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The management of water resources, protection against floods and hydropower are not new concepts. Regardless, river engineering has changed in the past century because of environmental concerns. The available amount and type of data about rivers has increased which provides more useful information about the behaviour of rivers and their ecosystems.
Rain falling over a drainage basin in Scotland.Understanding the cycling of water into, through, and out of catchments is a key element of hydrology. Hydrology (from Ancient Greek ὕδωρ (húdōr) 'water' and -λογία () 'study of') is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and ...
Climate change and greater demands on water resources require a more knowledgeable disposition of arguably one of our most vital resources. Because water in its occurrence varies spatially and temporally throughout the hydrologic cycle, its study using GIS is especially practical. Whereas previous GIS systems were mostly static in their ...
Long-lived river systems can produce a series of terrace surfaces over the course of their geologic lifetime. When rivers flood, sediment deposits in sheets across the floodplain and build up over time. Later, during a time of river erosion, this sediment is cut into, or incised, by the river and flushed downstream. The previous floodplain is ...
Most water in Earth's atmosphere and crust comes from saline seawater, while fresh water accounts for nearly 1% of the total. The vast bulk of the water on Earth is saline or salt water, with an average salinity of 35‰ (or 3.5%, roughly equivalent to 34 grams of salts in 1 kg of seawater), though this varies slightly according to the amount of runoff received from surrounding land.
As water flows downstream, streams and rivers most often gain water volume, so at base flow (i.e., no storm input), smaller headwater streams have very low discharge, while larger rivers have much higher discharge. The "flow regime" of a river or stream includes the general patterns of discharge over annual or decadal time scales, and may ...
Water first enters rivers through precipitation, whether from rainfall, the runoff of water down a slope, the melting of glaciers or snow, or seepage from aquifers beneath the surface of the Earth. Rivers flow in channeled watercourses and merge in confluences to form drainage basins , areas where surface water eventually flows to a common outlet.
Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply [3] [4] and 90% of habitable space on Earth. [5] Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. [6]