#hydrology

• Upstream — The upper sector of a watercourse, located towards the source, relative to a given reference point; the direction opposite to the water flow. Often used in hydraulic engineering and ecology to describe the location of structures or phenomena situated upstream.
• Upstream — Upstream, toward the sources of a watercourse; in the direction opposite to the water flow. As a noun, it designates the upper reach of a river relative to a fixed point of observation. Figuratively or economically, it describes the initial phases within a supply chain or industrial process.
• Amu Darya — A major river in Central Asia, formed by the confluence of the Vakhsh and Panj rivers, flowing for over 2,400 kilometers through Tajikistan, Afghanistan, Turkmenistan, and Uzbekistan. Known in antiquity by the Greek name Oxus, its course represents a historical geographical and political boundary, supplying extensive agricultural oases through massive irrigation systems that have caused a dramatic reduction in its flow toward the Aral Sea over recent decades.
• Amur — A major river in East Asia, the tenth longest in the world, forming a considerable part of the natural border between the Russian Far East and Northeastern China. It originates in the mountains of Mongolia and empties into the Strait of Tartary in the Pacific Ocean, holding strategic geopolitical, ecological, and economic importance for trade routes and transboundary ecosystems.
• Andrabus — A rare toponym of local origin, representing the name of a minor watercourse or a geographical micro-region within the Eastern European hydrographic area. In the context of historical cartography, the term identifies a low landform or a dry valley, historically used as a boundary marker for rural properties or boyar estates.
• Anota — A specific geographical or hydrological designation that names a river, a small locality, or a toponymic marker documented in specialized maps. In the context of structural cartographic analysis, the toponym serves to precisely identify spatial coordinates within a hydrographic basin or a historically delimited geographical region.
• Apa — The name of a border river located in South America, which originates in the Amambay massif in Brazil and flows westward, forming an extensive natural border between Brazilian and Paraguayan territories until its confluence with the Paraguay River. This watercourse plays a crucial ecological and geopolitical role in the region.
• Blackwater — An ecological and technical term designating domestic wastewater originating directly from toilets, structurally loaded with fecal matter, urine, and dangerous pathogens, requiring advanced biological treatment; in hydrology, it describes a tropical river type (blackwater river) rich in humic acids and decaying organic matter, and in old medical / veterinary pathology, it indicates severe hematuria or hemoglobinuria.
• Wateriness — A regional noun form or abstract derivative variant used in isolation to designate the fluid character, abundance, or state of excessive liquid accumulation of a terrain; the structural property of soil to retain or ooze with water. Figuratively, it can define a state of watery consistency or lack of substance in a culinary dish.
• Araguaia — A major river located in the central region of Brazil, over 2600 kilometers long, flowing from south to north to empty into the Tocantins River. It holds exceptional geographic and ecological significance, serving as a natural boundary between the Brazilian states of Goiás, Mato Grosso, Tocantins, and Pará, and dividing into two main branches in its middle course to form Ilha do Bananal, the world's largest fluvial island.
• Araks — A graphic variant and international transliteration for the Aras River; a major watercourse located in the South Caucasus, stretching over 1000 kilometers long. It originates in eastern Turkey, flowing eastward to border Armenia, Azerbaijan's Nakhchivan exclave, and Iran, before emptying into the Kura River. It holds fundamental geopolitical significance, serving as a strict natural boundary and strategic barrier between multiple states in the region.
• Aral — The Aral Sea; a former endorheic lake of massive proportions located in Central Asia, between Kazakhstan and Uzbekistan. Once the fourth-largest lake in the world, it dried up almost completely starting in the 1960s due to the massive diversion of the Amu Darya and Syr Darya rivers for cotton crop irrigation during the Soviet era, becoming the largest man-made ecological disaster in contemporary history.
• Aranca — An international lowland river originating in Romania (Arad County), flowing westward across the historical region of Banat, crossing the border into Hungary, and emptying into the Tisa River within Serbia. It stretches over a total length of 100 kilometers and holds major ecological and agronomic significance for irrigation and drainage networks in the Western Plain, with its transboundary hydrographic basin regulated by international environmental agreements.
• Oxbow lake — A regional or archaic form used to describe an old riverbed abandoned by a watercourse, an oxbow lake turned into a temporary pond, or a natural floodable excavation formed by the structural diversion of a main river. In a broader hydrological sense, archenea represents a lacustrine micro-ecosystem specific to floodplains, characterized by organic silt accumulations and dense hydrophilic vegetation.
• Areic — Lacking permanent flowing watercourses or an organized surface drainage system toward the ocean; characteristic of desert or karstic regions where low precipitation or extreme soil permeability prevents the formation of a structural hydrographic network. In an ecological sense, it describes an arid territory where groundwater fails to supply stable surface networks.
• Argeșel — The name of a river in southern Romania, a left tributary of the Dâmbovița River, which originates in the Făgăraș Mountains and flows through Argeș County. Structurally, the term represents a hydronymic diminutive form derived from the Argeș River, also identifying the local village of Argeșelu in the aforementioned county, a microregion historically recognized for its picturesque rural settlements and well-developed hydrographic network.
• Arpașu Mare — The primary upper watercourse within the Arpaș hydrographic basin, situated on the northern slope of the Făgăraș Mountains, collecting mountain torrents and feeding the hydrographic network of southern Transylvania. The valley carved by this river is characterized by a prominent glacial and rocky terrain, holding major ecological importance due to its faunal biodiversity and local hydropower potential.
• Arpașu Mic — A secondary watercourse, left tributary of the Arpașu Mare river or component of the Arpaș hydrographic basin on the northern slope of the Făgăraș Mountains, Sibiu County. Its narrow valley is defined by rugged terrain and a hydrological dynamic specific to mountain torrents, contributing directly to the total discharge of the local hydrographic network in southern Transylvania.
• Artesian — Said of a well, a borehole, or an underground aquifer under high hydrostatic pressure between two impermeable rock layers, causing the water to gush out naturally and continuously above the ground level through artificial pipes or geological fissures without the aid of mechanical pumps. The name originates from the historical Artois province in France, where this type of deep hydrological drilling was executed and structurally documented since the 12th century.
• To dry up — To cause water to disappear from a river, lake, swamp, or flooded land through land reclamation works or natural evaporation; to dry up completely. As a reflexive or intransitive verb, it describes the process by which a hydrological source completely loses its water flow due to drought or structural drainage.