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The Kalahari Desert is a large semi-arid sandy savanna in Southern Africa extending for 900,000 square kilometres (350,000 sq mi), covering much of Botswana, as well as parts of Namibia and South Africa.
A flood is an overflow of water that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrology and are of significant concern in agriculture, civil engineering and public health. Human changes to the environment often increase the intensity and frequency of flooding, for example land use changes such as deforestation and removal of wetlands, changes in waterway course or flood controls such as with levees, and larger environmental issues such as climate change and sea level rise. In particular climate change's increased rainfall and extreme weather events increases the severity of other causes for flooding, resulting in more intense floods and increased flood risk.
Lake Chad is a freshwater lake located at the junction of Nigeria, Niger, Chad and Cameroon in central and western Africa. It is also an important wetland ecosystem in West Africa. The catchment area of Lake Chad is 1 million square kilometers. It used to be a large lake with an area of 28,000 square kilometers in the 19th century. However, due to climate change and human water diversion, Lake Chad has been greatly reduced since the mid-1970s, and its area has fluctuated between 2,000 and 5,000 square kilometers.
Wetlands, or simply a wetland, is a distinct ecosystem that is flooded or saturated by water, either permanently or seasonally. Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The primary factor that distinguishes wetlands from terrestrial land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique anoxic hydric soils. Wetlands are considered among the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal species. Methods for assessing wetland functions, wetland ecological health, and general wetland condition have been developed for many regions of the world. These methods have contributed to wetland conservation partly by raising public awareness of the functions some wetlands provide. Constructed wetlands are designed and built to treat municipal and industrial wastewater as well as to divert stormwater runoff. Constructed wetlands may also play a role in water-sensitive urban design.
The Namib Desert 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.
Tonlé Sap is a lake in the northwest of Cambodia. It belongs to the Mekong River system. It is the largest freshwater lake in Southeast Asia and one of the most diverse and productive ecosystems in the world, designated as a Biosphere Reserve by UNESCO in 1997 due to its high biodiversity. Entering the 21st century, the lake and its surrounding ecosystems are under increasing pressure from deforestation, infrastructure development and climate change.
An endorheic basin is a drainage basin that normally retains water and allows no outflow to other, external bodies of water ; instead, the water drainage flows into permanent and seasonal lakes and swamps that equilibrate through evaporation. Endorheic basins also are called closed basins, terminal basins, and internal drainage systems.
The Kuiseb River is an ephemeral river in western-central Namibia. Its source is in the Khomas Highland west of Windhoek. From there it flows westwards through the Namib-Naukluft National Park and the Namib desert to Walvis Bay. Several settlements of the Topnaar people are on the banks of the lower Kuiseb, for instance Homeb, Sandfontein, Rooibank, and Utuseb. Inflows of the Kuiseb are Gomab, Ojab, Chausib, Gaub, Koam, Nausgomab and Goagos.
Wadi, alternatively wād, Maghrebi Arabic Oued, is the Arabic term traditionally referring to a river valley. In some instances, it may refer to a wet (ephemeral) riverbed that contains water only when heavy rain occurs.
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.
Lake Retba, also known as Lac Rose, lies north of the Cap Vert peninsula in Senegal, some 35 km (22 mi) north-east of the capital, Dakar, in northwest Africa. It is named for its pink waters caused by Dunaliella salina algae and is known for its high salt content, up to 40% in some areas. Its colour is usually particularly strong from late January to early March, during the dry season; however, flooding in September 2022 not only disrupted salt harvesting activities on the lake, but because it caused the lake to lose its colour, had a negative effect on tourism.
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.
Intermittent, temporary or seasonal rivers or streams cease to flow every year or at least twice every five years. Such rivers drain large arid and semi-arid areas, covering approximately a third of the earth's surface. The extent of temporary rivers is increasing, as many formerly perennial rivers are becoming temporary because of increasing water demand, particularly for irrigation. Despite inconsistent water flow, intermittent rivers are considered land-forming agents in arid regions, as they are agents of significant deposition and erosion during flood events. The combination of dry crusted soils and the highly erosive energy of the rain cause sediment resuspension and transport to the coastal areas. They are among the aquatic habitats most altered by human activities. During the summer even under no flow conditions the point sources are still active such as the wastewater effluents, resulting in nutrients and organic pollutants accumulating in the sediment. Sediment operates as a pollution inventory and pollutants are moved to the next basin with the first flush. Their vulnerability is intensified by the conflict between water use demand and aquatic ecosystem conservation. Advanced modelling tools have been developed to better describe intermittent flow dynamic changes such as the tempQsim model.
The Sahara pump theory is a hypothesis that explains how flora and fauna migrated between Eurasia and Africa via a land bridge in the Levant region. It posits that extended periods of abundant rainfall lasting many thousands of years in Africa are associated with a "wet-green Sahara" phase, during which larger lakes and more rivers existed. This caused changes in the flora and fauna found in the area. Migration along the river corridor was halted when, during a desert phase 1.8–0.8 million years ago (mya), the Nile ceased to flow completely and possibly flowed only temporarily in other periods due to the geologic uplift of the Nile River region.
The environmental impact of reservoirs comes under ever-increasing scrutiny as the global demand for water and energy increases and the number and size of reservoirs increases.
A lake is a naturally occurring, relatively large body of water localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from the ocean, although, like the much larger oceans, they form part of the Earth's water cycle by serving as large standing pools of storage water. Most lakes are freshwater and account for almost all the world's surface freshwater, but some are salt lakes with salinities even higher than that of seawater.
The African humid period is a climate period in Africa during the late Pleistocene and Holocene geologic epochs, when northern Africa was wetter than today. The covering of much of the Sahara desert by grasses, trees and lakes was caused by changes in the Earth's axial tilt; changes in vegetation and dust in the Sahara which strengthened the African monsoon; and increased greenhouse gases. During the preceding Last Glacial Maximum, the Sahara contained extensive dune fields and was mostly uninhabited. It was much larger than today, and its lakes and rivers such as Lake Victoria and the White Nile were either dry or at low levels. The humid period began about 14,600–14,500 years ago at the end of Heinrich event 1, simultaneously to the Bølling–Allerød warming. Rivers and lakes such as Lake Chad formed or expanded, glaciers grew on Mount Kilimanjaro and the Sahara retreated. Two major dry fluctuations occurred; during the Younger Dryas and the short 8.2 kiloyear event. The African humid period ended 6,000–5,000 years ago during the Piora Oscillation cold period. While some evidence points to an end 5,500 years ago, in the Sahel, Arabia and East Africa, the end of the period appears to have taken place in several steps, such as the 4.2-kiloyear event.
Climate change in the Middle East and North Africa (MENA) refers to changes in the climate of the MENA region and the subsequent response, adaption and mitigation strategies of countries in the region. In 2018, the MENA region emitted 3.2 billion tonnes of carbon dioxide and produced 8.7% of global greenhouse gas emissions (GHG) despite making up only 6% of the global population. These emissions are mostly from the energy sector, an integral component of many Middle Eastern and North African economies due to the extensive oil and natural gas reserves that are found within the region. The region of Middle East is one of the most vulnerable to climate change. The impacts include increase in drought conditions, aridity, heatwaves and sea level rise.
Lake Estancia was a lake formed in the Estancia Valley, central New Mexico, which left various coastal landforms in the valley. The lake was mostly fed by creek and groundwater from the Manzano Mountains, and fluctuated between freshwater stages and saltier stages. The lake had a diverse fauna, including cutthroat trout; they may have reached it during a possible past stage where it was overflowing.
The Mormyroidea are a superfamily of fresh water fishes endemic to Africa that, together with the families Hiodontidae, Osteoglossidae, Pantodontidae and Notopteridae, represents one of the main groups of living Osteoglossiformes. They stand out for their use of weak electric fields, which they use to orient themselves, reproduce, feed, and communicate.
References
- ↑ CEU. JRC. (2022). Drought in East Africa: August 2022 : GDO analytical report. LU: Publications Office. doi:10.2760/534446.
- ↑ Blanchet, Cécile L.; Osborne, Anne H.; Tjallingii, Rik; Ehrmann, Werner; Friedrich, Tobias; Timmermann, Axel; Brückmann, Warner; Frank, Martin (2021). "Drivers of river reactivation in North Africa during the last glacial cycle". Nature Geoscience. 14 (2): 97–103. doi:10.1038/s41561-020-00671-3. ISSN 1752-0894. S2CID 231746418.
- ↑ Murimi, S. K. (1994). "Falling water-levels in saline lakes of the central Rift Valley of Kenya: The case of Lake Elmenteita". International Journal of Salt Lake Research. 3 (1): 65–74. doi:10.1007/bf01990643. ISSN 1037-0544.
- ↑ Chidumayo, Emmanuel N.; Gumbo, Davison J. (2010). The dry forests and woodlands of Africa: managing for products and services. The earthscan forest library. London: Earthscan. ISBN 978-1-84971-131-9.
- ↑ Owen-Smith, Norman (2021-09-30). Only in Africa: The Ecology of Human Evolution (1 ed.). Cambridge University Press. doi:10.1017/9781108961646.006. ISBN 978-1-108-96164-6. S2CID 240545241.
- ↑ Rameshwaran, Ponnambalam; Bell, Victoria A.; Davies, Helen N.; Kay, Alison L. (2021). "How might climate change affect river flows across West Africa?". Climatic Change. 169 (3–4). doi: 10.1007/s10584-021-03256-0 . ISSN 0165-0009.
- ↑ Levêque, Christian; Paugy, Didier (2017), Paugy, Didier; Levêque, Christian; Otero, Olga (eds.), "Fish communities in river systems and associated biotopes", The inland water fishes of Africa, IRD Éditions, pp. 349–360, doi:10.4000/books.irdeditions.25241, ISBN 978-2-7099-2400-9 , retrieved 2023-07-03
- ↑ Stanzel, Philipp; Kling, Harald; Bauer, Hannes (2018-08-01). "Climate change impact on West African rivers under an ensemble of CORDEX climate projections". Climate Services. 11: 36–48. doi: 10.1016/j.cliser.2018.05.003 . ISSN 2405-8807.