IN THIS SECTION
The Mitchell River Catchment
History
Activities
Climate
Fauna & Flora
Bio-physical aspects
Management issues
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The Mitchell River Catchment
The Mitchell River catchment in Tropical North Queensland, Australia, spans 72,000 square kilometres (the size of Tasmania) across the base of Cape York Peninsula. It incorporates five major river systems: the Mitchell, Alice, Palmer, Walsh and Lynd, and involves four local governments; namely Mareeba, Cook, Carpentaria and Kowanyama Communities Local Government Area.

History
The main reason Europeans moved into the Mitchell River Catchment area in the late 1800s was mining, in particular gold. There were numerous battles between the Aboriginal peoples and the Europeans and this is reflected in the names of many localities, such as Battlecamp Road. Once the miners moved into an area there was an associated increase in demand for support services such as food provision. This therefore meant that graziers would follow the miners into a new area to provide this service, resulting in the use of the land for agriculture.

Activities
Grazing remains the most extensive land use in the catchment area whilst mining activities are making a resurgence due to high base metal prices. The Mareeba Dimbulah Irrigation Scheme established in the 1950's has also made the upper catchment of the Mitchell and Walsh Rivers viable for agriculture, horticulture and small scale cattle fattening projects. Furthermore, tourism and fishing have risen in prominence in recent years.

The Mitchell River Catchment area consists of mainly large grazing leases, although the exceptions to this are the Kowanyama Aboriginal Community DOGIT (Deed Of Grant In Trust) and the freehold areas of Southedge Station, part of Wrotham Park Station and many smaller blocks in the East of the catchment. Indigenous people own several holdings in the catchment, including Kondaparinga, Bulimba, Bonny Glen, Oriners, Powis and Sefton.

The Catchment area also contains the following National Parks:
- Hann Tableland National Park Mitchell
- Alice Rivers National Park
- Chillagoe-Mungana Caves National Park
- Part of Bulleringa National Park to the South
- Most of the 40 Mile Scrub National Park

Climate
The climate is tropical and monsoonal with ninety-five percent of the mean annual rainfall of between 800 mm and 2000 mm occurring from November to April. The Mitchell Catchment is the largest watershed in Queensland in terms of average annual run-off, with a mean discharge of nearly 12,000,000 megalitres.

Fauna & Flora
The vegetation in the Mitchell River Catchment area ranges from the World Heritage Wet Tropic rainforest on the eastern highlands to the open savannah on the western and lower Mitchell plains. The extensive mangroves and lagoon systems at the delta of the Mitchell River are recognised worldwide. The permanent waters in the upper catchment are associated with springs and water holes and much of the catchment overlays the Great Artesian Groundwater Province.

Few comprehensive biological and ecological studies have been undertaken in the catchment area to date. However, it is known that eighteen species of animal classified as rare, vulnerable, or endangered, including the Golden Shouldered Parrot, the Gouldian Finch and the Northern Bettong are known to occur in the catchment. The inshore islands of the Gulf of Carpentaria also harbour a rich variety of marine life, including turtles and dugong. The Mitchell River, though poorly studied, may possibly contain the most ecologically diverse aquatic system in the country, reflecting the rich variety of habitats in a large river system with wet tropics, dry tropics and monsoonal influences.

Bio-physical aspects
The Mitchell River catchment occupies an area across both the Einasleigh Uplands and Gulf Plains bioregions and abuts the Cape York Peninsula bioregion on its northern boundary. The river and its tributaries have long been carving through the rough and weathered highlands in the east of the catchment, depositing sediments on the broad flood plains and wetlands of the Gulf Savannah. The annual monsoonal wet season provides a pulse of water that transports sediments, organic matter, and, unfortunately, chemical residues from agriculture and mining in the catchment and, for a time, links the terrestrial and marine environments. It is this seasonal pulse of water that provides the major connection between different resource uses, as well as connecting the various communities within the Mitchell River Catchment area. It also allows for the migration of many plants and animals, both native and feral, whether a beneficial or a nuisance species, as well as shaping the land.

The Mitchell River Catchment are also contains tropical rainforest, wet sclerophyll forest, a variety of woodland types, savannah, tidal plains, as well as extensive wetlands, estuaries, and mangroves.

Eastern Highlands
The landforms in the Eastern Highlands are dominated by hills and mountains of sedimentary and metamorphic rock with numerous creeks and seasonal drainage systems making very rugged country.

Central Uplands
This region is mostly undulating country, underlain by metamorphic and granitic rocks. Rock outcrops of a similar but older type also occur in a belt throughout the centre of the area.

Western Plains
These plains form the bridge between the high country to the east and the floodplains to the west with a thick bed of sediments laid down in the Tertiary period dominating the area.

Lower Mitchell Plains
This is a huge floodplain which includes virtually the whole area where the main tributaries join the Mitchell River. It consists of alluvial sands, silts and clays which have collected near sea level.

Coastal Plains
These occupy a small area along the coast of the Gulf of Carpentaria and consist of recently deposited marine and land sourced clays and sands.

Management issues
Water quality
The Mitchell River Catchment is a very large area affected by the monsoonal wet and dry seasons. In the dry season many rivers cease to flow, which highlights the value of, and the need for management of, perennial creeks and waterholes in the catchment. Part of the Mareeba-Dimbulah Irrigation Area is within the Mitchell River Catchment and receives water from both Lake Tinaroo and the Walsh River. Of increasing concern is that the pest fish Tilapia could escape from Lake Tinaroo and make its way into the Mitchell River Catchment. This pest could severely impact on the environment as well as recreational and commercial fishing industries in the Gulf of Carpentaria. Tilapia exclusion screens have been installed in the irrigation channels to minimise the risk of this happening. The intensification of agricultural crops in the irrigation area coupled with inappropriate irrigation practices could also impact on water issues in the catchment.

Land degradation
There are many forms of land degradation, but the most common in the Mitchell River Catchment is accelerated erosion as much of the area has very fragile soils with low fertility and minimal groundcover. These areas erode readily if the surface vegetation is disturbed by either natural events, such as flooding and associated streambank erosion, or problems caused by grazing pressure and the associated spread of weeds.

Weeds
A wide range of weeds, with both economic and environmental implications, have gained a foothold in the Mitchell River Catchment. Rubbervine was considered to be the greatest threat to large areas of the catchment, but is being displaced by bellyache bush (Jatropha gossypiifolia) in two known areas. Bellyache bush is a weed species from tropical America that blankets out native species and has poisonous berries that have killed cattle eating it in the absence of other feed. Prickly acacia, chinee apple, parkinsonia, Giant Rats Tail Grass and many other pest plants are also commonly found in the catchment. Aquatic weeds such as salvinia, hyacinth and cumbungi are also threats to the Mitchell's waterways and aquatic ecosystems. There is a need for improved coordination and cooperation amongst the community to control and manage these weeds.

Nature Conservation
The Mitchell River Watershed is home to a large diversity of flora including rainforest, eucalypt forest and woodland, savannah, wetlands, dunes and mangroves. Only some areas of the catchment have been intensively studied, and there is little recorded information on much of it to use in catchment planning. There is a sizeable reserve of protected areas in the catchment and the Wet Tropics World Heritage Area fringes the catchment in the Eastern highlands. The Mitchell-Alice, Chillagoe/Mungana Caves and the Hann Tableland are all notable National Parks in the Mitchell River Catchment
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Conservation areas cannot be declared everywhere, nor should conservation interests be restricted to parks only. All land management decisions should include consideration of nature conservation aims, incorporating set standards to protect and enhance the existing environmental values and ecosystem services of the land.

Fire Management
Fire in the Mitchell River catchment is an integral part of the ecosystem with most vegetation communities adapted to, and modified by, the frequency of fire. Fire will occur whether lit naturally, accidentally, negligently or deliberately. The vegetation communities of woodland and eucalypt forest are both susceptible and adapted to fire, whilst the climatic conditions of Australia are conducive to the propagation and spread of fire. Firebreaks are a necessity where fire could spread to areas where burning is not wanted. Removal of dead plant material that could fuel a fire and the promotion of green vegetation or the use of fire resistant trees are effective firebreak methods in small acreage areas, especially on sloping land.

Fire frequency is often a question of social response versus safety needs and fire management is for life, property and environment - but which takes precedence is often debated. Recent studies have suggested that poorly timed back burning may have a detrimental effect on certain types of vegetation, even creating conditions that may encourage the spread of weed species, and has a negative impact on the animals that rely on the suppressed native vegetation as feed or habitat.

For more information on fire management go to the Fire North website. Check out the web site link that gives you access to current fire hotspot information and lots more.

Intensive Agriculture
Although intensive agriculture is a commercially significant land use in the Mitchell River catchment, it represents less than two percent of the total catchment area. It is mainly limited to the Upper Walsh portion of the Mareeba-Dimbulah Irrigation Areas (MDIA) and the Upper Mitchell Catchment north of Mareeba at Biboohra, Julatten and Maryfarms. Intensive agriculture can impact on its surrounding environment and downstream waterways in several ways.

Land clearing, for example, can sometimes increase erosion and reduce wildlife habitat and cause changes to catchment hydrology through water extraction, changes in vegetation cover, and the addition of irrigation water. Potential also exists for serious environmental damage to water quality and aquatic ecosystems through poor management of farm chemicals and fertilisers. Many of these potential impacts can be reduced through sound planning and developing the capability to recognise and address a variety of management needs to protect and enhance the existing environmental values and ecosystem services of the catchment.

Grazing Management
Grazing is the most extensive land use in the catchment and properties tend to be large, with low intensity management.  Much of the grazing lands in the Mitchell are nutrient poor and soil fertility is greatest on river frontages and floodplains, making these areas of high value, both to graziers and for their biodiversity and ecosystem services. A key element of sustainable land use could be to consider grazing on river banks and flats as a last resort in hard times, as their continual use can too readily degrade these key areas of the aquatic ecosystem. The environmental impacts of grazing in the Mitchell cannot be attributed to any single factor and cattle are attracted to virtually all permanent waters in the Mitchell.

Pasture, ground cover and fuel loading can decline over large areas due to grazing pressure and in turn these can be contributing factors to weed and land degradation problems. Road and track networks to service the industry can often lead to erosion problems. Many of these issues can only be addressed in the context of property management planning that considers not only stock management needs but also sustainable land use and maintenance of the existing environmental values and ecosystem services of the land.

Fisheries Management
The Mitchell River is a rich fisheries resource and valued species for commercial and recreational fishing found in this catchment include barramundi, salmon, grunter and crab. The Coleman River and North Mitchell River are also nursery grounds for commercially fished prawn species, particularly the banana prawn.

The Mitchell River provides an important and varied food resource for indigenous people as well as making a significant contribution to the development of the commercial fishing industry in Karumba. A growing number of recreational fishermen are also now sharing in the fishery resources of the Mitchell River Catchment area. These fishery resources could be under threat from the pest fish Tilapia if it establishes itself in the Mitchell River Catchment. There has also been little information gathered for sound management of the Mitchell's fisheries. Necessary fisheries management information should include reports on sustainable fisheries harvest, requirements that would require studies of the various fish populations and their respective abilities to sustain specific harvest levels.

Feral animals
Several feral animal species now make their home in the Mitchell River Catchment area and includes pigs, cane toads, horses, cats, dogs & some species of fish.  Landholders have a responsibility to control their numbers as some of these feral animals are declared under the Rural Lands Protection Act 1985.

The impacts of feral animals vary between species and the local environment. In selected areas some feral animals have become valued resources, but in most areas feral animals are at best a nuisance and at worst a serious economic and environmental threat. Strategies for feral animal management must consider many factors if they are to be cost effective and worthwhile but without baseline information, feral animal control strategies are difficult to formulate. Current information on feral animal distribution is sketchy and very poorly documented. Collecting information on most feral animal species is difficult because the Mitchell River Catchment is large and sparsely populated by humans, therefore, there is little information available to base any scientific research on.

Tourism and recreation
Many areas of the Mitchell River Watershed are used for Tourism and Recreation. From the mouth in the Gulf of Carpentaria to the mountain ranges of the Wet Tropics, the catchment is under increasing pressure from recreational activities. Many of these activities occur on land that is not designated or supported for tourism and recreational use.

The access provided by four-wheel drives, trail bikes and quad bikes to previously inaccessible areas of the catchment has created an increasingly popular recreational use that is particularly difficult to manage. Four-wheel drives offer self-contained travel, often producing little economic benefit to areas being visited. Road improvements on the Cape and Burke Developmental Roads are now allowing greater numbers of people in standard vehicles to access the catchment. Management problems including fires, rubbish, access disputes, weed dispersion, water pollution and site impacts from camping and rest areas (commonly in riparian zones), and public safety issues and will ultimately increase as visitor numbers rise. Access to the recreational resources of the Mitchell is important to a large, but hard to identify, segment of catchment stakeholders and land use and management planning must recognise and account for this.

Mining
Mining is a significant industry in the Mitchell River catchment. It is the oldest non-aboriginal land use in the catchment, being a significant activity in the region for more than 120 years. However, with the benefits have come some costs. The social cost of early mining operations is highlighted by boom-and-bust towns, such as Maytown, Irvinebank and Chillagoe, the battles between the aboriginal peoples and the miners on many goldfields, and the mine explosion disaster at Mt Mulligan Mine.

Despite early setbacks, not the least of these being the remoteness of much of the region, mining has flourished and remains a significant industry in some areas of the catchment. Small scale alluvial and hardrock gold and tin operations have dominated mining activities in recent times. However, increases in some metal prices have led to an increased interest in other mineral deposits and large-scale mining may commence, or recommence, in some parts of the catchment.

Historic mining and mineral processing sites may have many special land management issues due to the presence of site contamination from mining residues and other pollutants. The condition of these sites is the result of an era in which winning minerals was paramount and environmental damage was not a consideration. Whilst such environmental damage would never be acceptable today, historic mining works are an important element of the cultural history of many communities.

Cultural Heritage
Cultural heritage (both European and Aboriginal) can be a deeply emotive issue that provides knowledge of our ancestry and a sense of belonging for many people. Cultures have clashed violently in the Mitchell River Catchment area in the past, but planning for a sustainable future for the catchment can only be based on mutual recognition of, and respect for, the values, especially environmental and cultural, of all the communities living in the area. There are many documented heritage sites within the catchment and the non-indigenous sites are mostly found within and around old mining centres, such as Chillagoe, Irvinebank, Mt Carbine and Maytown.

Most of the formally recorded Aboriginal sites also occur near these mining centres and include shelters, rock art and utilitarian evidence of indigenous inhabitants. The distribution of recorded Aboriginal sites near mining centres perhaps reflects the fact that discovery of sites by Europeans is more likely to have occurred around areas of intensive European activity. No doubt many more sites exist unrecorded, and maybe even unknown, in areas cleared of their aboriginal peoples by miners and graziers. Cooperative management provides the best avenue to ensure that all cultural heritage is retained. Information about local cultural heritage is being collected and children are being involved in school programs to ensure the passing on of this information.

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Common Dunnart with pouch young
Photo: Scott Burnett
















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