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The deuterium to hydrogen ratio for ocean water on Earth is known very precisely to be (1.5576 ± 0.0005) × 10 −4. [36] This value represents a mixture of all of the sources that contributed to Earth's reservoirs, and is used to identify the source or sources of Earth's water.
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.
Water is an inorganic compound with the chemical formula H 2 O.It is a transparent, tasteless, odorless, [c] and nearly colorless chemical substance.It is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent [20]).
Water is the most abundant substance on Earth's surface and also the third most abundant molecule in the universe, after H 2 and CO. [23] 0.23 ppm of the earth's mass is water and 97.39% of the global water volume of 1.38 × 10 9 km 3 is found in the oceans. [84]
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 ...
Water resources are natural resources of water that are potentially useful for humans, for example as a source of drinking water supply or irrigation water. These resources can be either freshwater from natural sources, or water produced artificially from other sources, such as from reclaimed water or desalinated water (). 97% of the water on Earth is salt water and only three percent is fresh ...
Chemical hydrology – the study of the chemical characteristics of water; Ecohydrology – the study of interactions between organisms and the hydrologic cycle; Hydrogeology – the study of the presence and movement of water in aquifers; Hydroinformatics – the adaptation of information technology to hydrology and water resources applications
Water distribution on Earth – Overview of the distribution of water on planet Earth; Water cycle – Biogeochemical cycle for movement of water on Earth; Groundwater – Water located beneath the ground surface; Body of water – Any significant accumulation of water, generally on a planet's surface Salt water – Water that contains a high ...