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Freshwater

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Freshwater

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ARTICLE TABLE OF CONTENTS
What is freshwater
Sources of freshwater
Distribution
Numerical definition
Freshwater as a resource
 
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What is freshwater

Freshwater is the water that one finds naturally in the surface of the Earth in ice layers, ice fields, glaciers, icebergs, wetlands, lagoons, lakes, rivers and creeks, and under the surface as underground water in aquifers and currents of underground water. Freshwater is generally characterized by having a low concentration of dissolved salts and a low level of dissolved solids. The term excludes specifically water of sea and salt water, though it includes waters rich in minerals, such as the sources of containing iron water. The term "freshwater" originated from the description of the water in contrast with saltwater.

Sources of freshwater

The source of almost the whole sweet water is the rainfall in the terrestrial atmosphere in the shape of fog, rain or snow. Freshwater that falls down as fog, rain or snow contains dissolved materials from the atmosphere as well as materials from the sea and the land on which the clouds move. In industrialized zones, the rain can be acid due to the dissolved oxides of sulphur and nitrogen that formed from the burning of fossil fuels of cars, factories, trains, planes and from the atmospheric emission of the industry. In some cases, this acid rain can contribute to the pollution of lakes and rivers.

In coastal areas, freshwater may contain significant concentrations of salt derived from the sea if the wind raises small drops of seawater in the rain-carrying clouds. This may result in increased concentrations of sodium, chloride, magnesium, and sulphate, as well as many other compounds in smaller concentrations.

In arid areas or areas with poor or dusty soils, rain-laden winds can carry sand and dust particles, which can be deposited in the form of precipitation elsewhere, resulting in a freshwater flow contaminated with measurable quantities of insoluble solids and soluble soil components. Significant amounts of iron can be transported in this way, such as the well-documented transfer of iron-rich precipitations falling in Brazil from sandstorms in the Sahara of North Africa.

 

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 Salinity
 Speciation
 Evaporation
Salt

Distribution

Water is a critical element for the survival of all living organisms in the Earth. Some organisms can use salty water, but many, including the great majority of plants and the majority of the mammals, must have access to sweet water to survive. Some terrestrial, such mammals as rodents of the desert, they seem to survive without drinking, but actually, they generate water across the metabolism of seeds of cereals and possess efficient mechanisms to preserve the water.

Of all the water in the Earth, the salty water - in the oceans, the seas, and the underground salty waters - represents 97 % of it. Only 2,5 to 2,75 % it is freshwater, including 1,75-2 % in the solid state in glaciers, ice and snow, 0,7-0,8 % in underground freshwater, and in the dampness of the soil, and less than 0,01 % of the total is superficial water found in lakes, marshes, and rivers.

Freshwater lakes contain 87 % of the total of superficial freshwater, including 29 % in the Great Lakes of Africa, 20 % in the Lake Baikal in Russia, 21 % in the Great Lakes of North America, and 14 % in other lakes. The marshes have most of the rest of the superficial waters, and the rivers only have a small quantity, especially the Amazon. The atmosphere only contains 0,04 % of water. In zones without superficial freshwater, and if this freshwater derives from the rainfalls can, due to his minor density, be superposed to the underground saline waters in lenses or layers. Most of the freshwater of the planet is frozen in the layers of ice. Important extensions, such as deserts, are characterized by the lack of freshwater.

Numerical definition

Freshwater can be defined as water with less than 500 parts per million (ppm) of dissolved salts.

Water levels of salinity based on dissolved salts
 Freshwater  Brackish water
Saltwater
 Brine
 < 0,05 % 0,05-3 %  3-5 %  > 5 %

 

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Freshwater as a resource

Freshwater is a natural and essential resource for the survival of all the ecosystems. The use of water by human beings for activities like the irrigation and industrial uses can have adverse effects on the ecosystems downstream. The chemical pollution of freshwater also can seriously damage the ecosystems. An important worry for the hydrological ecosystems is to assure a minimal flow, also for the preservation and restoration of water assignments, not consumptives. The pollution of the environment by the human activity, including the spillages of oil, also presents a problem for the resources of freshwater. The major spillage of oil that has happened in freshwater was caused by a Shell oil company tanker in Magdalena (Argentina), January 15th, 1999, contaminating water, flora, and fauna too.

The quantity of not contaminated freshwater is 0,003 % of the total of available water worldwide.

 

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