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Figure 5. Year-by-year changes in regional percentiles for E. coli in groundwater, based on site-specific median values.

Faecal colifom concentrations (blue) or total coliform concentrations (green) used where E. coli data were not available. All Y axis scales in cfu/100 ml. 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 health-related Maximum Acceptable Value (1 cfu/100 ml) specified in the DWSNZ and the Trigger Value for livestock consumption (100 cfu/100 ml) defined in the ANZECC guidelines.

Figure 5. Year-by-year changes in regional percentiles for E. coli in groundwater, based on site-specific median values

Figure 5. Year-by-year changes in regional percentiles for E. coli in groundwater, based on site-specific median values

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 0            
1999 0            
2000 0            
2001 0            
2002 0            
2003 0            
2004 0            
2005 18 2.3E-09 3.0E-07 0.0002 0.06 43.80 190
2006 21 5.0E-13 6.1E-10 0.0000 0.03 150.00 300
2007 22 9.0E-08 8.2E-06 0.0021 1.55 124.53 135
2008 23 2.9E-06 1.3E-04 0.0127 1.49 37.60 555
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 5b) Bay of Plenty Region calculated percentiles and maximum values for faecal coliforms in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 9 3.0 3.0 3.0 3.0 3.0 3.0
1996 12 6.1E-08 2.8E-06 4.5E-04 0.3 10.1 20.0
1997 12 0.1 0.2 0.4 1.0 1.5 2.0
1998 13 1.0 1.0 1.0 1.0 1.0 1.0
1999 0            
2000 1 <1 <1 <1 <1 <1 <1
2001 0            
2002 9 6.0 6.0 6.0 6.0 6.0 6.0
2003 5 13.0 13.0 13.0 13.0 13.0 13.0
2004 10 3.6E-02 0.3 1.0 18.3 67.6 91.0
2005 10 1.2E-07 6.1E-06 7.8E-04 0.8 23.5 41.0
2006 8 <1 <1 <1 <1 <1 <1
2007 12 1.8E-07 8.0E-06 1.2E-03 0.2 19.8 33.0
2008 6 2.0 2.0 2.0 2.0 2.0 2.0
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 5c) Canterbury Region calculated percentiles and maximum values for E. coli in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 0            
1999 227 0.000 0.000 0.003 0.59 5.0 670
2000 236 0.049 0.267 1.000 3.28 25.4 260
2001 245 0.004 0.036 0.529 1.66 17.7 2400
2002 247 0.005 0.055 0.783 3.60 45.6 2400
2003 243 0.517 1.731 3.421 8.23 25.5 2400
2004 241 0.001 0.010 0.204 1.50 15.6 1300
2005 255 0.009 0.081 1.000 3.25 38.4 2400
2006 254 0.005 0.056 0.883 2.21 12.0 501
2007 275 0.000 0.004 0.227 1.48 12.1 1700
2008 284 0.000 0.009 0.637 3.97 23.9 2400
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 5d) Data not available

(Figure 5e) Hawkes Bay Region calculated percentiles and maximum values for E. coli (for years 2005-2008) or faecal coliforms (for years 1997-2004) in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 33 0.001 0.001 0.001 0.01 4.0 16
1998 34 0.001 0.001 0.000 0.06 4.0 15
1999 33 0.001 0.001 0.154 1.88 95.4 150
2000 33 0.001 0.003 0.038 1.00 6.8 31
2001 34 0.001 0.001 0.001 0.01 2.5 147
2002 33 0.001 0.001 0.001 0.01 4.0 96
2003 34 0.001 0.001 0.131 1.44 15.0 250
2004 33 0.001 0.001 0.001 0.02 4.0 34
2005 33 1.867 1.946 2.042 2.19 2.3 22
2006 34 0.016 0.040 0.131 0.43 1.0 2
2007 35 0.000 0.000 0.000 0.00 61.5 1300
2008 34 0.000 0.002 0.029 0.38 1.2 22
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 5f) Data not available

(Figure 5g) Marlborough Region calculated percentiles and maximum values for E. coli in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 0 8.760 8.760 8.760 8.76 8.8 9
1999 0            
2000 0            
2001 2 2.000 2.000 2.000 2.00 2.0 2
2002 0            
2003 0            
2004 0            
2005 5 1.000 1.000 1.000 1.00 1.0 1
2006 6 <1 <1 <1 <1 <1 <1
2007 0            
2008 6 0.000 0.001 0.010 0.12 3.6 9
Change in Percentile Value Over Time2   -0.42 -0.42 -0.42 -0.40 -0.40 -0.28

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 5h) Northland Region calculated percentiles and maximum values for E. coli in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 0            
1999 0            
2000 0            
2001 3 4.050 8.250 16.00 100.3 288.1 335
2002 7 7.8E-10 2.8E-08 0.03 0.8 340.6 616
2003 19 3.2E-05 4.5E-04 0.03 1.8 811.3 2000
2004 27 0.006 0.018 0.55 6.5 22.4 345
2005 27 1.5E-04 0.002 0.56 3.0 29.3 179
2006 29 0.026 0.084 1.00 2.3 16.5 44
2007 32 0.012 0.076 1.00 3.5 313.8 1210
2008 32 0.003 0.019 1.00 3.0 62.9 2419
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 5i) Otago Region calculated percentiles and maximum values for E. coli in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 2 2.000 2.000 2.00 2.00 2.0 2
1999 5 0.679 2.000 3.00 13.25 845.4 1200
2000 17 0.002 0.020 1.00 25.50 156.8 330
2001 27 0.000 0.000 0.03 13.75 216.8 2414
2002 21 0.003 0.018 0.22 3.00 47.4 300
2003 27 0.000 0.000 0.00 0.77 15.8 870
2004 21 0.036 0.133 1.00 3.25 19.1 45
2005 21 0.000 0.002 0.03 1.50 19.4 190
2006 22 0.000 0.003 0.06 4.25 34.7 102
2007 28 0.005 0.028 0.19 1.62 12.0 16
2008 27 1.000 1.000 1.00 1.00 1.0 1
Change in Percentile Value Over Time2   - - - - - -51

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 5j) Southland region percentiles and maximum values for E. coli in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 0            
1999 0            
2000 0            
2001 13 1.7E-06 4.6E-05 0.003 0.24 2.7 18
2002 15 1.3E-07 1.2E-05 0.004 1.03 20.7 650
2003 19 1.8E-05 3.8E-04 0.016 1.00 11.1 180
2004 16 1.3E-03 6.7E-03 0.074 1.00 2.8 11
2005 22 1.6E-03 1.5E-02 1.000 1.00 39.4 2400
2006 19 2.7E-04 2.5E-03 0.039 0.72 4.1 10
2007 21 5.5E-01 1.5E+00 2.276 3.50 5.0 14
2008 30 2.6E-03 2.2E-02 0.345 1.11 9.4 517
Change in Percentile Value Over Time2   0.0004 0.004 0.058 - - -

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 5k) Taranaki Region calculated percentiles and maximum values for E. coli in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 1 <1 <1 <1 <1 <1 <1
1997 3 0.34 1.51 2.5 24 75 88
1998 3 1.34 6.04 19.5 171 506 590
1999 0            
2000 0            
2001 0            
2002 0            
2003 0            
2004 10 11.00 11.00 11.0 11 11 11
2005 0            
2006 60 0.32 0.75 6.0 19 40 54
2007 59 0.00 0.02 1.0 38 423 515
2008 0            
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 5l) Data not available

(Figure 5m) Waikato Region calculated percentiles and maximum values for E. coli in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 13 0.014 0.069 0.50 5.00 29.8 34
1999 0            
2000 0            
2001 0            
2002 0            
2003 1 <1 <1 <1 <1 <1 <1
2004 43 1.4E-04 1.8E-03 0.04 1.00 11.7 32
2005 15 0.003 0.024 0.58 1.75 40.9 190
2006 4 <1 <1 <1 <1 <1 <1
2007 1 2.000 2.000 2.00 2.00 2.0 2
2008 42 4.9E-10 1.2E-07 0.00 0.11 15.8 1600
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 5n) Wellington Region calculated percentiles and maximum values for E. coli (for years 2004-2008) or total coliforms (for years 1995-2003) in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 3 1.3E+00 2.5E+00 4.0000 8.50 12.1 13
1996 4 1.0E+00 1.0E+00 33.0000 186.00 278.0 301
1997 3 3.1E+00 1.2E+01 19.5000 24.38 25.3 26
1998 9 1.0E+00 1.0E+00 5.0000 32.50 150.3 184
1999 12 7.3E-02 1.0E+00 2.0000 8.00 148.1 319
2000 11 1.0E+00 1.0E+00 3.0000 83.00 330.2 416
2001 9 1.5E+00 3.0E+00 8.0000 35.00 199.5 262
2002 14 3.4E-02 1.2E-01 1.0000 3.00 23.8 35
2003 42 2.0E-12 9.7E-10 0.0000 0.01 3.6 12
2004 52 2.9E-07 1.5E-05 0.0022 0.31 2.3 31
2005 59 2.1E-23 3.4E-18 0.0000 0.00 8.8 100
2006 58 1.4E-02 5.0E-02 0.2789 1.00 3.0 5
2007 42 7.8E-16 2.3E-12 0.0000 0.00 82.9 840
2008 38 5.0E-07 4.8E-05 0.0143 0.91 10.2 301
Change in Percentile Value Over Time2   -0.100 -0.136 -0.500 -1.67 - -

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 5o) West Coast Region calculated percentiles and maximum values for E. coli in groundwater (in cfu/100 ml), based on site-specific median values.

Parameter n1 Percentile Max
5th 25th 50th 75th 95th
1995 0            
1996 0            
1997 0            
1998 0            
1999 0            
2000 5 5.0 5.0 5.0 5 5 5
2001 7 5.0 5.0 5.0 5 5 5
2002 6 0.4 2.0 5.0 5 159 210
2003 7 3.0 3.3 5.0 5 5 5
2004 7 0.1 0.2 1.0 3 6 6
2005 8 4.1 4.8 5.0 5 5 5
2006 8 1.0 1.3 5.0 5 8 11
2007 8 0.0 0.0 0.3 1 15 23
2008 8 1.0 1.0 1.0 1 1 1
Change in Percentile Value Over Time2   - -0.6 - - - -

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.