How big is the Fitzroy Basin?
The Fitzroy Basin is the second largest catchment in Australia,
including one of the largest river systems culminating in the
mighty Fitzroy River in Rockhampton. It’s about 150,000
square km in size - that’s the size of Tasmania plus 80,000
km2 to spare!
The catchment includes several major tributaries:
Nogoa River:
starts about 200km south-west of Emerald, fills the Fairbarn Dam
and is joined by Theresa Creek from the north.
Comet River:
flows through the south-east of the central highlands parallel to
Springsure to meet the Nogoa. The system is then called the
Mackenzie.
Mackenzie:
flows through the middle of the basin from above Blackwater, winds
north to Middlemount and is then joined by the Isaac.
Isaac River:
source is at the upper reaches of the catchment north of Moranbah,
and include the Connors river flowing from the western side the
range just behind Sarina.
Dawson:
around one third of the Fitzroy, the Dawson’s source is near
Injune at the southern most reach of the catchment, flows through
Taroom, Theodore and Baralaba before meeting the Mackenzie. When
the Mackenzie and Dawson come together, the river is called the
Fitzroy.
Water that flows through the rivers and streams of the Fitzroy
Basin all connect eventually with the Fitzroy River, which flows
out to the Great Barrier Reef Lagoon. The map on the opposite page
shows the many waterways that make up this massive river system.
Why does the Fitzroy take so long to peak?
All in all, more than 20,850km of waterways wind through the basin
to drain into the Fitzroy River. From the headwaters of either the
Nogoa or Dawson River to the mouth of the Fitzroy River, water must
travel more than 750km across the basin, which means it can take
several days for the water to reach Rockhampton.
Why and when does it flood?
The region’s rainfall is highly variable. Long dry spells are
often followed by intense wet season rainfalls. Due to its extreme
size and fan-like shape, the Fitzroy Basin is capable of producing
large flooding. The highest recorded flood occurred in 1918, which
was 10.11m. Please see graph on fact sheet for more records.
What does it mean for the environment?
Floods are a natural phenomenon and can have both positive and
negative impacts on the environment.
The Fitzroy has one of the most extensive natural coastal
floodplains on the east coast of Australia. Floodplains line the
major streams, rivers and delta of the Fitzroy Basin and act as
sediment sinks.
This helps reduce the amount of dirt and contaminants that reach
the ocean and delicate reef ecosystems. The Fitzroy River mouth
marks the beginning of the Great Barrier Reef World Heritage Area.
Flood plumes discharged from large floods inundate Keppel Bay,
which is home to reefs with some of the highest coral cover, and
extend east across the Capricorn Bunker Group and north of Townsend
Island, covering an area greater than 10,000 square km.
However, fresh water flowing to the ocean is not wasted. The
Fitzroy Basin is one of the state’s most significant fish
nurseries and floods can assist in the spawning of native fish
including barramundi. After the 1991 flood, tagged barramundi were
found around 1000km of coastline from Hervey Bay to Mackay, showing
that infrequent large flows aid in the maintenance of strong
genetic diversity for the region’s fisheries.
