In ecology, an oasis is a fertile area of a desert or semi-desert environment that sustains plant life and provides habitat for animals. Surface water may be present, or water may only be accessible from wells or underground channels created by humans. In geography, an oasis may be a current or past rest stop on a transportation route, or less-than-verdant location that nonetheless provides access to underground water through deep wells created and maintained by humans. Although they depend on a natural condition, such as the presence of water that may be stored in reservoirs and used for irrigation, most oases, as we know them, are artificial.
The Namib is a coastal desert in Southern Africa. According to the broadest definition, the Namib stretches for more than 2,000 kilometres (1,200 mi) along the Atlantic coasts of Angola, Namibia, and northwest South Africa, extending southward from the Carunjamba River in Angola, through Namibia and to the Olifants River in Western Cape, South Africa. The Namib's northernmost portion, which extends 450 kilometres (280 mi) from the Angola-Namibia border, is known as Moçâmedes Desert, while its southern portion approaches the neighboring Kalahari Desert. From the Atlantic coast eastward, the Namib gradually ascends in elevation, reaching up to 200 kilometres (120 mi) inland to the foot of the Great Escarpment. Annual precipitation ranges from 2 millimetres (0.079 in) in the aridest regions to 200 millimetres (7.9 in) at the escarpment, making the Namib the only true desert in southern Africa. Having endured arid or semi-arid conditions for roughly 55–80 million years, the Namib may be the oldest desert in the world and contains some of the world's driest regions, with only western South America's Atacama Desert to challenge it for age and aridity benchmarks.
A dry lake bed, also known as a playa, is a basin or depression that formerly contained a standing surface water body, which disappears when evaporation processes exceed recharge. If the floor of a dry lake is covered by deposits of alkaline compounds, it is known as an alkali flat. If covered with salt, it is known as a salt flat.
In Australian English, a billabong is a small body of water, usually permanent. It is usually an oxbow lake caused by a change in course of a river or creek, but other types of small lakes, ponds or waterholes are also called billabongs. The term is likely borrowed from Wiradjuri, an Aboriginal Australian language of New South Wales.
The Lake Eyre basin is a drainage basin that covers just under one-sixth of all Australia. It is the largest endorheic basin in Australia and amongst the largest in the world, covering about 1,200,000 square kilometres (463,323 sq mi), including much of inland Queensland, large portions of South Australia and the Northern Territory, and a part of western New South Wales. The basin is also one of the largest, least-developed arid zone basins with a high degree of variability anywhere. It supports only about 60,000 people and has no major irrigation, diversions or flood-plain developments. Low density grazing that sustains a large amount of wildlife is the major land use, occupying 82% of the total land within the basin. The Lake Eyre basin of precipitation to a great extent geographically overlaps the Great Artesian Basin underneath.
Colorado Desert is a part of the larger Sonoran Desert located in California, United States, and Baja California, Mexico. It encompasses approximately 7 million acres, including the heavily irrigated Coachella, Imperial and Mexicali valleys. It is home to many unique flora and fauna.
The Paroo River, a series of waterholes, connected in wet weather as a running stream of the Darling catchment within the Murray–Darling basin, is located in the South West region of Queensland and Far West region of New South Wales, Australia. It is the home of the Paarkantji people.
An arroyo, from Spanish arroyo, also called a wash, is a dry watercourse that temporarily or seasonally fills and flows after sufficient rain. Flash floods are common in arroyos following thunderstorms. It's akin to the Catalan rambla, which stems from the Arabic rámla, "dry river".
A ciénega is a wetland system unique to the American Southwest and Northern Mexico. Ciénagas are alkaline, freshwater, spongy, wet meadows with shallow-gradient, permanently saturated soils in otherwise arid landscapes that often occupy nearly the entire widths of valley bottoms. That description satisfies historic, pre-damaged ciénagas, although few can be described that way now. Incised ciénagas are common today. Ciénagas are usually associated with seeps or springs, found in canyon headwaters or along margins of streams. Ciénagas often occur because the geomorphology forces water to the surface, over large areas, not merely through a single pool or channel. In a healthy ciénaga, water slowly migrates through long, wide-scale mats of thick, sponge-like wetland sod. Ciénaga soils are squishy, permanently saturated, highly organic, black in color or anaerobic. Highly adapted sedges, rushes and reeds are the dominant plants, with succession plants—Goodding's willow, Fremont cottonwoods and scattered Arizona walnuts—found on drier margins, down-valley in healthy ciénagas where water goes underground or along the banks of incised ciénagas.
A guelta is a pocket of water that forms within rock formations in the Sahara Desert and Arabian Desert. The term is of Arabic origin and specifically refers to oases that emerge in rocky landscapes in Arab regions, particularly in countries like Algeria and Saudi Arabia.
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface. Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally and through anthropogenic processes, where rainwater and/or reclaimed water is routed to the subsurface.
The Swakop River is a major river in western central Namibia. Its source is in the Khomas Highland. From there it flows westwards through the town of Okahandja, the historic mission station at Gross Barmen, and the settlement of Otjimbingwe. It then crosses the Namib desert and reaches the Atlantic Ocean at Swakopmund. The Swakop is an ephemeral river; its run-off is roughly 40 million cubic metres per annum.
Wild Africa is a British nature documentary series created and produced by the BBC. It explores the natural history of the African continent. It was first transmitted on 7 November 2001 on BBC Two in the United Kingdom and comprises six episodes. Each concentrates on a particular environment. The producers use aerial photography and wildlife footage to show how natural phenomena such as seasonal changes influence the patterns of life. Wild Africa was produced by the BBC Natural History Unit and narrated by Fergal Keane.
A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the land surface of the Earth is arid or semi-arid. This includes much of the polar regions, where little precipitation occurs, and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location.
The Paroo-Darling National Park is a protected national park that is located in the Far West region of New South Wales, in eastern Australia. The 178,053-hectare (439,980-acre) national park spans two distinct regions in the outback area. This region covers the arid catchments of the Paroo River and the Paroo-Darling confluence to the south.
Biogeographic classification of India is the division of India according to biogeographic characteristics. Biogeography is the study of the distribution of species (biology), organisms, and ecosystems in geographic space and through geological time. India has a rich heritage of natural diversity. India ranks fourth in Asia and tenth in the world amongst the top 17 mega-diverse countries in the world. India harbours nearly 11% of the world's floral diversity comprising over 17500 documented flowering plants, 6200 endemic species, 7500 medicinal plants and 246 globally threatened species in only 2.4% of world's land area. India is also home to four biodiversity hotspots—Andaman & Nicobar Islands, Eastern Himalaya, Indo-Burma region, and the Western Ghats. Hence the importance of biogeographical study of India's natural heritage.
Yapunyah Waterhole lies in the Mulga Lands bioregion of western Queensland. The waterhole is about two kilometres long and covers approximately 22 hectares when full. It is defined as a permanent waterhole in a region where permanent waterholes are extremely rare and therefore provide important refuges for aquatic plants and animals. These rare waterholes were also vital for Aboriginal people and provided both spiritual and physical nourishment.
The Hoanib is one of the 12 ephemeral seasonal rivers in the west of Namibia, where it used to be the border between northern Damaraland and Kaokoland. Its length is 27 kilometres (17 mi). With the low population density in the area, the oasis character of the river valley and the relatively high wildlife population of the Hoanib, like in the case of the Hoarusib, its valley is one of the last true wilderness areas in Namibia. One of the last settlements of desert elephants, it is characterised by strong wind and water eroded, weathered stone deposits. Inflows of Hoanib are Aap River, Otjitaimo River, Ombonde, Ganamub, Mudorib and Tsuxub.
Tropical deserts are located in regions between 15 and 30 degrees latitude. The environment is very extreme, and they have the highest average monthly temperature on Earth. Rainfall is sporadic; precipitation may not be observed at all in a few years. In addition to these extreme environmental and climate conditions, most tropical deserts are covered with sand and rocks, and thus too flat and lacking in vegetation to block out the wind. Wind may erode and transport sand, rocks and other materials; these are known as eolian processes. Landforms caused by wind erosion vary greatly in characteristics and size. Representative landforms include depressions and pans, Yardangs, inverted topography and ventifacts. No significant populations can survive in tropical deserts due to extreme aridity, heat and the paucity of vegetation; only specific flora and fauna with special behavioral and physical mechanisms are supported. Although tropical deserts are considered to be harsh and barren, they are in fact important sources of natural resources and play a significant role in economic development. Besides the equatorial deserts, there are many hot deserts situated in the tropical zone.
