DAIRY FARMING AND
WATER QUALITY
AS 90653
Contents

Dairy farm contaminants and waterways
Effluent
 Nutrients
 Agrichemicals
 Sediments


Dairy farm actions to mitigate
Riparian Planting
 Effluent Management
 Nutrient Management
 Managing Waterways

Effluent

Poor effluent management can result
in:
direct discharge into waterways
 indirect entry via surface runoff
 contamination of groundwater


Effluent can contain stormwater,
spilled milk, soil and feed residue,
detergents and other chemicals, in
addition to the faeces, urine and
washdown water.
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more?
Best Practice
Management of
Dairy Farms
being irrigated
Effluent

The organic matter in effluent
requires oxygen to break it down.
This is measured in terms of its
Biological Oxygen Demand (BOD).
The oxygen needed to break
down organic matter in effluent
could otherwise be used by
aquatic life. Therefore, effluent
breakdown poses a threat to plant
and animal life within a waterway.
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Best Practice
Management of
Dairy Farms
being irrigated
Effluent

New Zealand's clean, green and
unpolluted status is invaluable. It
must be protected through farm
management practices. World
markets are becoming increasingly
interested in the cleanliness of the
farm dairy and the practices that
are carried out there.
This info from Waikato Regional Council – see report
managing farm dairy effluent
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more?
Best Practice
Management of
Dairy Farms
being irrigated
Effluent

The nutrients in effluent can cause
excessive growth of bacterial and
fungal slimes. These growths can
change the quality of aquatic
ecosystems, raise the pH of the
water, and cause the death of
sensitive animals and plants.
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Best Practice
Management of
Dairy Farms
being irrigated
Effluent

Discharge of effluent into a
waterway can pose a health
threat to downstream users, since
disease-causing microorganisms
can be transmitted via water. Such
micro-organisms make water
unsafe for drinking or recreational
use.
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Management of
Dairy Farms
being irrigated
Effluent

Chemicals, such as pharmaceuticals
and cleaning agents, can act as
poisons to aquatic plants and
animals
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Best Practice
Management of
Dairy Farms
being irrigated
Effluent

The presence of effluent in New
Zealand’s waterways, and the
effect that it has, can upset local
residents and will give a poor
impression to overseas visitors.
Farm dairy discharges compromise
Maori cultural and spiritual values
(kaitiakitanga). Direct discharges
of treated or untreated effluent to
waterways are culturally offensive
to all New Zealanders.
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Best Practice
Management of
Dairy Farms
being irrigated
Effluent


Where effluent enters marine
environments it can have a
negative impact on shellfish
quality
Shellfish (such as mussels) are filter
feeders and accumulate the
microorganisms making them
unsuitable for human consumption.
This info from NZ Landcare Trust (see fact sheet)
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more?
Best Practice
Management of
Dairy Farms
being irrigated
Effluent – summary of effects
Implications
Social
Economic
•Recreational (swimming and trout fishing)
•Culturally offensive
Increased costs of water treatment for downstream
users
E-coli decreases aquaculture productivity (esp
shellfish)
Wasted nutrients that could be utilised on farm
Implications for NZ clean green image affecting
marketing of primary products and tourism.
Ecological Decreases oxygen content of water therefore
impacting on aquatic biodiversity.
Nutrients within effluent contribute to aquatic plant
and fungal slimes growth
Sediment
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Sediment may alter the colour, clarity or
temperature of a waterway. This can upset
aquatic ecosystems as well as reduce the
aesthetic value of the water.
Sediment will smother aquatic plants and
may reduce light infiltration, adversely
affecting plant photosynthesis.
Sediment can also smother insects on stream
beds and clog up the gills of fish.
Sedimentation of waterways can raise the
bed levels, causing flooding.
Sediments carry Phosphates (from fertilisers
and manure) into waterways which feeds
aquatic plant growth.
Nutrients



Ammonia-N is highly toxic to fish and aquatic
animals, even at low concentrations (i.e. 0.2 to 1.0
g/m3 ).
Ammonia-N requires large quantities of oxygen to
break it down. Therefore, ammonia breakdown
depletes the oxygen levels of waterways.
Nutrients such as N and P increase aquatic plant
growth, clogging waterways making water
unpleasant for swimming and drinking.



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Reducing stock losses
Bank errosion
Conserving soil
Improving stock health
Actions to Mitigate
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Dairy Farming and Water Quality