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Freshwater
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Freshwater is a word that refers to bodies of water such as ponds, lakes, rivers and streams containing low concentrations of dissolved salts and other total dissolved solids. In other words, the term excludes seawater and brackish water. Freshwater can also be the output of desalinated seawater.
Freshwater is an important renewable resource, necessary for the survival of most terrestrial organisms, and is required by humans for drinking and agriculture, among many uses.
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Encyclopedia
Freshwater is a word that refers to bodies of water such as ponds, lakes, rivers and streams containing low concentrations of dissolved salts and other total dissolved solids. In other words, the term excludes seawater and brackish water. Freshwater can also be the output of desalinated seawater.
Freshwater is an important renewable resource, necessary for the survival of most terrestrial organisms, and is required by humans for drinking and agriculture, among many uses. The UN estimates that about 18 percent of the world's population lacks access to safe drinking water.
Numerical definition
Freshwater is defined as water with less than 0.5 parts per thousand dissolved salts. Freshwater bodies include lakes and ponds, rivers, some bodies of underground water and many kinds of man-made freshwater bodies, such as canals, ditches and reservoirs. The ultimate source of freshwater is the precipitation of atmosphere in the form of rain and snow.
Water distribution
Access to fresh water is a critical issue for the survival of many species, including humans, who must drink it in order to survive. Only three percent of the water on Earth is freshwater in nature, and about two-thirds of this is frozen in glaciers and polar ice caps. Most of the rest is underground and only 0.3 percent is surface water. Freshwater lakes, most notably Lake Baikal in Russia and the Great Lakes in North America, contain seven-eighths of this fresh surface water. Swamps have most of the balance with only a small amount in rivers, most notably the Amazon River. The atmosphere contains 0.04% water. In areas with no freshwater on the ground surface, freshwater derived from precipitation may, because of its lower density, overlie saline ground water in lenses or layers.
Aquatic organisms
Freshwater creates a hypotonic environment for aquatic organisms. This is problematic for some organisms, whose cell membranes will burst if excess water is not excreted. Some protists accomplish this using contractile vacuoles, while freshwater fish excrete excess water via the kidney. Although most aquatic organisms have a limited ability to regulate their osmotic balance and therefore can only live within a narrow range of salinity, diadromous fish have the ability to migrate between freshwater and saline water bodies. During these migrations they undergo changes to adapt to the surroundings of the changed salinities; these processes are hormonally controlled. The eel (Anguilla anguilla) uses the hormone prolactin, while in salmon (Salmo salar) the hormone cortisol plays a key role during this process.
Natural activity against human activity
Freshwater is a highly valuable natural resource that has a variety of uses in both human and natural activity. Freshwater is an important natural resource that allows certain ecosystems to survive. Flows of freshwater also bring soils and nutrients that are necessary in the growth and development of terrestrial plant life which forms the foundation of all food chains. However, the overuse of water by humans through activities such as irrigation and industrial applications have had a great negative impact on the water supply and the ecosystems that depend on it. Chemical contamination of freshwater can cause every organism in a certain body of water to die. The overuse of freshwater reduces the amount of available freshwater for the ecosystems that require it to survive. As a result, a large number of plant and animal species have become endangered or even extinct because their natural environment has been taken away from them. Usage of freshwater must be controlled before it causes even more damage in the environment and in human society.
Pollution from human activity, including oil spills, also presents a problem for freshwater resources. The largest oil spill that has ever occurred in freshwater was caused by a Shell tank ship in Magdalena, Argentina, on January 15, 1999, polluting the environment, drinkable water, plants and animals.
Agriculture- change of landscape
Changing landscape for the use of agriculture creates a great effect on flow of freshwater and surrounding. Reshaping a large scale of landscape in creating lands that are suitable for agriculture changed the flow and sustainability of freshwater which result in effecting the sustainability of the local ecosystem. Changes in landscape through the remove of trees and soils changed the local environments flow of freshwater and also effect the cycle of freshwater. As a result more freshwater are consumed and stored in soil which benefits agriculture. However, since agriculture was the human activity that consumes the most freshwater, freshwater would be used up completely which result in scarcity and destroy of local ecosystem. Similar to events happening in Australia where too much land and freshwater flow are restructured for the use of agriculture, which ends up causing 33% of lands area at risk of salinization and scarcity. Redesigning lands for the maximum use of agriculture will certainly bring a great damage to the environment and reduces the available freshwater supply since freshwater is a limiting natural resource.
Limiting resource
Freshwater is a renewable but limiting natural resource. As availability of freshwater in freshwater ecosystems decreases, nature restores it through the water cycle in the form of precipitation. Freshwater can only be renewed through the process of the water cycle, where water from seas, lakes, rivers, and dams evaporates, forms clouds, and returns to water sources as precipitation. However, if more freshwater is consumed through human activities than is restored by nature, the result is that the quantity of freshwater available in lakes, rivers, dams and underground waters is reduced which can cause serious damage to the surrounding environment.
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