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SELWYN · PUBLISHED NITRATE RESULTS

Selwyn's drinking water nitrate results, bore by bore

This is every nitrate result Selwyn Water has published for its drinking-water sources, in one place, with dates. There are 1,742 of them, from 50 bores and intakes across 26 supplies, sampled between 9 Jan 2023 and 21 Aug 2026. None is at or above New Zealand's legal limit, and the highest is 67.3% of it. Find your supply below to see each source's readings and their share of that limit.

Published supplier data
Read from Selwyn Water Limited's drinking water quality testing page and its Annual Chemical Analysis Report - 2026
Figures read 13 Oct 2026 · 1,742 nitrate-nitrogen results at the source, 9 Jan 2023 to 21 Aug 2026 · No Brainer Water Co. is independent of Selwyn Water
Find your supply Download every reading (CSV)

THE DISTRICT PICTURE

No result at the limit, 100 at half of it or more.

New Zealand's legal limit for nitrate in drinking water is 11.3 mg/L when it is measured as nitrate-nitrogen, which is the same limit as 50 mg/L measured as nitrate. Selwyn Water prints its results as nitrate-nitrogen in g/m3, and one g/m3 is the same as one mg/L, so every share on this page is the reading divided by 11.3. The readings are taken at the source, the bore or the intake, and are not kitchen-tap samples.

0
Results at or above the legal limit
Out of 1,742 published results from 50 sources, 9 Jan 2023 to 21 Aug 2026.
7.6g/m3
Highest published result
Rolleston's Illinois Bore (G02009) on 16 May 2025, which is 67.3% of the limit. The published table notes it as a backup source, mixed with other sources if used.
100
Results at half the limit or more
All at five of the 50 sources. Three sources, one each in Rolleston, Kirwee and Darfield, hold 98 of them.

Where those 100 results are

Source At half the limit or more Highest published Latest
Illinois BoreG02009 · Rolleston40 of 4527 Jan 2023 to 18 Jun 20267.6 g/m316 May 2025 · 67.3%5.8 g/m318 Jun 2026 · 51.3%
Kirwee BoreG00725 · Kirwee34 of 4615 Sep 2023 to 19 Aug 20266.26 g/m315 May 2024 and 15 Jan 2025 · 55.4%5.91 g/m319 Aug 2026 · 52.3%
SH73 Bore 1G01961-2 · Darfield24 of 4710 May 2023 to 19 Aug 20266.3 g/m310 Apr 2024 · 55.8%5.78 g/m319 Aug 2026 · 51.2%
Dunsandel BoreG00726 · Dunsandel1 of 4615 Sep 2023 only6.6 g/m315 Sep 2023 · 58.4%3.32 g/m319 Aug 2026 · 29.4%
Te Pirita BoreG01169 · Te Pirita1 of 4117 May 2024 only5.66 g/m317 May 2024 · 50.1%4.51 g/m311 Aug 2026 · 39.9%

Half the limit is 5.65 g/m3. Counts follow the bands in Selwyn Water's published table. Illinois Bore carries this printed note in that table: Backup source only. Mixed with other sources if used. Its latest published result is dated 18 Jun 2026, and the other Rolleston bores run to 17 Aug 2026. Selwyn Water says it tests supplies serving more than 500 people monthly and smaller supplies annually, and tests any supply monthly once results exceed 50% of the limit.

SUPPLY BY SUPPLY

Find your supply

All 26 supplies with published nitrate results, highest latest reading first. Where a supply has more than one source, the latest reading shown is the highest of its sources' latest readings, and that source is named. Choose a supply to see every source.

Supply Latest reading Share of the legal limit Highest published reading Results
Kirwee1 source5.91 g/m319 Aug 2026 · Kirwee Bore (G00725)52.3%
6.26 g/m315 May 2024 and 15 Jan 2025 · Kirwee Bore (G00725) · 55.4%469 Jan 2023 to 19 Aug 2026
Rolleston12 sources5.8 g/m318 Jun 2026 · Illinois Bore (G02009), printed as a backup sourceOther sources: highest latest 4.78 g/m3 at Overbury Bore (G01113), 17 Aug 2026, 42.3%51.3%
7.6 g/m316 May 2025 · Illinois Bore (G02009) · 67.3%46927 Jan 2023 to 17 Aug 2026
Darfield2 sources5.78 g/m319 Aug 2026 · SH73 Bore 1 (G01961-2)51.2%
6.3 g/m310 Apr 2024 · SH73 Bore 1 (G01961-2) · 55.8%9110 Jan 2023 to 19 Aug 2026
Te Pirita1 source4.51 g/m311 Aug 2026 · Te Pirita Bore (G01169)39.9%
5.66 g/m317 May 2024 · Te Pirita Bore (G01169) · 50.1%4126 Apr 2023 to 11 Aug 2026
Dunsandel1 source3.32 g/m319 Aug 2026 · Dunsandel Bore (G00726)29.4%
6.6 g/m315 Sep 2023 · Dunsandel Bore (G00726) · 58.4%469 Jan 2023 to 19 Aug 2026
Southbridge1 source3.32 g/m318 Aug 2026 · St John Bore (G03053)29.4%
3.67 g/m318 Mar 2026 · St John Bore (G03053) · 32.5%4727 Jan 2023 to 18 Aug 2026
Sheffield2 sources2.78 g/m319 Aug 2026 · Sheffield Bore (G00820)24.6%
3.97 g/m316 Jun 2025 · Sheffield Bore (G00820) · 35.1%679 Jan 2023 to 19 Aug 2026
Jowers Road1 source2.47 g/m314 May 2026 · Jowers Bore (G00671)21.9%
2.83 g/m311 Apr 2024 · Jowers Bore (G00671) · 25.0%426 Apr 2023 to 14 May 2026
Greater West Melton5 sources2.39 g/m319 Aug 2026 · Edendale Bore (G02166)21.2%
4.19 g/m313 Sep 2023 · Elizabeth Allen Bore (G01957) · 37.1%2309 Jan 2023 to 19 Aug 2026
Springston1 source2.06 g/m318 Aug 2026 · Springston Bore (G01794)18.2%
2.09 g/m317 Jul 2026 · Springston Bore (G01794) · 18.5%4727 Jan 2023 to 18 Aug 2026
Lincoln4 sources1.91 g/m321 Aug 2026 · Kakahi Bore (G03127)16.9%
2.02 g/m328 Aug 2024 · Marion Pl Bore (G11199) · 17.9%16727 Jan 2023 to 21 Aug 2026
Springfield1 source1.53 g/m318 Aug 2026 · Springfield Intake (S10058)13.5%
4.56 g/m39 Aug 2023 · Springfield Intake (S10058) · 40.4%489 Jan 2023 to 18 Aug 2026
Leeston2 sources1.48 g/m318 Aug 2026 · Leeston Dunsandel Bore (G03119)13.1%
1.72 g/m38 Apr 2024 · Leeston Dunsandel Bore (G03119) · 15.2%9427 Jan 2023 to 18 Aug 2026
Taumutu1 source1.47 g/m314 May 2026 · Taumutu Bore (G00680)13.0%
1.48 g/m311 Mar 2025 · Taumutu Bore (G00680) · 13.1%426 Apr 2023 to 14 May 2026
Claremont1 source1.3 g/m325 May 2026 · Claremont Bore (G01673)11.5%
1.3 g/m325 May 2026 · Claremont Bore (G01673) · 11.5%426 Apr 2023 to 25 May 2026
Prebbleton4 sources0.78 g/m321 Aug 2026 · Tosswill Bore 2 (G00463)6.9%
0.83 g/m316 Apr 2025 and 16 Dec 2025 · Tosswill Bore 2 (G00463) · 7.3%16827 Jan 2023 to 21 Aug 2026
Rakaia Huts1 source0.76 g/m325 May 2026 · Rakaia Huts Bore (G00668)6.7%
0.77 g/m328 Mar 2025 · Rakaia Huts Bore (G00668) · 6.8%426 Apr 2023 to 25 May 2026
Hartleys Road1 source0.51 g/m321 Aug 2026 · Hartley's Intake (S00828)4.5%
1.21 g/m314 Jul 2026 · Hartley's Intake (S00828) · 10.7%479 Jan 2023 to 21 Aug 2026
Dalethorpe1 source0.44 g/m326 May 2026 · Dalethorpe Intake (S00827)3.9%
0.83 g/m324 Apr 2023 · Dalethorpe Intake (S00827) · 7.3%424 Apr 2023 to 26 May 2026
Hororātā1 source0.33 g/m321 Aug 2026 · Hororata Intake (G00822)2.9%
0.8 g/m315 Aug 2024 · Hororata Intake (G00822) · 7.1%479 Jan 2023 to 21 Aug 2026
Tai Tapu1 source0.33 g/m321 Aug 2026 · Tai Tapu Bore (G00675)2.9%
0.37 g/m315 Aug 2025 · Tai Tapu Bore (G00675) · 3.3%4727 Jan 2023 to 21 Aug 2026
Upper Selwyn Huts1 source0.22 g/m314 May 2026 · Upper Selwyn Huts Bore (G01315)1.9%
0.26 g/m311 Apr 2024 · Upper Selwyn Huts Bore (G01315) · 2.3%426 Apr 2023 to 14 May 2026
Castle Hill1 source0.06 g/m325 May 2026 · Castle Hill Intake (S00579)0.5%
0.1 g/m324 Apr 2023 · Castle Hill Intake (S00579) · 0.9%424 Apr 2023 to 25 May 2026
Acheron1 source<0.05 g/m37 May 2026 · Acheron Intake (S00580)no sharebelow the printed threshold0.06 g/m326 Apr 2023 · Acheron Intake (S00580) · 0.5%426 Apr 2023 to 7 May 2026
Arthur’s Pass1 source<0.05 g/m325 May 2026 · Arthurs Pass Intake (S00577)no sharebelow the printed threshold<0.05 g/m3every result is below the printed threshold424 Apr 2023 to 25 May 2026
Lake Coleridge1 source<0.05 g/m37 May 2026 · Lake Coleridge Intake (S00578)no sharebelow the printed threshold<0.05 g/m3every result is below the printed threshold426 Apr 2023 to 7 May 2026

Source: Selwyn Water Limited, nitrate-N readings published on its drinking water quality testing page, read 13 Oct 2026. Readings are nitrate-nitrogen in g/m3 at the source. Shares are of the legal limit of 11.3 g/m3. A result printed as <0.05 is kept as printed and has no share worked out.

EVERY SOURCE

Each bore and intake, as published

Every chart uses the same scale, from 0 up to the legal limit of 11.3 g/m3, with half the limit marked at 5.65. Source ids and sampling point names are as Selwyn Water prints them. A yearly average is the mean of that year's published results, and 2026 covers January to August only. Every individual reading is in the CSV.

Kirwee

1 source with published results and 46 results, 9 Jan 2023 to 19 Aug 2026.

Kirwee Bore

Source G00725 · 46 results

Nitrate-nitrogen at Kirwee Bore (G00725), Kirwee: 46 published readings, 9 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 5.05 to 6.26 g/m3; the highest was on 15 May 2024 and 15 Jan 2025. Latest reading 5.91 g/m3 on 19 Aug 2026, 52.3% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 5.91 g/m3 on 19 Aug 2026
First
5.19 g/m3 on 9 Jan 2023 45.9% of the limit
Latest
5.91 g/m3 on 19 Aug 2026 52.3% of the limit
Highest
6.26 g/m3 on 15 May 2024 and 15 Jan 2025 55.4% of the limit
Half limit
34 of 46 results at half the limit or more
Yearly averages, g/m3
2023202420252026January to August
5.385.855.975.89
13 results12 results12 results9 results

Back to the supply table

Rolleston

12 sources with published results and 469 results, 27 Jan 2023 to 17 Aug 2026. Highest latest reading: 5.8 g/m3 at Illinois Bore, which the published table notes as a backup source, on 18 Jun 2026, 51.3% of the limit. Among the other sources the highest latest reading is 4.78 g/m3 at Overbury Bore on 17 Aug 2026, 42.3% of the limit.

Illinois Bore

Source G02009 · 45 results

Printed note: Backup source only. Mixed with other sources if used.

Nitrate-nitrogen at Illinois Bore (G02009), Rolleston: 45 published readings, 27 Jan 2023 to 18 Jun 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 4.7 to 7.6 g/m3; the highest was on 16 May 2025. Latest reading 5.8 g/m3 on 18 Jun 2026, 51.3% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 5.8 g/m3 on 18 Jun 2026
First
7.31 g/m3 on 27 Jan 2023 64.7% of the limit
Latest
5.8 g/m3 on 18 Jun 2026 51.3% of the limit
Highest
7.6 g/m3 on 16 May 2025 67.3% of the limit
Half limit
40 of 45 results at half the limit or more
Yearly averages, g/m3
2023202420252026January to August
6.636.556.716.47
13 results12 results13 results7 results

Overbury Bore

Source G01113 · 47 results

Nitrate-nitrogen at Overbury Bore (G01113), Rolleston: 47 published readings, 27 Jan 2023 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 4.27 to 4.99 g/m3; the highest was on 11 Apr 2024. Latest reading 4.78 g/m3 on 17 Aug 2026, 42.3% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 4.78 g/m3 on 17 Aug 2026
First
4.59 g/m3 on 27 Jan 2023 40.6% of the limit
Latest
4.78 g/m3 on 17 Aug 2026 42.3% of the limit
Highest
4.99 g/m3 on 11 Apr 2024 44.2% of the limit
Yearly averages, g/m3
2023202420252026January to August
4.624.664.744.74
13 results12 results13 results9 results

Westland Bore

Source G01874 · 47 results

Nitrate-nitrogen at Westland Bore (G01874), Rolleston: 47 published readings, 27 Jan 2023 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 2.92 to 4.15 g/m3; the highest was on 24 Mar 2025. Latest reading 3.89 g/m3 on 17 Aug 2026, 34.4% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 3.89 g/m3 on 17 Aug 2026
First
3.01 g/m3 on 27 Jan 2023 26.6% of the limit
Latest
3.89 g/m3 on 17 Aug 2026 34.4% of the limit
Highest
4.15 g/m3 on 24 Mar 2025 36.7% of the limit
Yearly averages, g/m3
2023202420252026January to August
3.153.613.463.76
13 results12 results13 results9 results

Baltimore Bore

Source G03020 · 43 results

Nitrate-nitrogen at Baltimore Bore (G03020), Rolleston: 43 published readings, 27 Jan 2023 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 2.72 to 3.68 g/m3; the highest was on 22 Aug 2024. Latest reading 3.51 g/m3 on 17 Aug 2026, 31.1% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 3.51 g/m3 on 17 Aug 2026
First
2.72 g/m3 on 27 Jan 2023 24.1% of the limit
Latest
3.51 g/m3 on 17 Aug 2026 31.1% of the limit
Highest
3.68 g/m3 on 22 Aug 2024 32.6% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.963.033.103.27
13 results12 results9 results9 results

Helpet Bore 2

Source G03084 · 47 results

Nitrate-nitrogen at Helpet Bore 2 (G03084), Rolleston: 47 published readings, 27 Jan 2023 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.67 to 3.63 g/m3; the highest was on 11 Apr 2024 and 16 May 2025. Latest reading 3.5 g/m3 on 17 Aug 2026, 31.0% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 3.5 g/m3 on 17 Aug 2026
First
3.42 g/m3 on 27 Jan 2023 30.3% of the limit
Latest
3.5 g/m3 on 17 Aug 2026 31.0% of the limit
Highest
3.63 g/m3 on 11 Apr 2024 and 16 May 2025 32.1% of the limit
Yearly averages, g/m3
2023202420252026January to August
3.043.153.403.39
13 results12 results13 results9 results

Moore Bore 2

Source G02191 · 45 results

Nitrate-nitrogen at Moore Bore 2 (G02191), Rolleston: 45 published readings, 27 Jan 2023 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.72 to 3.55 g/m3; the highest was on 14 Sep 2023. Latest reading 3.47 g/m3 on 17 Aug 2026, 30.7% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 3.47 g/m3 on 17 Aug 2026
First
1.81 g/m3 on 27 Jan 2023 16.0% of the limit
Latest
3.47 g/m3 on 17 Aug 2026 30.7% of the limit
Highest
3.55 g/m3 on 14 Sep 2023 31.4% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.742.622.382.56
13 results12 results13 results7 results

Izone Bore

Source G01672 · 47 results

Nitrate-nitrogen at Izone Bore (G01672), Rolleston: 47 published readings, 27 Jan 2023 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 2.65 to 3.71 g/m3; the highest was on 27 Jan 2023. Latest reading 3.03 g/m3 on 17 Aug 2026, 26.8% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 3.03 g/m3 on 17 Aug 2026
First
3.71 g/m3 on 27 Jan 2023 32.8% of the limit
Latest
3.03 g/m3 on 17 Aug 2026 26.8% of the limit
Highest
3.71 g/m3 on 27 Jan 2023 32.8% of the limit
Yearly averages, g/m3
2023202420252026January to August
3.373.032.912.92
13 results12 results13 results9 results

Helpet Bore 1 / Helpet Bore 2

Source G02192 · 47 results

Nitrate-nitrogen at Helpet Bore 1 / Helpet Bore 2 (G02192), Rolleston: 47 published readings, 27 Jan 2023 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.72 to 3.99 g/m3; the highest was on 24 Mar 2025. Latest reading 3.03 g/m3 on 17 Aug 2026, 26.8% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 3.03 g/m3 on 17 Aug 2026
First
1.86 g/m3 on 27 Jan 2023 16.5% of the limit
Latest
3.03 g/m3 on 17 Aug 2026 26.8% of the limit
Highest
3.99 g/m3 on 24 Mar 2025 35.3% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.382.263.092.59
13 results12 results13 results9 results

Baltimore Bore 2

Source G11328 · 4 results

Nitrate-nitrogen at Baltimore Bore 2 (G11328), Rolleston: 4 published readings, 4 Jun 2026 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 2.94 to 3.5 g/m3; the highest was on 19 Jul 2026. Latest reading 2.94 g/m3 on 17 Aug 2026, 26.0% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 2.94 g/m3 on 17 Aug 2026
First
3.33 g/m3 on 4 Jun 2026 29.5% of the limit
Latest
2.94 g/m3 on 17 Aug 2026 26.0% of the limit
Highest
3.5 g/m3 on 19 Jul 2026 31.0% of the limit
Yearly averages, g/m3
2026January to August
3.20
4 results

Moore Bore 1

Source G00167 · 47 results

Nitrate-nitrogen at Moore Bore 1 (G00167), Rolleston: 47 published readings, 27 Jan 2023 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.37 to 1.77 g/m3; the highest was on 16 May 2025. Latest reading 1.63 g/m3 on 17 Aug 2026, 14.4% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.63 g/m3 on 17 Aug 2026
First
1.59 g/m3 on 27 Jan 2023 14.1% of the limit
Latest
1.63 g/m3 on 17 Aug 2026 14.4% of the limit
Highest
1.77 g/m3 on 16 May 2025 15.7% of the limit
Yearly averages, g/m3
2023202420252026January to August
1.551.601.641.60
13 results12 results13 results9 results

Rolleston (WTP) Helpet Park 2, Bore 3

Source G11196 · 25 results

Nitrate-nitrogen at Rolleston (WTP) Helpet Park 2, Bore 3 (G11196), Rolleston: 25 published readings, 15 Mar 2024 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.52 to 1.86 g/m3; the highest was on 16 Sep 2025. Latest reading 1.63 g/m3 on 17 Aug 2026, 14.4% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.63 g/m3 on 17 Aug 2026
First
1.69 g/m3 on 15 Mar 2024 15.0% of the limit
Latest
1.63 g/m3 on 17 Aug 2026 14.4% of the limit
Highest
1.86 g/m3 on 16 Sep 2025 16.5% of the limit
Yearly averages, g/m3
202420252026January to August
1.671.711.68
3 results13 results9 results

Rolleston (WTP) Helpet Park 2, Bore 4

Source G11197 · 25 results

Nitrate-nitrogen at Rolleston (WTP) Helpet Park 2, Bore 4 (G11197), Rolleston: 25 published readings, 15 Mar 2024 to 17 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.18 to 1.4 g/m3; the highest was on 16 May 2025. Latest reading 1.35 g/m3 on 17 Aug 2026, 11.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.35 g/m3 on 17 Aug 2026
First
1.32 g/m3 on 15 Mar 2024 11.7% of the limit
Latest
1.35 g/m3 on 17 Aug 2026 11.9% of the limit
Highest
1.4 g/m3 on 16 May 2025 12.4% of the limit
Yearly averages, g/m3
202420252026January to August
1.321.291.34
3 results13 results9 results

Back to the supply table

Darfield

2 sources with published results and 91 results, 10 Jan 2023 to 19 Aug 2026. Highest latest reading: 5.78 g/m3 at SH73 Bore 1 on 19 Aug 2026, 51.2% of the limit.

SH73 Bore 1

Source G01961-2 · 47 results

Nitrate-nitrogen at SH73 Bore 1 (G01961-2), Darfield: 47 published readings, 10 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 5.23 to 6.3 g/m3; the highest was on 10 Apr 2024. Latest reading 5.78 g/m3 on 19 Aug 2026, 51.2% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 5.78 g/m3 on 19 Aug 2026
First
5.26 g/m3 on 10 Jan 2023 46.5% of the limit
Latest
5.78 g/m3 on 19 Aug 2026 51.2% of the limit
Highest
6.3 g/m3 on 10 Apr 2024 55.8% of the limit
Half limit
24 of 47 results at half the limit or more
Yearly averages, g/m3
2023202420252026January to August
5.585.855.655.64
13 results12 results13 results9 results

SH73 Bore 2

Source G01961 · 44 results

Nitrate-nitrogen at SH73 Bore 2 (G01961), Darfield: 44 published readings, 12 Apr 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 4.42 to 5.47 g/m3; the highest was on 13 May 2025. Latest reading 5 g/m3 on 19 Aug 2026, 44.2% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 5 g/m3 on 19 Aug 2026
First
4.86 g/m3 on 12 Apr 2023 43.0% of the limit
Latest
5 g/m3 on 19 Aug 2026 44.2% of the limit
Highest
5.47 g/m3 on 13 May 2025 48.4% of the limit
Yearly averages, g/m3
2023202420252026January to August
4.984.974.904.85
10 results12 results13 results9 results

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Te Pirita

1 source with published results and 41 results, 26 Apr 2023 to 11 Aug 2026.

Te Pirita Bore

Source G01169 · 41 results

Nitrate-nitrogen at Te Pirita Bore (G01169), Te Pirita: 41 published readings, 26 Apr 2023 to 11 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 4.51 to 5.66 g/m3; the highest was on 17 May 2024. Latest reading 4.51 g/m3 on 11 Aug 2026, 39.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 4.51 g/m3 on 11 Aug 2026
First
5.13 g/m3 on 26 Apr 2023 45.4% of the limit
Latest
4.51 g/m3 on 11 Aug 2026 39.9% of the limit
Highest
5.66 g/m3 on 17 May 2024 50.1% of the limit
Half limit
1 of 41 results at half the limit or more
Yearly averages, g/m3
2023202420252026January to August
5.025.325.134.77
8 results13 results12 results8 results

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Dunsandel

1 source with published results and 46 results, 9 Jan 2023 to 19 Aug 2026.

Dunsandel Bore

Source G00726 · 46 results

Nitrate-nitrogen at Dunsandel Bore (G00726), Dunsandel: 46 published readings, 9 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 2.69 to 6.6 g/m3; the highest was on 15 Sep 2023. Latest reading 3.32 g/m3 on 19 Aug 2026, 29.4% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 3.32 g/m3 on 19 Aug 2026
First
4.56 g/m3 on 9 Jan 2023 40.4% of the limit
Latest
3.32 g/m3 on 19 Aug 2026 29.4% of the limit
Highest
6.6 g/m3 on 15 Sep 2023 58.4% of the limit
Half limit
1 of 46 results at half the limit or more
Yearly averages, g/m3
2023202420252026January to August
3.883.683.643.31
13 results12 results12 results9 results

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Southbridge

1 source with published results and 47 results, 27 Jan 2023 to 18 Aug 2026.

St John Bore

Source G03053 · 47 results

Nitrate-nitrogen at St John Bore (G03053), Southbridge: 47 published readings, 27 Jan 2023 to 18 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 2.84 to 3.67 g/m3; the highest was on 18 Mar 2026. Latest reading 3.32 g/m3 on 18 Aug 2026, 29.4% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 3.32 g/m3 on 18 Aug 2026
First
3.17 g/m3 on 27 Jan 2023 28.1% of the limit
Latest
3.32 g/m3 on 18 Aug 2026 29.4% of the limit
Highest
3.67 g/m3 on 18 Mar 2026 32.5% of the limit
Yearly averages, g/m3
2023202420252026January to August
3.053.053.113.25
13 results12 results13 results9 results

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Sheffield

2 sources with published results and 67 results, 9 Jan 2023 to 19 Aug 2026. Highest latest reading: 2.78 g/m3 at Sheffield Bore on 19 Aug 2026, 24.6% of the limit.

Sheffield Bore

Source G00820 · 46 results

Nitrate-nitrogen at Sheffield Bore (G00820), Sheffield: 46 published readings, 9 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.46 to 3.97 g/m3; the highest was on 16 Jun 2025. Latest reading 2.78 g/m3 on 19 Aug 2026, 24.6% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 2.78 g/m3 on 19 Aug 2026
First
1.98 g/m3 on 9 Jan 2023 17.5% of the limit
Latest
2.78 g/m3 on 19 Aug 2026 24.6% of the limit
Highest
3.97 g/m3 on 16 Jun 2025 35.1% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.152.892.782.21
13 results12 results12 results9 results

Sheffield Bore 2

Source G11246 · 21 results

Nitrate-nitrogen at Sheffield Bore 2 (G11246), Sheffield: 21 published readings, 31 Jan 2025 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.54 to 3.39 g/m3; the highest was on 16 Jun 2025. Latest reading 2.73 g/m3 on 19 Aug 2026, 24.2% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 2.73 g/m3 on 19 Aug 2026
First
2.06 g/m3 on 31 Jan 2025 18.2% of the limit
Latest
2.73 g/m3 on 19 Aug 2026 24.2% of the limit
Highest
3.39 g/m3 on 16 Jun 2025 30.0% of the limit
Yearly averages, g/m3
20252026January to August
2.562.18
12 results9 results

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Jowers Road

1 source with published results and 4 results, 26 Apr 2023 to 14 May 2026.

Jowers Bore

Source G00671 · 4 results

Nitrate-nitrogen at Jowers Bore (G00671), Jowers Road: 4 published readings, 26 Apr 2023 to 14 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 2.47 to 2.83 g/m3; the highest was on 11 Apr 2024. Latest reading 2.47 g/m3 on 14 May 2026, 21.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 2.47 g/m3 on 14 May 2026
First
2.82 g/m3 on 26 Apr 2023 25.0% of the limit
Latest
2.47 g/m3 on 14 May 2026 21.9% of the limit
Highest
2.83 g/m3 on 11 Apr 2024 25.0% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.822.832.552.47
1 result1 result1 result1 result

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Greater West Melton

5 sources with published results and 230 results, 9 Jan 2023 to 19 Aug 2026. Highest latest reading: 2.39 g/m3 at Edendale Bore on 19 Aug 2026, 21.2% of the limit.

Edendale Bore

Source G02166 · 47 results

Nitrate-nitrogen at Edendale Bore (G02166), Greater West Melton: 47 published readings, 9 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 2.12 to 2.79 g/m3; the highest was on 18 Feb 2026. Latest reading 2.39 g/m3 on 19 Aug 2026, 21.2% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 2.39 g/m3 on 19 Aug 2026
First
2.21 g/m3 on 9 Jan 2023 19.6% of the limit
Latest
2.39 g/m3 on 19 Aug 2026 21.2% of the limit
Highest
2.79 g/m3 on 18 Feb 2026 24.7% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.412.442.372.41
13 results12 results13 results9 results

Ridgeland Bore / West Melton (WTP) Dorper Rd, Bore 1 - G03061

Source G03061 · 46 results

Nitrate-nitrogen at Ridgeland Bore / West Melton (WTP) Dorper Rd, Bore 1 - G03061 (G03061), Greater West Melton: 46 published readings, 9 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.76 to 2.71 g/m3; the highest was on 10 Nov 2023. Latest reading 2.09 g/m3 on 19 Aug 2026, 18.5% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 2.09 g/m3 on 19 Aug 2026
First
1.76 g/m3 on 9 Jan 2023 15.6% of the limit
Latest
2.09 g/m3 on 19 Aug 2026 18.5% of the limit
Highest
2.71 g/m3 on 10 Nov 2023 24.0% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.212.052.212.10
13 results12 results12 results9 results

Royston Bore

Source G01775 · 43 results

Nitrate-nitrogen at Royston Bore (G01775), Greater West Melton: 43 published readings, 9 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.65 to 3.8 g/m3; the highest was on 13 Sep 2023. Latest reading 1.77 g/m3 on 19 Aug 2026, 15.7% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.77 g/m3 on 19 Aug 2026
First
3.37 g/m3 on 9 Jan 2023 29.8% of the limit
Latest
1.77 g/m3 on 19 Aug 2026 15.7% of the limit
Highest
3.8 g/m3 on 13 Sep 2023 33.6% of the limit
Yearly averages, g/m3
2023202420252026January to August
3.412.302.502.01
11 results12 results13 results7 results

Elizabeth Allen Bore

Source G01957 · 47 results

Nitrate-nitrogen at Elizabeth Allen Bore (G01957), Greater West Melton: 47 published readings, 9 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.35 to 4.19 g/m3; the highest was on 13 Sep 2023. Latest reading 1.66 g/m3 on 19 Aug 2026, 14.7% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.66 g/m3 on 19 Aug 2026
First
3.45 g/m3 on 9 Jan 2023 30.5% of the limit
Latest
1.66 g/m3 on 19 Aug 2026 14.7% of the limit
Highest
4.19 g/m3 on 13 Sep 2023 37.1% of the limit
Yearly averages, g/m3
2023202420252026January to August
3.282.082.501.85
13 results12 results13 results9 results

Jacqueline Bore

Source G01958 · 47 results

Nitrate-nitrogen at Jacqueline Bore (G01958), Greater West Melton: 47 published readings, 9 Jan 2023 to 19 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.16 to 3.58 g/m3; the highest was on 13 Oct 2023. Latest reading 1.49 g/m3 on 19 Aug 2026, 13.2% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.49 g/m3 on 19 Aug 2026
First
2.98 g/m3 on 9 Jan 2023 26.4% of the limit
Latest
1.49 g/m3 on 19 Aug 2026 13.2% of the limit
Highest
3.58 g/m3 on 13 Oct 2023 31.7% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.821.872.071.69
13 results12 results13 results9 results

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Springston

1 source with published results and 47 results, 27 Jan 2023 to 18 Aug 2026.

Springston Bore

Source G01794 · 47 results

Nitrate-nitrogen at Springston Bore (G01794), Springston: 47 published readings, 27 Jan 2023 to 18 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.82 to 2.09 g/m3; the highest was on 17 Jul 2026. Latest reading 2.06 g/m3 on 18 Aug 2026, 18.2% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 2.06 g/m3 on 18 Aug 2026
First
1.98 g/m3 on 27 Jan 2023 17.5% of the limit
Latest
2.06 g/m3 on 18 Aug 2026 18.2% of the limit
Highest
2.09 g/m3 on 17 Jul 2026 18.5% of the limit
Yearly averages, g/m3
2023202420252026January to August
1.941.971.982.02
13 results12 results13 results9 results

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Lincoln

4 sources with published results and 167 results, 27 Jan 2023 to 21 Aug 2026. Highest latest reading: 1.91 g/m3 at Kakahi Bore on 21 Aug 2026, 16.9% of the limit.

Kakahi Bore

Source G03127 · 47 results

Nitrate-nitrogen at Kakahi Bore (G03127), Lincoln: 47 published readings, 27 Jan 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.74 to 2 g/m3; the highest was on 16 Dec 2025. Latest reading 1.91 g/m3 on 21 Aug 2026, 16.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.91 g/m3 on 21 Aug 2026
First
1.98 g/m3 on 27 Jan 2023 17.5% of the limit
Latest
1.91 g/m3 on 21 Aug 2026 16.9% of the limit
Highest
2 g/m3 on 16 Dec 2025 17.7% of the limit
Yearly averages, g/m3
2023202420252026January to August
1.891.921.931.91
13 results12 results13 results9 results

Marion Pl Bore

Source G11199 · 26 results

Nitrate-nitrogen at Marion Pl Bore (G11199), Lincoln: 26 published readings, 28 Aug 2024 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.8 to 2.02 g/m3; the highest was on 28 Aug 2024. Latest reading 1.87 g/m3 on 21 Aug 2026, 16.5% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.87 g/m3 on 21 Aug 2026
First
2.02 g/m3 on 28 Aug 2024 17.9% of the limit
Latest
1.87 g/m3 on 21 Aug 2026 16.5% of the limit
Highest
2.02 g/m3 on 28 Aug 2024 17.9% of the limit
Yearly averages, g/m3
202420252026January to August
1.911.911.90
4 results13 results9 results

Eastfield Bore

Source G02129 · 47 results

Nitrate-nitrogen at Eastfield Bore (G02129), Lincoln: 47 published readings, 27 Jan 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.19 to 1.42 g/m3; the highest was on 16 Apr 2025. Latest reading 1.35 g/m3 on 21 Aug 2026, 11.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.35 g/m3 on 21 Aug 2026
First
1.34 g/m3 on 27 Jan 2023 11.9% of the limit
Latest
1.35 g/m3 on 21 Aug 2026 11.9% of the limit
Highest
1.42 g/m3 on 16 Apr 2025 12.6% of the limit
Yearly averages, g/m3
2023202420252026January to August
1.281.321.371.37
13 results12 results13 results9 results

Veuve Bore

Source G03115 · 47 results

Nitrate-nitrogen at Veuve Bore (G03115), Lincoln: 47 published readings, 27 Jan 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.14 to 1.38 g/m3; the highest was on 15 Aug 2025. Latest reading 1.28 g/m3 on 21 Aug 2026, 11.3% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.28 g/m3 on 21 Aug 2026
First
1.3 g/m3 on 27 Jan 2023 11.5% of the limit
Latest
1.28 g/m3 on 21 Aug 2026 11.3% of the limit
Highest
1.38 g/m3 on 15 Aug 2025 12.2% of the limit
Yearly averages, g/m3
2023202420252026January to August
1.261.271.311.30
13 results12 results13 results9 results

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Springfield

1 source with published results and 48 results, 9 Jan 2023 to 18 Aug 2026.

Springfield Intake

Source S10058 · 48 results

Nitrate-nitrogen at Springfield Intake (S10058), Springfield: 48 published readings, 9 Jan 2023 to 18 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.74 to 4.56 g/m3; the highest was on 9 Aug 2023. Latest reading 1.53 g/m3 on 18 Aug 2026, 13.5% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.53 g/m3 on 18 Aug 2026
First
2.32 g/m3 on 9 Jan 2023 20.5% of the limit
Latest
1.53 g/m3 on 18 Aug 2026 13.5% of the limit
Highest
4.56 g/m3 on 9 Aug 2023 40.4% of the limit
Yearly averages, g/m3
2023202420252026January to August
2.331.451.871.13
13 results12 results14 results9 results

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Leeston

2 sources with published results and 94 results, 27 Jan 2023 to 18 Aug 2026. Highest latest reading: 1.48 g/m3 at Leeston Dunsandel Bore on 18 Aug 2026, 13.1% of the limit.

Leeston Dunsandel Bore

Source G03119 · 47 results

Nitrate-nitrogen at Leeston Dunsandel Bore (G03119), Leeston: 47 published readings, 27 Jan 2023 to 18 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.24 to 1.72 g/m3; the highest was on 8 Apr 2024. Latest reading 1.48 g/m3 on 18 Aug 2026, 13.1% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.48 g/m3 on 18 Aug 2026
First
1.65 g/m3 on 27 Jan 2023 14.6% of the limit
Latest
1.48 g/m3 on 18 Aug 2026 13.1% of the limit
Highest
1.72 g/m3 on 8 Apr 2024 15.2% of the limit
Yearly averages, g/m3
2023202420252026January to August
1.541.611.571.57
13 results12 results13 results9 results

Gallipoli Bore

Source G00501 · 47 results

Nitrate-nitrogen at Gallipoli Bore (G00501), Leeston: 47 published readings, 27 Jan 2023 to 18 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.89 to 1.13 g/m3; the highest was on three dates, most recently 18 Aug 2026. Latest reading 1.13 g/m3 on 18 Aug 2026, 10.0% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.13 g/m3 on 18 Aug 2026
First
1.01 g/m3 on 27 Jan 2023 8.9% of the limit
Latest
1.13 g/m3 on 18 Aug 2026 10.0% of the limit
Highest
1.13 g/m3 on three dates, most recently 18 Aug 2026 10.0% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.981.031.061.08
13 results12 results13 results9 results

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Taumutu

1 source with published results and 4 results, 26 Apr 2023 to 14 May 2026.

Taumutu Bore

Source G00680 · 4 results

Nitrate-nitrogen at Taumutu Bore (G00680), Taumutu: 4 published readings, 26 Apr 2023 to 14 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.37 to 1.48 g/m3; the highest was on 11 Mar 2025. Latest reading 1.47 g/m3 on 14 May 2026, 13.0% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.47 g/m3 on 14 May 2026
First
1.37 g/m3 on 26 Apr 2023 12.1% of the limit
Latest
1.47 g/m3 on 14 May 2026 13.0% of the limit
Highest
1.48 g/m3 on 11 Mar 2025 13.1% of the limit
Yearly averages, g/m3
2023202420252026January to August
1.371.411.481.47
1 result1 result1 result1 result

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Claremont

1 source with published results and 4 results, 26 Apr 2023 to 25 May 2026.

Claremont Bore

Source G01673 · 4 results

Nitrate-nitrogen at Claremont Bore (G01673), Claremont: 4 published readings, 26 Apr 2023 to 25 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 1.18 to 1.3 g/m3; the highest was on 25 May 2026. Latest reading 1.3 g/m3 on 25 May 2026, 11.5% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 1.3 g/m3 on 25 May 2026
First
1.18 g/m3 on 26 Apr 2023 10.4% of the limit
Latest
1.3 g/m3 on 25 May 2026 11.5% of the limit
Highest
1.3 g/m3 on 25 May 2026 11.5% of the limit
Yearly averages, g/m3
2023202420252026January to August
1.181.201.271.30
1 result1 result1 result1 result

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Prebbleton

4 sources with published results and 168 results, 27 Jan 2023 to 21 Aug 2026. Highest latest reading: 0.78 g/m3 at Tosswill Bore 2 on 21 Aug 2026, 6.9% of the limit.

Tosswill Bore 2

Source G00463 · 37 results

Nitrate-nitrogen at Tosswill Bore 2 (G00463), Prebbleton: 37 published readings, 25 Oct 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.74 to 0.83 g/m3; the highest was on 16 Apr 2025 and 16 Dec 2025. Latest reading 0.78 g/m3 on 21 Aug 2026, 6.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.78 g/m3 on 21 Aug 2026
First
0.75 g/m3 on 25 Oct 2023 6.6% of the limit
Latest
0.78 g/m3 on 21 Aug 2026 6.9% of the limit
Highest
0.83 g/m3 on 16 Apr 2025 and 16 Dec 2025 7.3% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.760.790.800.80
3 results12 results13 results9 results

Tosswill Bore 3

Source G02128 · 37 results

Nitrate-nitrogen at Tosswill Bore 3 (G02128), Prebbleton: 37 published readings, 25 Oct 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.68 to 0.79 g/m3; the highest was on 16 Apr 2025 and 15 Aug 2025. Latest reading 0.74 g/m3 on 21 Aug 2026, 6.5% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.74 g/m3 on 21 Aug 2026
First
0.7 g/m3 on 25 Oct 2023 6.2% of the limit
Latest
0.74 g/m3 on 21 Aug 2026 6.5% of the limit
Highest
0.79 g/m3 on 16 Apr 2025 and 15 Aug 2025 7.0% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.720.730.760.75
3 results12 results13 results9 results

Tosswill Bore 1

Source G00165 · 47 results

Nitrate-nitrogen at Tosswill Bore 1 (G00165), Prebbleton: 47 published readings, 27 Jan 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.66 to 0.81 g/m3; the highest was on 10 May 2023. Latest reading 0.71 g/m3 on 21 Aug 2026, 6.3% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.71 g/m3 on 21 Aug 2026
First
0.79 g/m3 on 27 Jan 2023 7.0% of the limit
Latest
0.71 g/m3 on 21 Aug 2026 6.3% of the limit
Highest
0.81 g/m3 on 10 May 2023 7.2% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.740.730.750.72
13 results12 results13 results9 results

Shands Bore

Source G03114 · 47 results

Nitrate-nitrogen at Shands Bore (G03114), Prebbleton: 47 published readings, 27 Jan 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.44 to 0.57 g/m3; the highest was on five dates, most recently 14 Oct 2025. Latest reading 0.54 g/m3 on 21 Aug 2026, 4.8% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.54 g/m3 on 21 Aug 2026
First
0.54 g/m3 on 27 Jan 2023 4.8% of the limit
Latest
0.54 g/m3 on 21 Aug 2026 4.8% of the limit
Highest
0.57 g/m3 on five dates, most recently 14 Oct 2025 5.0% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.520.530.550.55
13 results12 results13 results9 results

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Rakaia Huts

1 source with published results and 4 results, 26 Apr 2023 to 25 May 2026.

Rakaia Huts Bore

Source G00668 · 4 results

Nitrate-nitrogen at Rakaia Huts Bore (G00668), Rakaia Huts: 4 published readings, 26 Apr 2023 to 25 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.69 to 0.77 g/m3; the highest was on 28 Mar 2025. Latest reading 0.76 g/m3 on 25 May 2026, 6.7% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.76 g/m3 on 25 May 2026
First
0.69 g/m3 on 26 Apr 2023 6.1% of the limit
Latest
0.76 g/m3 on 25 May 2026 6.7% of the limit
Highest
0.77 g/m3 on 28 Mar 2025 6.8% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.690.690.770.76
1 result1 result1 result1 result

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Hartleys Road

1 source with published results and 47 results, 9 Jan 2023 to 21 Aug 2026.

Hartley's Intake

Source S00828 · 47 results

Nitrate-nitrogen at Hartley's Intake (S00828), Hartleys Road: 47 published readings, 9 Jan 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.3 to 1.21 g/m3; the highest was on 14 Jul 2026. Latest reading 0.51 g/m3 on 21 Aug 2026, 4.5% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.51 g/m3 on 21 Aug 2026
First
0.58 g/m3 on 9 Jan 2023 5.1% of the limit
Latest
0.51 g/m3 on 21 Aug 2026 4.5% of the limit
Highest
1.21 g/m3 on 14 Jul 2026 10.7% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.580.570.530.46
13 results12 results13 results9 results

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Dalethorpe

1 source with published results and 4 results, 24 Apr 2023 to 26 May 2026.

Dalethorpe Intake

Source S00827 · 4 results

Nitrate-nitrogen at Dalethorpe Intake (S00827), Dalethorpe: 4 published readings, 24 Apr 2023 to 26 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.21 to 0.83 g/m3; the highest was on 24 Apr 2023. Latest reading 0.44 g/m3 on 26 May 2026, 3.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.44 g/m3 on 26 May 2026
First
0.83 g/m3 on 24 Apr 2023 7.3% of the limit
Latest
0.44 g/m3 on 26 May 2026 3.9% of the limit
Highest
0.83 g/m3 on 24 Apr 2023 7.3% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.830.210.500.44
1 result1 result1 result1 result

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Hororātā

1 source with published results and 47 results, 9 Jan 2023 to 21 Aug 2026.

Hororata Intake

Source G00822 · 47 results

Nitrate-nitrogen at Hororata Intake (G00822), Hororātā: 47 published readings, 9 Jan 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.18 to 0.8 g/m3; the highest was on 15 Aug 2024. Latest reading 0.33 g/m3 on 21 Aug 2026, 2.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.33 g/m3 on 21 Aug 2026
First
0.33 g/m3 on 9 Jan 2023 2.9% of the limit
Latest
0.33 g/m3 on 21 Aug 2026 2.9% of the limit
Highest
0.8 g/m3 on 15 Aug 2024 7.1% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.400.370.360.29
13 results12 results13 results9 results

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Tai Tapu

1 source with published results and 47 results, 27 Jan 2023 to 21 Aug 2026.

Tai Tapu Bore

Source G00675 · 47 results

Nitrate-nitrogen at Tai Tapu Bore (G00675), Tai Tapu: 47 published readings, 27 Jan 2023 to 21 Aug 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.29 to 0.37 g/m3; the highest was on 15 Aug 2025. Latest reading 0.33 g/m3 on 21 Aug 2026, 2.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.33 g/m3 on 21 Aug 2026
First
0.33 g/m3 on 27 Jan 2023 2.9% of the limit
Latest
0.33 g/m3 on 21 Aug 2026 2.9% of the limit
Highest
0.37 g/m3 on 15 Aug 2025 3.3% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.320.320.340.34
13 results12 results13 results9 results

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Upper Selwyn Huts

1 source with published results and 4 results, 26 Apr 2023 to 14 May 2026.

Upper Selwyn Huts Bore

Source G01315 · 4 results

Nitrate-nitrogen at Upper Selwyn Huts Bore (G01315), Upper Selwyn Huts: 4 published readings, 26 Apr 2023 to 14 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.22 to 0.26 g/m3; the highest was on 11 Apr 2024. Latest reading 0.22 g/m3 on 14 May 2026, 1.9% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.22 g/m3 on 14 May 2026
First
0.23 g/m3 on 26 Apr 2023 2.0% of the limit
Latest
0.22 g/m3 on 14 May 2026 1.9% of the limit
Highest
0.26 g/m3 on 11 Apr 2024 2.3% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.230.260.240.22
1 result1 result1 result1 result

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Castle Hill

1 source with published results and 4 results, 24 Apr 2023 to 25 May 2026.

Castle Hill Intake

Source S00579 · 4 results

Nitrate-nitrogen at Castle Hill Intake (S00579), Castle Hill: 4 published readings, 24 Apr 2023 to 25 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.06 to 0.1 g/m3; the highest was on 24 Apr 2023. Two of the readings are printed as <0.05 and drawn as open circles on the zero line. Latest reading 0.06 g/m3 on 25 May 2026, 0.5% of the limit.11.35.650Legal limitHalf the limit2023202420252026Latest: 0.06 g/m3 on 25 May 2026
First
0.1 g/m3 on 24 Apr 2023 0.9% of the limit
Latest
0.06 g/m3 on 25 May 2026 0.5% of the limit
Highest
0.1 g/m3 on 24 Apr 2023 0.9% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.10nonenone0.06
1 result1 result1 result1 result

No average is given for a year that holds a result printed as <0.05.

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Acheron

1 source with published results and 4 results, 26 Apr 2023 to 7 May 2026.

Acheron Intake

Source S00580 · 4 results

Nitrate-nitrogen at Acheron Intake (S00580), Acheron: 4 published readings, 26 Apr 2023 to 7 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). Readings run from 0.06 to 0.06 g/m3; the highest was on 26 Apr 2023. Three of the readings are printed as <0.05 and drawn as open circles on the zero line. Latest reading <0.05 g/m3 on 7 May 2026.11.35.650Legal limitHalf the limit2023202420252026Latest: <0.05 g/m3 on 7 May 2026
First
0.06 g/m3 on 26 Apr 2023 0.5% of the limit
Latest
<0.05 g/m3 on 7 May 2026
Highest
0.06 g/m3 on 26 Apr 2023 0.5% of the limit
Yearly averages, g/m3
2023202420252026January to August
0.06nonenonenone
1 result1 result1 result1 result

No average is given for a year that holds a result printed as <0.05.

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Arthur’s Pass

1 source with published results and 4 results, 24 Apr 2023 to 25 May 2026.

Arthurs Pass Intake

Source S00577 · 4 results

Nitrate-nitrogen at Arthurs Pass Intake (S00577), Arthur’s Pass: 4 published readings, 24 Apr 2023 to 25 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). All 4 readings are printed as <0.05 and are drawn as open circles on the zero line. Latest reading <0.05 g/m3 on 25 May 2026.11.35.650Legal limitHalf the limit2023202420252026Latest: <0.05 g/m3 on 25 May 2026
First
<0.05 g/m3 on 24 Apr 2023
Latest
<0.05 g/m3 on 25 May 2026
Highest
<0.05 g/m3 every result is below the printed threshold
Yearly averages, g/m3
2023202420252026January to August
nonenonenonenone
1 result1 result1 result1 result

No average is given for a year that holds a result printed as <0.05.

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Lake Coleridge

1 source with published results and 4 results, 26 Apr 2023 to 7 May 2026.

Lake Coleridge Intake

Source S00578 · 4 results

Nitrate-nitrogen at Lake Coleridge Intake (S00578), Lake Coleridge: 4 published readings, 26 Apr 2023 to 7 May 2026Scale 0 to 11.3 g/m3, with lines at the legal limit (11.3) and at half of it (5.65). All 4 readings are printed as <0.05 and are drawn as open circles on the zero line. Latest reading <0.05 g/m3 on 7 May 2026.11.35.650Legal limitHalf the limit2023202420252026Latest: <0.05 g/m3 on 7 May 2026
First
<0.05 g/m3 on 26 Apr 2023
Latest
<0.05 g/m3 on 7 May 2026
Highest
<0.05 g/m3 every result is below the printed threshold
Yearly averages, g/m3
2023202420252026January to August
nonenonenonenone
1 result1 result1 result1 result

No average is given for a year that holds a result printed as <0.05.

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THE 2026 ANNUAL SOURCE ROUND

The wider chemistry at all 50 sources

Selwyn Water says all its sources are tested annually for a full chemical profile. Its Annual Chemical Analysis Report - 2026 lists 37 measures for the same 50 sources. It prints no sample dates.

Nothing above a printed limit

No result in the report is above a limit printed in it. The only results above half a printed limit are nitrate, at three sources: 6.3 at Rolleston's Illinois Bore (G02009), 6 at Darfield's SH73 Bore 1 (G01961-2) and 5.8 at the Kirwee Bore (G00725), all as nitrate-nitrogen against 11.3. The report prints these to fewer figures than the readings table, where the 2026 annual samples at the same sources read 6.31, 5.96 and 5.83.

Metals

Nine measures were below detection at all 50 sources: total antimony, arsenic, barium, boron, cadmium, chromium, mercury, nickel and selenium. Lead was reported at 44 sources and was below detection at six. The highest lead result is 0.00118 g/m³ at Rolleston's Baltimore Bore 2 (G11328), which is 11.8% of the 0.01 limit printed in the report.

Hardness, fluoride and pH

Total hardness runs from 22 g/m³ as CaCO₃ at the Castle Hill Intake (S00579) to 70 at Rolleston's Illinois Bore (G02009), against a printed guideline value of under 200. Fluoride runs from below 0.05 to 0.15 g/m³ against a printed limit of 1.5. One result is outside a printed guideline value: pH 6.7 at Hartley's Intake (S00828), where the printed guideline range is 7.0 to 8.5.

Source: Selwyn Water Limited, Annual Chemical Analysis Report - 2026 (PDF, created 6 Jul 2026), read 13 Oct 2026. Units are as printed, g/m³, which is the same as mg/L. The report prints a nitrate row and a nitrate-nitrogen row for every source; the nitrate-nitrogen row is the one used here.

WHAT HAS NOT BEEN PUBLISHED

Chlorine, bacteria, by-products and tap metals are not public.

Selwyn Water publishes nitrate at its sources and the yearly source chemistry above. Its chlorine readings, bacteria results, disinfection by-product results and metals measured at the tap are not public.

We have asked Selwyn Water for those under the Local Government Official Information and Meetings Act 1987 (LGOIMA), and its answer is due about 21 October 2026. In that correspondence Selwyn Water stated that no fluoridation occurs in the district. When the answer arrives, this page will be updated with it.

Get told when Selwyn's remaining results arrive

Leave an email address and we will send one email when Selwyn Water's remaining results arrive or the numbers on this page change. The suburb is filled in as Selwyn so the sign-up is tied to this page.

AT HOME

What households do about nitrate

Boiling does not remove nitrate, and neither do plain filters, ultraviolet units or chlorine, according to Household water supplies, the guide ESR (now PHF Science) publishes for households that run their own supply. The same guide rates activated carbon as poor for nitrate and two kinds of point-of-use device as good: ion exchange with a resin chosen for the job, and reverse osmosis.

The Pentair ES60 we sell is an under-bench reverse osmosis unit, and Pentair's brochure for it lists nitrate nitrogen among the substances the unit reduces, citing independent lab report FW250926-28-C.

That brochure gives no percentage for nitrate, and we do not yet hold an independent nitrate percentage for the ES60, so we do not quote one.

Questions about any of this? Call us on 021 709 370.

SELWYN WATER QUESTIONS

Straight answers.

11.3 mg/L measured as nitrate-nitrogen, which is the same limit as 50 mg/L measured as nitrate. It is set in the Water Services (Drinking Water Standards for New Zealand) Regulations 2022. Selwyn Water prints its results as nitrate-nitrogen in g/m3, and one g/m3 is the same as one mg/L.
No published result is at or above it. Across 1,742 results from 9 Jan 2023 to 21 Aug 2026, the highest is 7.6 g/m3 at Rolleston's Illinois Bore (G02009) on 16 May 2025, which is 67.3% of the limit. Selwyn Water's published table notes that bore as a backup source, mixed with other sources if used.
Five of the 50: Rolleston's Illinois Bore (G02009) with 40 of its 45 results, the Kirwee Bore (G00725) with 34 of 46 results, Darfield's SH73 Bore 1 (G01961-2) with 24 of 47 results and one result each at the Dunsandel Bore (G00726) on 15 Sep 2023 and the Te Pirita Bore (G01169) on 17 May 2024. Half the limit is 5.65 g/m3.
No. They are readings at the source, the bore or the intake, as Selwyn Water publishes them. Chlorine, bacteria, disinfection by-product and tap metal results are not public. They have been requested from Selwyn Water under LGOIMA and the answer is due about 21 October 2026.
Selwyn Water stated, in reply to our official information request, that no fluoridation occurs in the district. In its 2026 source chemistry report, fluoride at the sources ranges from below 0.05 to 0.15 g/m³ against a printed limit of 1.5.
No. Household water supplies, the guide ESR (now PHF Science) publishes for households that run their own supply, rates boiling as giving no removal of nitrate. It rates ion exchange with a resin chosen for the job, and reverse osmosis, as good at removing it.

SOURCES AND METHOD

Where the numbers come from

  • The nitrate readings come from Selwyn Water Limited's Drinking water quality testing page, from the readings table under its nitrate-N graph. Selwyn Water says the results are shown as nitrate-nitrogen in g/m3, are updated monthly and are analysed in an IANZ accredited laboratory.
  • The source chemistry comes from Selwyn Water's Annual Chemical Analysis Report - 2026 (PDF).
  • The figures were read on 13 October 2026. When read, the readings table had last been refreshed on 10 Sep 2026 and its most recent sample was dated 21 Aug 2026.
  • Every reading is nitrate-nitrogen at the source, the bore or the intake, as published. None is a kitchen-tap sample.
  • 11.3 mg/L as nitrate-nitrogen is the same legal limit as 50 mg/L as nitrate. It is set in the Water Services (Drinking Water Standards for New Zealand) Regulations 2022, and the regulator, Taumata Arowai, sets out the two ways of writing it. Selwyn Water prints g/m3, which is the same as mg/L.
  • A share of the limit is the printed reading divided by 11.3, to one decimal place. Results printed as <0.05 (13 of the 1,742) are kept as printed, carry no share and are drawn as open circles on a chart's zero line.
  • Half the limit is 5.65 g/m3. Results counted as at half the limit or more are the ones Selwyn Water's published table places in its band from 5.65 to 11.3.
  • A supply's latest reading is the highest of its sources' latest readings. A yearly average is the mean of that calendar year's published results at one source, and no average is given for a year that holds a result printed as <0.05. 2026 covers January to August only.
  • Source ids and sampling point names are as printed. Two sources carry more than one sampling point name in the published table: Greater West Melton G03061 (Ridgeland Bore and West Melton (WTP) Dorper Rd, Bore 1 - G03061) and Rolleston G02192 (Helpet Bore 1 and Helpet Bore 2). The CSV lists every printed name for those sources.
  • Download all 1,742 readings as a CSV. Each row gives the supply, the source id, the sampling point as printed, the date, the value as printed, the unit and the sample type.
  • No Brainer Water Co. is independent of Selwyn Water. If a figure here differs from Selwyn Water's own page, theirs is the record. Tell us on 021 709 370 or at hello@nobrainerwater.co.nz and we will correct it.