentile Value Over Time2   - - - - - -

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7i) Otago Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 9 0.001 0.003 0.010 0.010 0.046 0.10
1997 9 0.006 0.007 0.010 0.010 0.014 0.02
1998 9 0.010 0.010 0.010 0.010 0.010 0.01
1999 9 0.005 0.005 0.005 0.005 0.008 0.01
2000 5 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005
2001 5 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005
2002 10 0.000 0.000 0.001 0.175 7.208 23.00
2003 10 0.000 0.000 0.002 0.128 0.375 0.45
2004 9 0.000 0.001 0.013 0.216 0.432 0.51
2005 10 0.000 0.000 0.000 0.019 0.375 0.48
2006 20 0.000 0.000 0.000 0.005 0.153 1.53
2007 24 0.000 0.000 0.001 0.026 0.607 2.15
2008 47 0.000 0.000 0.007 0.058 0.646 2.23
Change in Percentile Value Over Time2   -0.001 -0.001 - 0.005 0.169 0.77

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7j) Southland Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 6 6.6E-12 1.5E-09 0.000 0.00 0.69 1.2
1999 5 2.7E-05 1.3E-04 0.003 0.06 0.75 1.1
2000 4 2.5E-05 1.5E-04 0.006 0.05 0.69 1.0
2001 3 9.3E-07 1.3E-05 0.003 0.18 0.75 0.9
2002 4 3.9E-06 3.6E-05 0.005 0.14 0.85 1.1
2003 5 2.5E-07 3.2E-06 0.002 0.11 0.76 0.9
2004 4 4.9E-06 4.0E-05 0.005 0.07 0.71 1.0
2005 29 3.9E-05 2.9E-04 0.003 0.02 0.37 1.0
2006 25 7.3E-05 8.1E-04 0.002 0.01 0.23 1.5
2007 29 1.7E-04 1.0E-03 0.005 0.01 1.27 1.9
2008 27 5.0E-05 4.8E-04 0.001 0.02 0.21 1.5
Change in Percentile Value Over Time2   5.5E-06 6.4E-05 - - - -

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7k) Taranaki Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 2 0.003 0.030 0.050 1.660 3.64 4.80
1996 3 0.002 0.010 0.038 0.691 1.04 4.11
1997 2 0.000 0.001 0.010 0.745 1.38 2.20
1998 2 0.001 0.011 0.020 0.405 0.98 0.98
1999 2 0.000 0.006 0.009 0.559 0.94 0.94
2000 2 0.000 0.002 0.010 0.537 0.85 0.89
2001 2 0.000 0.000 0.006 0.740 0.88 0.88
2002 2 0.005 0.006 0.012 0.109 0.44 0.69
2003 2 0.005 0.005 0.007 0.020 0.48 0.72
2004 2 0.003 0.006 0.006 0.008 0.45 0.70
2005 2 0.005 0.005 0.006 0.010 0.45 0.69
2006 2 0.001 0.005 0.007 0.007 0.47 0.72
2007 2 0.005 0.007 0.008 0.019 0.03 0.03
2008 2 0.008 0.019 0.041 0.069 0.34 0.48
Change in Percentile Value Over Time2   - - -0.001 -0.074 -0.09 -0.11

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7l) Tasman Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 10 4.5E-05 1.5E-04 0.0064 0.14 1.47 2.5
1997 10 2.2E-06 2.9E-05 0.0051 0.09 1.57 2.6
1998 9 8.4E-10 3.1E-08 0.0000 0.02 1.66 2.6
1999 10 6.3E-07 1.7E-05 0.0011 0.12 1.55 2.6
2000 10 1.9E-07 4.9E-06 0.0003 0.17 1.51 2.5
2001 10 7.9E-05 5.3E-04 0.0090 0.23 1.43 2.3
2002 13 9.3E-06 4.1E-05 0.0020 0.02 1.18 2.5
2003 16 6.7E-05 1.6E-04 0.0048 0.02 0.93 2.7
2004 16 7.7E-05 5.8E-04 0.0070 0.02 0.87 2.6
2005 16 2.0E-04 1.4E-03 0.0058 0.02 0.88 2.6
2006 16 7.0E-07 4.8E-05 0.0020 0.02 0.89 2.6
2007 16 1.8E-05 1.1E-04 0.0055 0.02 0.93 2.6
2008 16 8.0E-06 2.9E-05 0.0015 0.03 1.02 2.6
Change in Percentile Value Over Time2   - - - - -0.070 -

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7m) Waikato Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 3 0.060 0.060 0.060 0.060 0.060 0.06
1997 6 0.000 0.000 0.000 0.003 0.043 0.06
1998 6 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01
1999 7 0.000 0.000 0.001 0.005 0.015 0.02
2000 7 0.020 0.020 0.020 0.020 0.020 0.02
2001 7 0.010 0.010 0.010 0.010 0.010 0.01
2002 18 0.000 0.000 0.001 0.007 0.234 1.04
2003 7 0.001 0.001 0.002 0.005 0.008 0.01
2004 0            
2005 4 0.056 0.080 0.366 0.420 0.467 0.48
2006 98 0.000 0.000 0.001 0.009 0.238 4.40
2007 14 0.000 0.001 0.003 0.013 0.358 0.69
2008 84 0.000 0.000 0.001 0.009 0.458 3.00
Change in Percentile Value Over Time2   - - - - - -

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7n) Wellington Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 9 2.7E-04 1.3E-03 0.0350 0.06 1.33 1.8
1996 22 1.4E-05 1.0E-04 0.0013 0.04 0.76 1.8
1997 31 6.7E-05 3.9E-04 0.0034 0.05 0.85 1.7
1998 49 1.1E-03 4.6E-03 0.0300 0.39 0.95 1.6
1999 49 7.3E-04 4.1E-03 0.0435 0.43 1.01 1.6
2000 50 1.7E-03 5.3E-03 0.0300 0.46 0.99 1.6
2001 47 8.7E-04 3.6E-03 0.0400 0.43 1.07 1.5
2002 47 1.4E-03 4.7E-03 0.0325 0.44 1.14 1.5
2003 48 1.1E-04 1.0E-03 0.0141 0.40 0.85 1.4
2004 60 2.6E-07 3.1E-06 0.0001 0.00 0.56 1.5
2005 64 7.2E-08 1.3E-06 0.0001 0.00 0.42 1.6
2006 65 1.4E-09 7.8E-08 0.0000 0.00 0.49 1.7
2007 65 4.0E-09 2.0E-07 0.0000 0.01 0.45 1.7
2008 63 1.7E-10 1.5E-08 0.0000 0.00 0.51 1.4
Change in Percentile Value Over Time2   -2.1E-05 -1.1E-04 -0.0026 - -0.044 -0.018

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.

(Figure 7o) West Coast Region calculated percentiles and maximum values for manganese in groundwater (in mg/L), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 6 0.000 0.001 0.006 0.018 0.05 0.06
1999 7 0.001 0.003 0.005 0.012 0.04 0.05
2000 7 0.003 0.007 0.008 0.015 0.04 0.05
2001 7 0.002 0.004 0.008 0.024 0.05 0.05
2002 6 0.001 0.002 0.006 0.018 0.03 0.03
2003 7 0.004 0.006 0.019 0.027 0.06 0.07
2004 8 0.000 0.001 0.004 0.027 0.06 0.07
2005 8 0.001 0.002 0.010 0.029 0.07 0.10
2006 8 0.000 0.000 0.003 0.022 0.10 0.15
2007 8 0.000 0.000 0.002 0.011 0.42 0.63
2008 8 0.000 0.000 0.005 0.013 0.22 0.33
Change in Percentile Value Over Time2   -0.0001 -0.0003 - - 0.01 0.02

1 Total number of sites for which a median value could be calculated (i.e. parameter had been measured at least once at the site in question within the calender year of interest).

2 Trend tests performed on calculated percentile values for the years 1995 to 2008. A null value (-) indicates that no significant trend was detected at the 95% confidence interval. Numbers are in units per year and indicate significant trends. Negative numbers indicate a decreasing trend.