What is a catchment?

A river catchment, or drainage basin, is all the land drained by a single river and its tributaries, usually from a high point (hill, mountain) to a low discharge point (wetland, lake, sea). A large catchment may incorporate a number of smaller sub-catchments.

Barron Falls

Catchment Details

locationMap.pngThe Barron River Catchment covers an area of 2,100 km2 (or 226,000 hectares), is over 165 km long and is one of ten catchments in the Wet Tropics NRM Region of North Queensland.

 

Twenty percent of the catchment is included in the Wet Tropics World Heritage Area. The catchment is unique because of the contrasts in climate, the diversity of soils, the number of rare and threatened plant and animal species, and the range of land uses.

 

Within the catchment the major land uses are mixed cropping, horticulture, grazing, forestry, sugar, world heritage and urban and tourist development.

 

For a more detailed image of the Barron River Catchment - See Map Here

 

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Physical features

Half of the catchment – the eastern and northern areas – features mountain ranges of granite and metamorphic rocks clothed in rainforest and wet sclerophyll forest. The southern quarter is the flat and undulating land of the deeply weathered basaltic Atherton Tableland plateau. The remaining western quarter is flat to undulating savannah on metamorphic, alluvial and volcanic rocks.

 

Climate

Like all catchments in the Wet Tropics, the Barron River receives high rainfall in the summer monsoon, and lighter falls throughout the remainder of the year. Annual rainfall varies from over 2500mm in the upper catchment (or higher in the Lamb Range), through 900mm in drier parts of the middle catchment, to 2000mm on the coastal plain.

Long-term annual totals: Atherton – 1380.9mm; Mareeba – 926.9mm; Cairns – 2005.2mm

 

Hydrology

The main characteristic of the Barron catchment is the dense fine network of small streams. The Barron River itself originates on the upland ranges of the Atherton Tablelands at Mt Hypipamee National Park, at an altitude of about 1000m. Other small streams originate in rainforest and run through forest or farmland to meet the main stream of the Barron. Wetlands of national significance in the upper catchment include Lake Barrine, Lake Eacham, Lake Euramoo and the Crater Lakes.


Twenty kilometres downstream from its source, the Barron River drains into Tinaroo Falls Dam. At this point the hydrology of the catchment is highly modified. Flows from the dam are controlled by outlet valves to the river and to irrigation channels of the Mareeba-Dimbulah Irrigation Area (MDIA), and the spillway. The mean annual discharge of the Barron catchment is 990,000 megalitres, which calculates as 37% of the incident rainfall over the catchment. This is a low discharge figure when compared with the values of 59% to 74% for other less modified rivers in the Wet Tropics (Barron River Catchment Management Plan 2004).

 

The middle reaches, 300-700 metres above sea level, include streams originating in rainforest, and sparser drainage from farmland and savannah sources.

 

The river plunges 260 metres down the Barron Falls Gorge to the alluvial plain below, and flows through farmland and urban landscapes to the delta and estuary north of Cairns. Important wetland systems on the floodplain – habitat for  commercial fish species and  migratory wading birds – include swamp forests and lagoons, with mangroves, intertidal wetlands and saltmarshes on the coastal part of the delta.

 

Vegetation

The Barron River catchment is the most extensively modified of all the wet tropics catchments. The  original vegetation, much of it rainforest, has been cleared on the basalt soils of the Atherton Tableland and the alluvia of the coastal plain, and replaced by a variety of crops, including potatoes, peanuts, maize, fruits and sugarcane together with dairy and beef cattle pasture. The completion of Tinaroo Falls Dam in 1958 permitted agricultural expansion into the central and western sections and beyond into the neighbouring Walsh/ Mitchell Catchment within the Mareeba-Dimbulah Irrigation Area. Forest plantations of Hoop and Caribbean Pine are extensive around Lake Tinaroo in Danbulla State Forest and north of Kuranda.

 

Most of the remaining natural vegetation of the catchment consists of various types of open eucalypt forest and woodland. Rainforest vegetation is now confined to parts of the upper catchment and along the eastern rim. 

 

Life under threat 

 

Plants

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Due to extensive clearing within the catchment, several of the original vegetation types are classified as endangered or vulnerable to extinction. The endangered communities are the focus of revegetation activities by Barron Catchment Care.


Endangered communities

  • Upland complex notophyll vine forest - type 5b of Tracey (1982)   – Mabi rainforest

  • Notophyll vine forest with emergent wattles on moist to dry coastal lowlands and foothills (types 7a, 7b)

  • Tiny patches of mesophyll vine forest on calcareous beach sands of the delta and northern beaches (type 2b)

  • Tall open eucalypt (wet sclerophyll) forests of the upper catchment (type 14c).

Communities vulnerable to extinction

  • Mesophyll vine forest with dominant feather and fan palms (types 3a, 3b respectively)

  • Tall open forests/ woodlands on the basalts of the upper catchment (types 14a, 14b).

More than 125 plant species found in the Barron Catchment are officially listed as rare/ threatened in Schedules of the Wildlife Regulations of the Nature Conservation Act (1992). The rainforests of the basaltic uplands, in particular, contain unusually high concentrations of rare and restricted species. The remnant forest patches of the coastal plain and adjoining foothills also support several rare/ threatened species.

 

Animals

The fauna of the Wet Tropics bioregion is extremely diverse (approaching 600 vertebrate species), with a number of species confined to the region (endemic). Most of the endemic species are dependent on the upland rainforests, now greatly reduced in area, fragmented or weed-infested. The Barron Catchment spans the entire width of the Wet Tropics bioregion and touches on the drier Einasleigh Upland and southern Cape York Peninsula bioregions, which explains the variety of animals within the catchment.

 
Notable animal occurrences in the Barron Catchment are:

 

  • 10 of the 11 Wet Tropics endemic animals

  • All 13 species and 10 sub-species of regionally endemic birds

  • Several endangered bird species, including small populations of the Australia's largest bird, the Southern Cassowary (Casuarius casuarius johnsoni)

  • Several critically endangered frog species

  • Remaining populations of Lake Eacham Rainbowfish (Melanotaenia eachamensis) in some tableland streams.


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Found nowhere else

Ten of the 11  Wet Tropics endemic mammals occur in the Barron catchment:

  • Green Ringtail Possum (Pseudochirops archeri)

  • Herbert River Ringtail Possum (Pseudochirulus herbertensis)

  • Lemuroid Ringtail Possum (Hemibelideus lemuroids)

  • Northern Bettong (Bettongia tropica)

  • Lumholtz Tree-kangaroo (Dendrolagus Iumholtz)

  •  Musky Rat-kangaroo (Hypsiptymnodon moschatus)

  • Atherton Antechinus (Antechinus godman)

  •  Long-tailed Pygmy-possum (Cercatetus caudatus)

  • Prehensile-tailed Rat (Pogonomys mollipilosus) 

  • Tube-nosed Bat (Murina florium)

...and one from the Einasleigh Upland bioregion, on the Barron catchment's western margin:

  • Mareeba Rock-wallaby (Petrogale mareeba)
Green Possum endemic to the area

      Green Ringtail Possum (Pseudochirops archeri)

The natural and human activities that occur in a catchment area affect the physical, chemical and biological characteristics of the river.

 

In a catchment area, everything and everybody is linked by water. What happens in one part of the catchment can affect the wellbeing of the rest of the catchment area. For example, an upstream soil erosion problem may lead to siltation problems downstream and affect the health of the river as well as the reef at the endpoint.

 

A catchment area is therefore a useful planning unit for natural resource management.