Water quality in the Orari River

catchment

Graeme Clarke

Topics

• Life supporting capacity?

• Other catchment values

• Ecosystem health

• Periphyton and macrophytes

• Abiotic factors (nutrients, sediment, temp, DO)

• Contact recreation

• Summary

Life supporting capacity

• Direct measures

– Fish community

– Invertebrate community

– Algae and macrophyte community

Water quantity Water quality

Habitat quality

Life supporting capacity

Life supporting capacity

Toxicants

Water clarity

Habitat

Temperature

Useable area/ flow

Periphyton/ macrophyte

coverage

Dissolved

oxygen

pH

Sedimentation/ substrate

Connectivity

Spawning

substrate

• Indirect measures

Other values…

• Recreation / aesthetic • E. coli

• Potentially toxic algae

• Mahinga kai • E. coli

• Potentially toxic algae

• Toxicants

• Availability

• Irrigation and potable supplies

Ecosystem health

• QMCI?

Ecosystem health

QM

CI

Ora

ri River

- Lo

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Oha

pi C

reek

Nor

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Pet

ries Dra

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Oha

pi C

reek

- Guild rd

Oha

pi C

reek

Sou

th B

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h

Oha

pi C

reek

-u/s O

rari

Coo

pers

Cre

ek-S

H72

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2

3

4

5

6

7

8

Ecosystem health

Site Location Source of Flow

Trend p Value

% change per annum

Orari River Lochaber Road Hill_upland 0.569 NA

Ohapi Creek North branch

Guild Road SF_plains 0.79 NA

Rhodes Stream

Parke Rd and Donahue Rd SF_plains 0.044 2.404

Petries Drain Canal Road SF_plains 0.277 NA

Rhodes Stream

Rolleston Road SF_plains 0.091 NA

Ohapi Creek Guild Rd SF_plains 0.704 NA

Ohapi Creek South Branch

Guild Rd SF_plains 0.495 NA

Ohapi Creek upstream Orari River

Confluence SF_plains 0.046 -2.414

Orakipaoa Creek

Milford Lagoon Rd SF_plains 0.171 NA

Coopers Creek

SH72 SF_plains 0.283 NA

Algae and macrophytes

• Ecosystem and aesthetic/

recreational impacts at high levels of

cover

• Growth regulated by nutrient

availability, flow, light, temperature

etc

• Ecosystem and aesthetic/

recreational and land drainage

impacts at high levels of cover

• Growth regulated by sediment

cover, nutrient availability, flow, light,

temperature etc

Algae

Chlorophyll A biomass?

Algae • Upper Orari River (Gorge)

• Didymo, but no filamentous algae or cyanobacteria

issues

• Lower Orari River

• NPS Band C for Chl A

• Seldom exceeds filamentous algae threshold

• Petries Creek

• Infrequent breaches of filamentous algae threshold

• Rhodes Creek

• No major algal issues until lower down and below old

lagoon

• Coopers Creek – SH72

• Infrequent Cyanobacteria blooms

• Ohapi Creek

• No issues in lower reaches

Macrophytes

• LWRP objectives

• No NPS objectives,

yet….

Macrophytes

• An issue in all spring fed streams we

monitor in the catchment, except in

upper Coopers Creek.

• Not an issue in the Orari River

Toxicity

Toxicity Nitrate Ammonia

2014-15 2014-15

Ohapi Creek -

Lower A A

Orari Gorge A A

Orari River - Parke

Rd B A

Rhodes Stream D A

Temperature, dissolved oxygen

and pH • Temperature

• Affects metabolism, and can cause behavioural changes

• Related to ambient temperature, source of flow, flow

volume and shading

• pH

• Influenced by catchment geology, dissolved oxygen, and

therefore flow source and eutrophication

• Dissolved Oxygen

• A requirement for aquatic life

• Influenced by temperature, water velocity/depth and

primary productivity

Temperature, dissolved oxygen

and pH • Temperature <19oC

• Lower Orari River??

• pH 6.5 – 8.5 • No obvious issues

• Dissolved Oxygen >90% • Spring fed sites, except

upper Coopers Creek

But……….

Sedimentation

• Why is it an issue?

• Where is it an issue?

Physico-chemical parameters

Long term site trends

Site

Total

suspended

solids

Ammonia

nitrogen

Nitrate and

nitrite nitrogen

Dissolved

reactive

phosphorus

E coli

P RSKSE P RSKSE P RSKSE P RSKSE P RSKSE

North Branch Ohapi Creek

Guild Rd 0.000 -8.9 0.000 -7.6 0.059 2.4 0.026 -2.9 0.908 0.0

Ohapi Creek Above Orari

Confluence 0.002 -4.9 0.000 -7.2 0.233 1.1 0.040 -3.1 0.823 1.1

Ohapi Creek Guild Rd 0.000 -5.0 0.000 -7.3 0.053 3.0 0.489 -0.8 0.105 -4.2

South Branch Ohapi

Creek Guild Rd 0.231 -1.9 0.000 -6.1 0.406 0.8 0.181 -2.5 0.436 2.3

• Reduction seen in TSS and

ammonium nitrogen in Ohapi

Creek catchment

10 year trends

Site

Total suspended

solids

Ammonia

nitrogen

Nitrate and

nitrite nitrogen

Dissolved

reactive

phosphorus

E coli

P RSKSE P RSKSE P RSKSE P RSKSE P RSKSE

Coopers Creek SH72 Bridge 0.617 -1.9 0.004 -9.9 0.215 4.9 0.479 -1.6 0.320 6.6

North Branch Ohapi Creek

Guild Rd 0.263 -2.8 0.077 -5.0 0.165 4.4 0.445 -2.4 0.324 5.2

Ohapi Creek Above Orari

Confluence 0.244 4.2 0.061 -6.2 0.574 1.3 0.052 -5.0 0.031 8.5

Ohapi Creek Guild Rd 0.323 -2.4 0.116 -6.4 0.020 7.0 0.687 -1.1 0.126 5.0

Orari River Mouth Reserve 0.302 -3.5 0.015 -5.4 0.057 2.1 0.163 -2.4 0.022 9.9

Orari River Parke Rd 0.929 0.4 0.000 -10.3 0.559 2.1 0.649 0.0 0.139 4.8

Petries Drain Canal Road 0.637 -14.6 0.033 -17.9 0.374 -0.8 0.156 -22.3 0.017 4.3

Rhodes Stream Parke Road 0.589 -1.5 0.000 -14.6 0.299 1.3 0.011 -12.4 0.502 -3.1

South Branch Ohapi Creek

Guild Rd 0.685 -0.8 0.590 1.0 0.028 -7.9 0.066 7.0

Current state –physico chemical

analysis

Median

TSS Median

NNN Median

DRP Median

E.coli Median

E.coli

mg/L mg/L mg/L MPN/100m

L MPN/100m

L

Coopers Creek SH72 Bridge 1.5 0.900 0.003 299 1812

North Branch Ohapi Creek Guild Rd 5.3 0.665 0.007 270 1987

Ohapi Creek Above Orari Confluence 6.1 0.795 0.018 622 2420

Ohapi Creek Guild Rd 7.2 0.765 0.032 534 2410

Orari River Mouth Reserve 2.0 9.350 0.008 291 2410

Orari River Parke Rd 1.5 1.365 0.003 40 719

Petries Drain Canal Road 1.4 5.350 0.003 175 2400

Rhodes Stream Parke Road 2.1 10.650 0.002 113 2402

South Branch Ohapi Creek Guild Rd 5.6 0.975 0.011 564 2420

Periphyton limits – 40 day accrual (actually 38.3)

DIN – 0.034mg/L, DRP – 0.0028mg/L

Contact recreation

NPS A

band

Contact recreation

Based on E. coli results from the

lower Orari River, it is likely this

site would be graded Poor, or

Very Poor (NPS C band)

Other sites are generally not

suitable for contact recreation

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Rhodes Creek at Rolleston Rd

Contact recreation

• Toxic cyanobacteria (toxin, taste)

• Regular blooms in lower Orari River during

the summer

From Heath

2014

Conclusions

• Spring fed systems most impacted, by

sediment, macrophytes, and nutrients

• Nitrogen elevated in lower Orari River,

and likely to be contributing to

periphyton (incl. cyanobacteria) blooms

in addition to other factors