Australia Rivers

The river hydrography of the continent is of little importance. Most of it is characterized by the lack of superficial efflux (areic region according to the De Martonne nomenclature) or by internal drainage basins (endorheic region). Only on the northern and eastern coast is there a normal outflow or, as De Martonne defines it, exoreico. Since according to the said writer, the terms areic and desert are synonymous, almost half of Australia can be classified as desert. All the rivers usually indicated by the maps in the region run intermittently. The De Gray, Ashburton, Gascoyne and Murchison flow only after very heavy rains, and for long periods they are rivers in name only. The Gascoyne is 800km long, but is generally a dry wadi with pockets of water in the rocky sections; also the Fortescue has, at Millstream Station, a rocky bed where the water flows for a few kilometers, while elsewhere it is buried under thick gravel. Almost the same conditions occur in the long rivers marked on most maps as tributaries of Lake Eyre. The Finke, the Diamantina, and the Barcoo (or Cooper: 1620 km.) Are generally nothing more than sandy beds bordered by vegetation a little thicker than usual; but during the rare floods these the Diamantina, and the Barcoo (or Cooper: 1620 km.) are generally nothing more than sandy beds bordered by vegetation a little thicker than usual; but during the rare floods these the Diamantina, and the Barcoo (or Cooper: 1620 km.) are generally nothing more than sandy beds bordered by vegetation a little thicker than usual; but during the rare floods these creeks they can become rivers about thirty kilometers wide. Lake Eyre itself has never been observed in flood conditions, and a few months after the rivers have ceased flowing, no water can be seen from the shore at all. Halligan asserts that the area of ​​the lake in the period of maximum filling is 10,360 sq km, but the average area covered by the water cannot exceed 2500 sq km. Evaporation, according to Halligan’s calculations, generally consumes a greater quantity of water than that carried by the tributaries. Therefore this vast reservoir of salt water is rapidly drying up, and today its level is about 12 m. under that of the sea. Slightly smaller in size, Lake Torrens and the Gairdner (at 110 meters above sea level) are also quite vast salty ponds without emissaries, with strong fluctuations of level and surface and not infrequently reduced, in the dry periods, to expanses of mud and saline crusts dangerous for men and animals. An analogous ephemeral lake, which is assigned an area of 9000 sq. km., is Lake Amedeo, in the center of the Australian desert. These major lakes are accompanied by the numerous minor basins, already mentioned, which complete the picture of the residues of an ancient more humid regime, when, in the Tertiary and during the glacial period, the interior of Australia had flowing waters and on the the banks of its lake basins gathered a thick vegetation and a rich fauna, of which the fossilized remains are found in the ground. For Australia 2002, please check commit4fitness.com.

In the south-eastern part of the arid region flows the last stretch of the largest river in Australia: the Murray (1790 km.). Yet this too, several times, such as in 1914 and 1923, has ceased to flow. Its main tributary, the Darling (2450 km.), Crosses for most of its course the arid zone (areica), in which it lacks for. mostly every new contribution of water by tributaries; on the contrary, the flow of the river is decreasing due to evaporation. However, the Murray manages to maintain a range that allows for a certain navigability and small steamers can normally reach Echuca during the period July-January; on the Darling, on the other hand, navigation is very uncertain and during the last few years it has suffered long interruptions, up to eighteen months.

The rivers of the east coast are all short and steeply sloping. None of them matter for navigation. Only the lower reaches of the Hunter, Clarence and Richmond Rivers in New South Wales can be traversed by small vapors for about thirty kilometers. On the other hand, due to the coastal hills, even the longest rivers of Queensland, such as the Fitzroy and the Burdekin, are worthless for navigation: their lower course has a mountainous character; the most beautiful waterfalls in Australia are those of Barron (Cairns) 180 m high. More navigable are the main rivers of Northern Australia: small boats can go up the Victoria for 160 km. and the Daly for 110 km.; the Roper can be climbed for 150 km. from steamers that fish up to 4 m. The Fitzroy, in the Kimberley, has a course of 640km.

The unfavorable conditions of inland navigation are matched by the uniformity of the coastline, the lack of good natural ports on large stretches, the scarcity of joints. The marshy mangrove coasts of the Gulf of Carpentaria and the imposing bank of the Great Southern Bay make those two inlets of little use for landings. At both ends of the continent, the Torres Strait (80 km.) Which separates it from New Guinea and the Bass Strait (224 km.) Which intersects between it and Tasmania, have an ancient bad reputation for navigation. because of the innumerable, very dangerous rocks that emerge from the bottom, witnesses of the destroyed terrestrial bridges.

The west coast is flat and sandy and only in the north does it have any good ports (Port Darwin). Along the north-eastern coasts extend the shoals, the shallows, the cliffs of the Great Barrier Reef, now made safer by lighthouses and signals. The best landing conditions are found on the south-eastern coast where the two large gulfs of Spencer (with Port Pirie and Port Augusta) and S. Vincenzo (with Port Adelaide) and many other minor gulfs slip through, due to a phenomenon of lowering of the coast, which led the sea to invade the lower portions of the river valleys. Thus Port Phillip (in Melbourne) is due to the submergence of the Yarra River Valley and adjacent floors; Port Jackson (with Sydney) and Broken Bay, just north, are typical rias, i.e. submerged rocky valleys, which provide excellent natural harbors.

The overall island and coastal development of Australia is very limited. All the islands together, with Tasmania, do not exceed 85,000 sq km. surface; the coastal perimeter (19,700 km.) slightly exceeds the double of that of Italy.

Artesian waters. – While Australia is poor in perennial surface waters, it has a quantity of salient or artesian groundwater. greater than any other country. There are six separate basins, which together cover an area of ​​2 ½ million sq km. Of these the Great Artesian Basin, for the most part in Queensland, has an area of ​​over 1 ½ million sq km: it is bordered to the east by the main watershed of the eastern highlands, while to the west it includes the whole basin hydrographic of Lake Eyre and a great deal of that of Darling. This huge aquifer is found on average at a depth of 900 m, although a drilling near Longreach exceeds 2100 m. The basin is crossed by two buried ridges, one east of Cloncurry and another that runs north-east from Lake Eyre. The aquifers are mainly made up of porous sandstones from the Jurassic period. The water seems to derive mainly from the rains that fall on the eastern edge of the basin: it then slowly filters towards the west, finally flowing into hundreds of springs along the entire south-western edge of the artesian basin; it is quite salty, containing 0.0006 of salty residues, mostly sodium carbonate. There are presently some 1350 wells in Queensland and 530 in New South Wales, of very great value for cattle raising. However, the artesian waters are not used for cultivation. The Murray artesian basin is of much less importance for the saltiness of its waters, except in some districts such as at Pinnaroo. The Eucla basin and that of the desert (Broome) are little exploited; the narrow belt along the west coast supplies water to the northern pastoral farms and the city of Perth.