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Figure 8. Year-by-year changes in regional percentiles for electrical conductivity in groundwater. All Y axis scales in μS/cm. Numbers above X axes show the number of sites at which median values could be calculated for the region and calendar year of interest.

Figure 8. Year-by-year changes in regional percentiles for electrical conductivity in groundwater

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(Figure 8a) Auckland Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	0
1996	2	333	423	535	648	738	760
1997	3	212	260	355	491	638	675
1998	21	202	254	294	433	662	3790
1999	9	164	229	288	583	2009	3110
2000	9	196	223	285	395	620	750
2001	21	173	221	280	410	662	725
2002	22	166	220	280	401	618	740
2003	21	165	224	308	426	711	3570
2004	18	216	282	388	466	743	3530
2005	22	208	274	333	443	726	761
2006	21	188	266	314	460	715	745
2007	22	173	267	307	441	711	771
2008	23	149	223	325	443	663	859
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 8b) Bay of Plenty Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	46	90	140	234	497	1153	2240
1996	53	83	117	239	477	905	1440
1997	59	86	114	226	465	988	27700
1998	58	90	115	211	440	1094	1980
1999	15	84	173	340	400	1135	1796
2000	12	99	116	287	363	852	878
2001	12	91	100	275	367	840	877
2002	41	94	169	241	518	1030	2752
2003	22	81	102	240	363	901	927
2004	49	86	114	208	427	1242	27300
2005	45	88	138	233	490	2030	27300
2006	53	86	105	206	421	1247	28000
2007	44	79	102	195	391	1167	2023
2008	46	82	110	212	408	1586	27860
Change in Percentile Value Over Time²		-	-	-3.3	-	-	-

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).

(Figure 8c) Canterbury Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	182	83	113	145	190	329	750
1996	211	86	121	160	200	332	677
1997	241	86	121	162	200	329	1300
1998	251	86	120	162	200	334	680
1999	265	90	128	170	220	409	1100
2000	271	100	157	184	239	533	1278
2001	253	91	144	185	244	546	875
2002	277	96	140	190	259	578	980
2003	256	110	160	210	310	704	6000
2004	262	98	150	200	270	625	2665
2005	272	89	139	180	240	444	4500
2006	269	100	150	190	250	448	1300
2007	274	100	140	180	240	419	1400
2008	278	110	150	200	255	453	2130
Change in Percentile Value Over Time²		1.6	2.7	3.5	5.0	11.7	87.5

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).

(Figure 8d) Data not available

(Figure 8e) Hawkes Bay Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	22	140	170	230	290	508	725
1996	8	165	175	223	280	475	525
1997	41	116	170	241	360	1432	2548
1998	44	107	160	242	454	1351	2614
1999	43	117	161	270	428	1475	2603
2000	42	132	170	247	467	1608	2731
2001	44	122	167	242	480	1256	2631
2002	40	126	164	256	522	1380	2595
2003	44	129	169	270	516	1234	2625
2004	36	125	163	237	464	1554	2593
2005	42	118	168	261	467	1271	2583
2006	42	115	168	253	482	1292	2607
2007	45	116	171	254	536	1278	2680
2008	44	127	179	274	546	1218	2655
Change in Percentile Value Over Time²		-	-	2.8	16.8	-	-

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).

(Figure 8f) Manawatu-Wanganui Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	7	117	298	340	497	681	717
1996	8	117	302	347	504	638	660
1997	8	137	305	347	506	661	764
1998	22	116	223	330	525	832	6215
1999	27	108	229	322	469	702	5825
2000	19	97	201	323	517	818	6115
2001	18	130	278	385	543	860	6135
2002	8	254	444	520	590	1024	1155
2003	11	274	420	530	640	892	1110
2004	3	270	472	501	620	985	1190
2005	3	249	474	510	580	858	990
2006	3	267	361	462	588	5860	5930
2007	1	492	492	492	492	492	492
2008	2	288	306	328	366	396	403
Change in Percentile Value Over Time²		18.8	15.3	-	-	-	-

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).

(Figure 8g) Marlborough Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	0
1996	0
1997	2	105	163	235	308	366	380
1998	5	73	93	190	258	286	295
1999	6	88	135	150	243	283	300
2000	7	104	150	160	260	466	590
2001	12	70	110	195	310	473	570
2002	8	135	204	285	369	402	411
2003	8	130	214	308	378	415	420
2004	5	90	182	330	363	410	422
2005	20	74	121	189	321	457	615
2006	19	72	126	200	271	533	684
2007	12	78	128	155	270	601	715
2008	22	70	129	179	274	654	750
Change in Percentile Value Over Time²		-	-	-	-	26.0	33.6

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).

(Figure 8h) Northland Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	4	452	545	559	569	914	1000
1996	6	254	374	458	569	661	697
1997	3	362	475	526	534	544	547
1998	3	410	476	517	532	538	539
1999	7	138	244	348	529	615	680
2000	6	134	284	341	460	1401	1871
2001	10	146	382	432	588	829	1175
2002	13	150	381	548	618	1893	5183
2003	25	112	211	458	573	1345	4449
2004	33	115	282	453	555	986	4419
2005	32	144	307	491	591	1098	3965
2006	33	142	346	526	709	2166	4216
2007	38	139	255	495	674	1911	4499
2008	39	146	242	484	688	2398	4358
Change in Percentile Value Over Time²		-0.001	-	-	0.01	0.08	0.58

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).

(Figure 8i) Otago Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median va

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	30	107	208	323	745	1434	1552
1996	36	86	180	482	1187	1909	2020
1997	52	3	199	369	1132	2083	2590
1998	79	91	178	343	1042	2015	4580
1999	82	101	167	338	1008	2469	9160
2000	94	91	157	276	853	4809	113716
2001	99	75	159	256	584	1423	2113
2002	93	82	150	268	565	1569	2220
2003	91	86	155	257	583	1460	2160
2004	90	85	160	246	498	1445	2085
2005	91	90	154	220	518	1435	1860
2006	91	70	129	182	390	1315	2035
2007	89	74	134	195	367	1532	2510
2008	71	91	169	258	447	1730	88571
Change in Percentile Value Over Time²		-	-4.6	-16.2	-62.3	-	-

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).

(Figure 8j) Southland Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	0
1996	0
1997	0
1998	7	164	191	208	235	250	250
1999	5	152	166	200	215	246	255
2000	19	142	178	230	258	514	825
2001	23	115	177	224	269	389	516
2002	27	133	166	230	275	513	765
2003	28	119	161	208	265	498	707
2004	24	131	158	224	270	412	510
2005	30	100	155	201	257	451	547
2006	30	126	168	212	256	310	508
2007	34	114	158	212	269	402	489
2008	47	133	174	225	272	422	834
Change in Percentile Value Over Time²		-4.0	-	-	-	-	-

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).

(Figure 8k) Taranaki Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	64	142	286	361	698	1267	1920
1996	57	108	299	405	764	1245	1930
1997	62	111	280	359	680	1067	1890
1998	70	111	282	351	669	1301	2830
1999	56	144	275	328	628	1449	2845
2000	41	116	282	432	747	1320	2560
2001	45	151	264	365	712	1075	1725
2002	51	149	264	366	716	1668	4990
2003	34	175	264	365	798	1262	25000
2004	33	133	242	368	742	969	6130
2005	49	174	254	323	590	1010	1370
2006	57	118	223	307	491	971	3760
2007	52	147	253	377	714	2781	3430
2008	44	10	245	566	823	2950	4730
Change in Percentile Value Over Time²		-	-3.7	-	-	-	-

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).

(Figure 8l) Tasman Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	8	220	228	328	408	611	660
1996	10	210	220	265	350	592	650
1997	10	186	211	258	344	549	580
1998	16	165	195	215	286	532	650
1999	10	200	211	260	351	614	720
2000	10	212	223	275	359	605	690
2001	10	205	238	275	348	531	565
2002	16	140	207	223	298	491	614
2003	16	149	193	220	301	498	640
2004	16	150	209	225	310	464	518
2005	16	148	208	235	325	492	566
2006	16	153	192	222	326	408	439
2007	16	144	197	223	313	465	550
2008	16	141	198	224	320	491	673
Change in Percentile Value Over Time²		-5.7	-2.0	-4.1	-3.5	-12.0	-

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).

(Figure 8m) Waikato Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	49	88	148	209	261	342	412
1996	53	79	130	187	244	393	425
1997	54	91	139	211	264	373	529
1998	42	117	170	231	300	447	600
1999	38	106	163	219	247	391	630
2000	34	113	168	220	270	408	620
2001	43	88	133	214	267	401	625
2002	62	67	123	178	253	367	645
2003	99	81	129	193	270	419	660
2004	100	76	132	194	284	411	671
2005	107	74	125	196	260	406	622
2006	113	74	121	184	259	411	642
2007	110	74	118	178	239	384	1300
2008	115	79	126	199	270	443	6200
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).

(Figure 8n) Wellington Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	16	90	128	184	266	351	364
1996	23	100	130	178	272	344	350
1997	24	100	120	189	272	502	674
1998	25	100	133	191	265	482	644
1999	25	94	133	182	264	478	710
2000	25	106	130	181	268	481	638
2001	25	106	134	199	260	466	771
2002	25	112	140	195	267	474	639
2003	49	101	163	232	333	654	1440
2004	51	108	166	226	334	738	1200
2005	71	96	140	198	306	717	1370
2006	70	95	139	198	318	722	1480
2007	69	95	139	198	320	712	1355
2008	69	94	140	190	325	663	1350
Change in Percentile Value Over Time²		-	1.1	-	4.8	28.1	87.0

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).

(Figure 8o) West Coast Region calculated percentiles and maximum values for electric conductivity in groundwater (in μS/cm), based on site-specific median values.

Year	n¹	Percentile					Max
Year	n¹	5th	25th	50th	75th	95th	Max
1995	0
1996	0
1997	0
1998	6	72	79	93	108	110	110
1999	7	63	66	75	84	86	86
2000	7	55	62	70	83	88	88
2001	7	65	78	99	103	108	109
2002	4	87	96	101	103	104	104
2003	7	80	93	104	114	145	159
2004	7	51	61	72	75	78	79
2005	8	61	81	97	105	111	111
2006	8	61	66	69	74	84	88
2007	8	63	68	82	95	117	129
2008	8	70	80	90	106	123	129
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).

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