question: How is an desert oasis possible if there's no natural underground water
comment: That place was not a desert, it was deserted. Granted it looks pretty arid but you can see in the before photo trees and grass and such so it must have adequate enough rainfall to support that. Once you start bringing back the trees this will hold even more of the water in that local environment as well. Oases are often centred around underground aquifers which will be the primary water source.
passages: Oases are made fertile when sources of freshwater, such as underground rivers or aquifers, irrigate the surface naturally or via man-made wells. 
  
  The presence of water on the surface or underground is necessary and the local or regional management of this essential resource is strategic, but not sufficient to create such areas: continuous human work and know-how (a technical and social culture) are essential to maintain such ecosystems..
   Until the 1980s, Saudi Arabia had lakes at Layla Aflaj and deep waterholes at 'Al-Kharj, fed by huge underground aquifers formed in prehistoric times and non-renewable. 'Al Kharj was a valuable source of drinking water in a barren terrain. In recent years, these aquifer have been drawn upon heavily, both for agricultural and domestic purposes, and no fresh water remain in the lakes or pits.
   People who live in an oasis must manage land and water use carefully; fields must be irrigated to grow plants like apricots, dates, figs, and olives. The most important plant in an oasis is the date palm, which forms the upper layer. These palm trees provide shade for smaller trees like peach trees, which form the middle layer. By growing plants in different layers, the farmers make best use of the soil and water. Many vegetables are also grown and some cereals, such as barley, millet, and wheat, are grown where there is more moisture.
   In North American history, oases have been less prominent since the desert regions are smaller, but in the USA they have allowed colonisation of the western desert regions around the Rockies. Las Vegas is an example of such a settlement.
  
  Section::::Growing plants.
   Section::::Origin and development.:Dune field.
  
  If the coast has dune fields, then flooding creates many smaller pools between the crests of the dunes. In some parts of the world, these lakes can also form in inland deserts, filled by rain or a rising water table from underground aquifers.
  
  For example, large parts of the Empty Quarter in Saudi Arabia and the southern UAE consist of patterns of high drifting barchan dunes alternating with sabkha salt flats. In some places, the sabkha connect to form long accessible corridors into the desert.
   Over 300 species of plants, 10 species of carnivores and numerous species of permanent and migratory birds have been recorded until this date. Some of the remote mountain and valley areas are difficult to reach, and thus offer safe havens for rare species of cats, goats and other mountain animals.
   When rain falls in deserts, as it occasionally does, it is often with great violence. The desert surface is evidence of this with dry stream channels known as arroyos or wadis meandering across its surface. These can experience flash floods, becoming raging torrents with surprising rapidity after a storm that may be many kilometers away. Most deserts are in basins with no drainage to the sea but some are crossed by exotic rivers sourced in mountain ranges or other high rainfall areas beyond their borders. The River Nile, the Colorado River and the Yellow River do this, losing much of their water through evaporation as they pass through the desert and raising groundwater levels nearby. There may also be underground sources of water in deserts in the form of springs, aquifers, underground rivers or lakes. Where these lie close to the surface, wells can be dug and oases may form where plant and animal life can flourish. The Nubian Sandstone Aquifer System under the Sahara Desert is the largest known accumulation of fossil water. The Great Man-Made River is a scheme launched by Libya's Colonel Gadaffi to tap this aquifer and supply water to coastal cities. Kharga Oasis in Egypt is long and is the largest oasis in the Libyan Desert. A lake occupied this depression in ancient times and thick deposits of sandy-clay resulted. Wells are dug to extract water from the porous sandstone that lies underneath. Seepages may occur in the walls of canyons and pools may survive in deep shade near the dried up watercourse below.
   In the aforementioned chapters and in "Rocks", Abbey also describes at length the geology he encounters in Arches National Monument, particularly the iconic formations of Delicate Arch and Double Arch. In "Water", Abbey discusses how the ecosystem adapts to the arid conditions of the Southwest, and how the springs, creeks and other stores of water in their own ways support some of the diverse but fragile plant and animal life. Some of the oddities of water in the desert, such as flash floods and quicksand, are also explored.
   Farming in karst areas must take into account the lack of surface water. The soils may be fertile enough, and rainfall may be adequate, but rainwater quickly moves through the crevices into the ground, sometimes leaving the surface soil parched between rains.
   A buried river bed "not only serves in certain cases to carry into the heart of the desert the waters of distant rains which have fallen outside the desert domain, but in it the waters of the local storms are concentrated and carried swiftly to the alluvial basins where they are imbibed by the lighter earth and form lasting reserves within its depths. The result is that what vegetation survives is localized along the wadi beds or in their basins; in fact the words wadi and pasturage are interchangeable in the language of the nomads, who habitually reside in such places."
   The water is freshest, cleanest, and coolest in the upper reaches and more prosperous people live at the outlet or immediately upstream of the outlet. When the qanat is still below ground, the water is drawn to the surface via water wells or animal driven Persian wells. Private subterranean reservoirs could supply houses and buildings for domestic use and garden irrigation as well. Further, air flow from the qanat is used to cool an underground summer room (shabestan) found in many older houses and buildings.
   The second factor restricting the development of Serene Oasis is the limitation of land utilization. Due to the fact that the urban land is limited, it is necessary to make an efficient disposition of land. Although the land in Serene Oasis is already being highly utilized, it is not yet enough for further developing their activities in order to expand the range of social services.
   I am almost prepared to believe that this sweet virginal primitive land would be grateful for my departure and the absence of the tourist, will breath metaphorically a collective sigh of relief - like a whisper of wind – when we are all and finally gone and the place and its creations can return to their ancient procedures unobserved and undisturbed by the busy, anxious, brooding consciousness of man.
   David Mattingly reports foggara extending for hundreds of miles in the Garamantes area near Germa in Libya: "The channels were generally very narrow – less than 2 feet wide and 5 high – but some were several miles long, and in total some 600 foggara extended for hundreds of miles underground. The channels were dug out and maintained using a series of regularly spaced vertical shafts, one every 30 feet or so, 100,000 in total, averaging 30 feet in depth, but sometimes reaching 130."
  
  Section::::Qanats by country.:Africa.:Tunisia.
   BULLET::::- Al-Ahsa Oasis : The Al-Ahsa Oasis is a serial property comprising gardens, canals, springs, wells and a drainage lake, as well as historical buildings, urban fabric and archaeological sites.
   Antarctic oases and dry valleys develop in areas with particular regional weather patterns and geography. These areas have very low humidity and precipitation. Although these areas are very cold, sufficient solar energy is absorbed by the ground to melt what little snow does fall, or else it is scoured or sublimated by katabatic winds leaving the underlying rock exposed.
  
  Despite usually extreme aridity, some plants, in the form of bryophytes and lichens, can survive in Antarctic oases.
  
  Section::::Geography.
  
  The larger oases are:
  
  BULLET::::- McMurdo Dry Valleys, about , Victoria Land
  
  BULLET::::- Cape Hallett, northern Victoria Land
   Section::::Unconfirmed systems.
  
  There have been numerous reports of the testing of unconfined geothermal systems pressure-stimulated in crystalline basement rock: for instance at the Rosemanowes quarry in Cornwall, England; at the Hijiori and Ogachi calderas in Japan; at the faulted Soultz-sous-Forêts “HDR” system in France; and in the Cooper Basin, Australia. However, all these “engineered” geothermal systems, while developed under programs directed toward the investigation of HDR technologies, have proven to be open—as evidenced by the high water losses observed during pressurized circulation. In essence, they are all EGS or hydrothermal systems, not true HDR reservoirs.
  
  Section::::Enhanced geothermal systems.
   In summary, an oasis palm grove is a highly anthropized and irrigated area that supports a traditionally intensive and polyculture-based agriculture. The oasis is integrated into its desert environment through an often close association with nomadic transhumant livestock farming (very often pastoral and sedentary populations are clearly distinguished). However, the oasis is emancipated from the desert by a very particular social and ecosystem structure. Responding to environmental constraints, it is an integrated agriculture that is conducted with the superposition (in its typical form) of two or three strata creating what is called the "oasis effect " :
   The slopes of the mountainous land are very sparsely vegetated, with a steppe-type vegetation on plateaus. Groundwater seepage does occur in places along the Dead Sea shore, for example at the hot springs of Zara, which support a luxuriant thicket of Acacia, Tamarix, Phoenix and Nerium, and a small marsh. The less severe slopes of the reserve are used by pastoralists for the grazing of sheep and goats.
  
  The hot springs of Hammamat Ma'in lie close to the borders of the reserve are heavily used for tourism and recreation.
   Rain showers provide subterranean water to sustain natural oases, such as the Tuat. Substrata of impermeable rock and stone can trap water and retain it in pockets, or on long faulting subsurface ridges or volcanic dikes water can collect and percolate to the surface. Any incidence of water is then used by migrating birds, which also pass seeds with their droppings which will grow at the water's edge forming an oasis. It can also be used to plant crops.
  
  Section::::Historical significance.
   The oasis of Turpan, in the deserts of Xinjiang in northwestern China, uses water provided by qanat (locally called "karez"). The number of karez systems in the area is slightly below 1,000, and the total length of the canals is about 5,000 kilometers.
   The 60 to 80 meter thick Quaternary Gezira, Atshan and Gash Formations are unconfined and unconsolidated aquifers, composed of alluvial sand, silt, clay and gravel with high quality water. The Gezira and Atshan aquifers are recharged by water leakage from the Blue and White Nile, while the Gezira is recharged from the Gezira River. The Um Ruwaba Formation, by contrast is also unconsolidated and sometimes several hundred meters thick, but recharges very slowly from rainwater, limiting its use to domestic production and livestock watering.
   Once the (fresh or sea)water has been attained in centralized systems it must be distributed. This can be done using dug canals or in some instances aqueducts (which are both the least attractive option since they allow much water to be evaporated), troughs (as used in the Keita Project), earthenware piping (semi-open or closed) or even underground systems i.e. qanāt.
   Section::::Topography.
   Geothermal has minimal land and freshwater requirements. Geothermal stations use 404 square meters per GW·h versus 3,632 and 1,335 square meters for coal facilities and wind farms respectively. They use 20 litres of freshwater per MW·h versus over 1000 litres per MW·h for nuclear, coal, or oil.
  
  Geothermal power stations can also disrupt the natural cycles of geysers. For example, the Beowawe, Nevada geysers, which were uncapped geothermal wells, stopped erupting due to the development of the dual-flash station.
  
  Section::::Economics.
  
presuppositions: Natural underground water is the sole source of water in a desert oasis. Oases do not have any natural underground water.
corrections: Rain and underground aquifers can be sufficient water sources in a desert oasis. Oases are often centered around underground aquifers which provides a water source.
raw_presuppositions: Natural underground water is the sole source of water in a desert oasis. Oases do not have any natural underground water.
raw_corrections: Rain and underground aquifers can be sufficient water sources in a desert oasis. Oases are often centered around underground aquifers which provides a water source.