Case Study 1 - Darwin Harbour Water Quality

Discussion Paper: A Conversation with Territorians
Darwin Harbour Water Quality
Demonstration of
Strategic Policy
Priority 2: Foster water
Darwin Harbour supports
a range of ecosystems
including mudflats,
mangroves, and coral
reefs and seagrass, as
well as, animal life such as dolphins, dugong, sea
turtles, shorebirds, sponges and a large variety of
fish. These ecosystems rely, in part, on maintenance
of good water quality. In addition to natural values,
Darwin Harbour holds significant cultural, social
and economic value. Darwin Harbour is a working
harbour and developing into a major service centre
for the mining and energy sectors. Increases to
population, industry and development over time
will potentially increase pollution discharging to
waterways. Inputs to the Harbour from diffuse
sources (rainfall storm flow from the catchment) and
point sources such as discharge from waste water
treatment plants may result in increased pollutants
such as nutrients, sediments, metals and biological
Underpinning the water quality management of
Darwin Harbour is the declaration of the Harbour’s
beneficial uses under the Water Act. The beneficial
uses were first declared for Darwin Harbour in 1996,
and confirmed more recently following extensive
community consultation. The beneficial uses for
the Harbour’s saline waters are: aquaculture,
environment and cultural. The Harbour’s water
quality should be managed to ensure these uses are
protected. Protecting the declared beneficial uses
serves as a management goal.
To determine whether the beneficial uses are
being protected, the water quality of the harbour is
monitored. The monitoring results are compared to
declared water quality objectives which are specific
values (water quality concentrations).
If water quality exceeds these values this triggers
further investigation to determine if the water may be
polluted. The natural water quality of the Harbour is
highly variable due to the influence of the tides and
the suspension of mangrove muds and may account
for some values that exceed the objectives. The
results of the water quality monitoring are reported
annually in the Darwin Harbour Region Report Card,
supported by technical documents. A simple grading
of water quality, between A and E, is reported, where
A is excellent water quality and means water quality
is close to natural conditions.
Stewardship and protection of water quality is the
responsibility of all users and residents in the Darwin
Harbour region including Government. There are
many stakeholders who are undertaking, and hold
responsibility for actions, activities and management
measures that can impact either directly or indirectly
on water quality. A Water Quality Protection Plan
(WQPP) has been developed as a practical action
focused plan with more than 100 actions identified
to monitor, assess, manage and/or reduce nutrient
and sediment discharges and impacts to Darwin
The WQPP includes initiatives to reduce soil
erosion, minimise off-site sediment transport, protect
native vegetation alongside waterways, improve
management of wastewater and stormwater, reduce
runoff, remove or control potential pollutant sources,
improve the design and operation of infrastructure
and monitor potential environmental impacts. An
example of management action is the granting and
compliance assessment of waste discharge licences
issued under the Water Act. To minimise the impact
of discharges on beneficial uses, waste discharge
licences seek to control the quality and/or quantity of
pollutants entering a waterway, including nutrients.
The Chair of the Northern Territory Environment
Protection Authority assesses applications for waste
discharge licences and undertakes regulation and
compliance activities as a delegate of the Controller
of Water Resources.
The Darwin Harbour Water Quality Protection Plan
shows how legislation (Water Act) underpins the
management, how community input helped set
management objectives for water quality, the role
of monitoring checks whether the water quality is
satisfactory, and the Darwin Harbour Report Cards
inform the public. The actions of the Water Quality
Protection Plan highlight the many actions required
by several agencies and stakeholders to manage
Harbour water quality.
For further information, visit
For more information contact: Water Resources Division
P: 08 8999 4455 | E
: [email protected]