Friends of Golden Bay (Inc) Submission 0922 Expert evidence by Dr - - PowerPoint PPT Presentation

Friends of Golden Bay (Inc) Submission 0922

Expert evidence by Dr Donald J Mead Golden Bay

B.Sc. (NZ); B.Sc. (Edin); PhD (Fla.); FNZIF; IAH

The sacred Te Waikoropupū Main Spring with exceptional clarity and very high ecological values

Inside the Arthur Marble Auifer

Inside the Arthur Marble Aquifer

Photo Neil Silverwood

Updated Friends of Golden Bay results

• Lowess (LOcally Weighted Scatterplot Smoothing) explains 72 and 71% of the

variation for the Main and Fish Springs, respectively.

Nitrate-N (mg/l) Date

Nitrate-N in the Main and Fish Springs (FoGB data)

1/12/15 1/3/16 1/6/16 1/9/16 1/12/16 1/3/17 1/6/17 1/9/17 1/12/17 1/3/18 0.30 0.35 0.40 0.45 0.50

Legend Main NO3-N Fish NO3-N Lowess (Main NO3) Lowess (Fish NO3)

Updated statistical results

• Seasonal changes

– Main Spring - not significant – Fish Spring - highly significant; lowest in summer & highest in winter

• Sudden increase by 0.04 mg/l in March

2017 (10% increase)

– Statistically a highly significant change

• March 2017 increase:

– Very highly significant (P <0.0000) but means and standard deviations have hardly changed from the earlier submission.

Median (mg/l N) Mean (mg/l N) SD (mg/l) Main Spring

Before 19/3/17 0.395 0.395 0.0169 After 19/3/17 0.440 0.442 0.0133

Fish Spring

Before 19/3/17 0.360 0.362 0.0246 After 19/3/17 0.400 0.408 0.0228

Updated – also uses Stewart’s new analysis

• This analysis assumes the simple shallow/deep aquifer

model is realistic.

• Gives a feel of where the nitrate is coming from.

Pre mid-March 2017 Post mid-March 2017 Shallow aquifer Deep aquifer Shallow aquifer Deep aquifer Nitrate-N (mg/l) 0.350 0.401 0.396 0.457 Nitrate-N (t/year) Fish Springs Main Springs Total % from shallow aquifer 30.7 26.2 56.9 9.0 97.0 106.0 34.7 29.6 64.3 10.0 108.3 118.3

35% 35%

Discussion and conclusions

• Nitrate in Springs is increasing and has reached

the limit suggested by NIWA

• 35% of nitrate discharged from Springs comes

from ‘shallow aquifer’

• This is based on the assumption that the simple

Stewart and Thomas model is OK

• If setting limits the sampling strategy must also

be defined

• In the paper I have suggested how the FoGB

data may be used to decide on an efficient sampling strategy

Nitrate-N in the Eastern Valley Creeks

Median Nitrate-N (mg/l) Range Nitrate-N (mg/l) Ironstone Creek 0.03 0.03 – 0.04 Gorge Creek 0.09 0.06 – 0.11 Rameka Creek 0.44 0.41 – 0.45 Small Spring 0.23 0.10 – 0.36 Takaka River at Harwood* 0.005 <0.001 – 0.028

* Based on data from 2005 to 2015.

There is already a 50 fold increase in nitrate from land-use

The Spring’s Phosphate (DRP) results

• The median DRP is 0.005 mg/l for both Springs
• Range 0.003 to 0.008 mg/l
• Takaka river at Harwoods 2005-2015
• Median 0.0015 mg/l (range <0.001 – 0.003)
• The AMA is being contaminated by P
• DRP (mg/l)

Date

Dissolved Reactive Phosphate in the Main and Fish Springs since February 2016

1/12/15 1/3/16 1/6/16 1/9/16 1/12/16 1/3/17 1/6/17 1/9/17 1/12/17 1/3/18 0.000 0.002 0.004 0.006 0.008 0.010

Legend Main P Fish P Lowess (Main P) Lowess (Fish P)

Fish Creek results

• Samples collected at the reserve boundary
• NO3 –N and DRP wash off dairy farms – a wider

problem than just Fish Creek.

Creek NO3-N (mg/l) Creek DRP (mg/l) Date

Nitrate-N and DRP in Fish Creek since February 2016

1/12/15 1/3/16 1/6/16 1/9/16 1/12/16 1/3/17 1/6/17 1/9/17 1/12/17 1/3/18 0.0 0.1 0.2 0.3 0.4 0.5 0.00 0.05 0.10 0.15 0.20 0.25

Legend NO3-N DRP

• E. coli in Fish Creek
• Sampled on 23 occasions since Nov 2016 and

at several points in the catchment.

• Initial study confirmed DOCs earlier results that
• E. coli is not in the Main Spring itself.
• E. coli can be very high (e.g. >24000 /100 mm)
• n occasions.

– depending on dairy cattle grazing patterns

• This study is indicative of a widespread problem.

• E. coli changes during a rain event

Discussion and Conclusions

The National Policy Statement for Freshwater Management states that water quality must be maintained or improved

• Nitrate-N has increased in both Springs over the

27 months

• It is now at 0.44 mg/l

– This therefore should be the upper limit for NO3-N

• The median PRP is 0.005 mg/l.

– This is substantially higher than measured at Harwood’s on the Takaka river. – The upper limit for DRP should be 0.005 mg/l

• Nitrate, phosphate and E. coli wash off pastures

into streams and rivers

– These also need to be addressed by the Tribunal

Thank You