Gilbert-Einasleigh River
Encyclopedia
The Gilbert-Einasleigh River is one of the largest river systems in northern Australia
. It is located in north-central Queensland
, between the Flinders River
and the Mitchell River
.
, the Gilbert-Einasleigh has the sixth-highest discharge of any river in Australia, about equal to that of the Potomac
in North America. In a very wet "wet" season, however, the discharge can be as large as that of the Fraser River
in Canada, and in a dry "wet" like that of 1951/1952, the discharge can be as little as one tenth the long term mean. It is estimated that runoff from the Gilbert-Einasleigh system totals about 2.2 percent of the total runoff from Australia.
Both the Gilbert and Einasleigh Rivers rise in ancient uplands to the west of the Atherton Tableland
in northern Queensland. The two streams have their sources very close to each other but they begin by diverging as they flow into lower-lying country to the west, the Gilbert anticlockwise and the Einasleigh clockwise. Their almost circular flow takes them eventually together where they join almost due east of Normanton
and then flow in a west-northwesterly direction to the Gulf of Carpentaria. The only major tributary is the Etheridge River which joins the two main stems at a point very close to their convergence. From this point on, the river flows into a vast estuarine delta that largely consists of tidal flats and mangrove
swamp
s which flood during the "wet" season.
: in a wet season like 1973/1974 or 1999/2000 it can exceed 1800 millimetres (70.9 in), but in the almost nonexistent wet season of 1951/1952 it was as low as 300 millimetres (11.8 in) over much of the basin.
Because the river is much too erratic for hydroelectricity to be viable and the soils are exceedingly infertile - generally ironstone
gravels or kaolinitic clays - the Gilbert-Einasleigh is one of the relatively few completely free-flowing river systems of its size or greater in the world. Most of the basin is natural grassland used for grazing cattle
at the extremely low densities permissible with the very low nutritive qualities of the feed available: the population is no more than one thousand or one person for over 40 square kilometres. In the upper reaches soils are more fertile red cracking clays but erode too easily under the erratic rainfall for cropping to be a likely prospect even with groundwater
available. The mouth of the river lies in the Gulf Plains Important Bird Area
.
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. It is located in north-central Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
, between the Flinders River
Flinders River
The Flinders River is the longest river in Queensland, Australia at about . The river rises in the Burra Range, part of the Great Dividing Range, 110 km northeast of Hughenden and flows in a westerly direction past Hughenden, Richmond and Julia Creek then northwest to the Gulf of Carpentaria...
and the Mitchell River
Mitchell River (Queensland)
The Mitchell River is a river in the Far North Queensland region of Australia. The river begins on the Atherton Tableland about northwest of Cairns, and flows about northwest across Cape York Peninsula from Mareeba to the Gulf of Carpentaria....
.
Description
Although it is a seasonal stream and discharge can vary greatly depending on the intensity of the monsoonMonsoon
Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
, the Gilbert-Einasleigh has the sixth-highest discharge of any river in Australia, about equal to that of the Potomac
Potomac River
The Potomac River flows into the Chesapeake Bay, located along the mid-Atlantic coast of the United States. The river is approximately long, with a drainage area of about 14,700 square miles...
in North America. In a very wet "wet" season, however, the discharge can be as large as that of the Fraser River
Fraser River
The Fraser River is the longest river within British Columbia, Canada, rising at Fraser Pass near Mount Robson in the Rocky Mountains and flowing for , into the Strait of Georgia at the city of Vancouver. It is the tenth longest river in Canada...
in Canada, and in a dry "wet" like that of 1951/1952, the discharge can be as little as one tenth the long term mean. It is estimated that runoff from the Gilbert-Einasleigh system totals about 2.2 percent of the total runoff from Australia.
Atherton Tableland
The Atherton Tableland is a fertile plateau which is part of the Great Dividing Range in Queensland, Australia. It is located west to south-south-west inland from Cairns, well into the tropics, but its elevated position provides a climate suitable for dairy farming. It has an area of around...
in northern Queensland. The two streams have their sources very close to each other but they begin by diverging as they flow into lower-lying country to the west, the Gilbert anticlockwise and the Einasleigh clockwise. Their almost circular flow takes them eventually together where they join almost due east of Normanton
Normanton, Queensland
-External links:****...
and then flow in a west-northwesterly direction to the Gulf of Carpentaria. The only major tributary is the Etheridge River which joins the two main stems at a point very close to their convergence. From this point on, the river flows into a vast estuarine delta that largely consists of tidal flats and mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
swamp
Swamp
A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...
s which flood during the "wet" season.
Environment
The climate of the basin is tropical, with annual rainfall generally around 800 millimetres (31.5 in). Almost all the annual rainfall occurs between December and March: the months from May to September are rainless in over 60 percent of years (over 80 percent for August). Rainfall is highly variable due to monsoon variability and occasional severe cyclonesTropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
: in a wet season like 1973/1974 or 1999/2000 it can exceed 1800 millimetres (70.9 in), but in the almost nonexistent wet season of 1951/1952 it was as low as 300 millimetres (11.8 in) over much of the basin.
Because the river is much too erratic for hydroelectricity to be viable and the soils are exceedingly infertile - generally ironstone
Ironstone
Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical repacement, that contains a substantial proportion of an iron compound from which iron either can be or once was smelted commercially. This term is customarily restricted to hard coarsely...
gravels or kaolinitic clays - the Gilbert-Einasleigh is one of the relatively few completely free-flowing river systems of its size or greater in the world. Most of the basin is natural grassland used for grazing cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
at the extremely low densities permissible with the very low nutritive qualities of the feed available: the population is no more than one thousand or one person for over 40 square kilometres. In the upper reaches soils are more fertile red cracking clays but erode too easily under the erratic rainfall for cropping to be a likely prospect even with groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
available. The mouth of the river lies in the Gulf Plains Important Bird Area
Gulf Plains Important Bird Area
The Gulf Plains Important Bird Area comprises 8868 km2 of the low-lying coastal plains bordering the south-eastern corner of the Gulf of Carpentaria in north-west Queensland, Australia...
.