Freshwater (or fresh water ) is any water that occurs naturally except sea water and brackish water. Fresh water includes water in ice sheets, ice caps, glaciers, icebergs, swamps, ponds, lakes, rivers, rivers, and even underground water called ground water. Fresh water is generally characterized by low concentrations of dissolved salt and other total dissolved solids. Although this term specifically excludes seawater and brackish water, it includes mineral-rich water such as chalybeate springs.
Fresh water is not the same as drinking water (or drinking water). Most of the freshwater on earth (on the surface and ground water) is not suitable for unhealthy drinking. Fresh water can easily become polluted by human activity or due to a naturally occurring process, such as erosion.
Water is essential for the survival of all living organisms. Some organisms can thrive in saltwater, but most high-level plants and most mammals need fresh water to live.
The term "sweet water" is used to describe fresh water different from salt water.
Video Fresh water
Definition
Numerical definitions
Fresh water can be defined as water with less than 500 parts per million (ppm) of dissolved salt.
Other sources provide higher upper salinity limits for fresh water, eg. 1000 ppm or 3000 ppm.
System
The freshwater habitat is divided into a lentik system, which is groundwater including ponds, lakes, swamps and mires; lotic systems, or running water; and ground water that flows in rocks and aquifers. There is, in addition, a bridging zone between the groundwater system and the lotic system, which is the hyporheic zone, which underlies many of the larger rivers and can contain more water than is seen in open channels. It may also be directly related to underground underlying water.
The majority of freshwater on Earth is in the ice.
Maps Fresh water
Source
The source of almost all freshwater is the deposition of the atmosphere, in the form of fog, rain and snow. Freshwater falls like fog, rain or snow containing dissolved matter from the atmosphere and material from the sea and the soil where rain brings clouds have traveled. In industrial areas, rain is usually acidic because of sulfur oxides and dissolved nitrogen formed from burning fossil fuels in cars, factories, trains and airplanes and from industrial atmospheric emissions. In some cases this acid rain produces lake and river pollution.
In freshwater coastal areas may contain significant salt concentrations coming from the ocean if windy conditions have raised sea water droplets into clouds that carry rain. This can increase the concentration of sodium, chloride, magnesium and sulfate as well as many other compounds in smaller concentrations.
In desert areas, or areas with poor or dusty soil, blowing winds can pick up sand and dust and these can be stored elsewhere in deposition and cause freshwater flow to be contaminated measurably both by insoluble solids but also by soluble components of the lands. Significant amounts of iron can be transported in this way including the well-documented, iron-rich rainfall transfer that falls in Brazil from sandstorms in the Sahara in North Africa.
Water distribution
Of all the water on Earth, saltwater in the ocean, sea, and saltwater water makes up about 97% of it. Only 2.5-2.75% are fresh water, including 1.75-2% frozen in glaciers, ice and snow, 0.5-0.75% as fresh groundwater and soil moisture, and less than 0.01 % of it as surface water in lakes, swamps and rivers. The freshwater lake contains about 87% of this fresh surface water, including 29% in the Great Lakes of Africa, 22% in Lake Baikal in Russia, 21% in the Great Lakes of North America, and 14% in other lakes. Swamps have most of the balance with only a small amount in the river, especially the Amazon River. The atmosphere contains 0.04% water. In areas with no fresh water at ground level, fresh water comes from possible rainfall, due to its lower density, overthrowing salty groundwater in the lens or lining. Most of the world's fresh water froze on the ice sheet. Many regions suffer from a lack of freshwater distribution, such as deserts.
Aquatic organism
Water is a critical issue for the survival of all living organisms. Some can use saltwater but many organisms include most of the higher plants and most mammals should have access to fresh water for life. Some terrestrial mammals, especially desert rodents seem to survive without drinking but they produce water through cereal seed metabolism and they also have a mechanism to conserve water to a maximum extent.
Fresh water creates a hypotonic environment for aquatic organisms. This is problematic for some organisms with translucent skin or with gill membranes, whose cell membranes can explode if excess water is not excreted. Some protists achieve this using contractile vacuoles, while freshwater fish secrete excess water through the kidneys. Although most aquatic organisms have limited ability to regulate their osmotic balance and therefore can live only within a narrow range of salinity, diadromous fish have the ability to migrate between freshwater and saltwater bodies. During this migration they experience changes to adapt to changing salinity environments; these processes are controlled hormonally. Eel (Anguilla anguilla) uses the hormone prolactin, while in salmon ( Salmo salar ) the hormone cortisol plays a key role during this process.
Many seabirds have special glands at the base of the bill where excess salt is excreted. Similarly marine iguanas in the GalĂƒppagos Islands emit excess salt through the nose glands and they secrete very salty excretions.
Freshwater molluscs include freshwater snails and freshwater bivalves. Freshwater crustaceans include freshwater crabs, and more.
Problem
Limited resources
Fresh water is a renewable and varied natural resource, but limited. Fresh water can only be replenished through a process of water cycle, where water from the sea, lakes, forests, soil, rivers, and reservoirs evaporates, forms clouds, and returns as a precipitation. However locally, if more fresh water is consumed through human activities than is naturally restored, this can lead to reduced availability of fresh water from surface and underground sources and can cause serious damage to surrounding and related environments.
Clean and uncontaminated water equal to 0.003% of the total water available globally.
Increasing world population and increasing water use per capita puts an increase in the availability of limited resources from clean water. The World Bank adds that responses by freshwater ecosystems to climate change can be described in three interrelated components: water quality, water quantity or volume, and water time. Changes in one often cause a shift in the other as well. Water pollution and subsequent eutrophication also reduce freshwater availability.
Many regions of the world are already experiencing stress on the availability of water (or water scarcity). Because of the accelerating rate of population growth and the increase in the amount of water used by one person, it is expected that this situation will continue to deteriorate. Future water shortages will harm the human population as it will affect everything from sanitation, overall health, and grain production.
Minimum flow stream
An important concern for hydrological ecosystems is securing minimum flow, especially preserving and restoring incoming water allocations. Fresh water is an important natural resource for the survival of all ecosystems. The use of water by humans for activities such as irrigation and industrial applications can adversely affect the downstream ecosystem.
Withdrawal of fresh water is the amount of water discharged from available sources for use in any purpose, excluding evaporation losses. The water being withdrawn is not fully consumed and some can be returned for further use downstream.
Water pollution
Pollution from human activities, including oil spills and also presents problems for freshwater resources. The largest oil spill ever occurring in fresh water was caused by Royal Dutch Shell tanker ship in Magdalena, Argentina, on January 15, 1999, polluting the environment, drinking water, plants and animals. Freshwater chemical contamination can also seriously damage the ecosystem.
Human use
Agriculture
Changing the landscape for agricultural use has a major influence on freshwater flow. The landscape change by the removal of trees and soil changes the flow of fresh water in the local environment and also affects the freshwater cycle. As a result, more fresh water is stored on land that benefits agriculture. However, since agriculture is a human activity that consumes the freshest water, it can put heavy pressure on local fresh water resources that cause damage to local ecosystems.
In Australia, over-abstraction of fresh water for intensive irrigation activities has caused 33% of the land area to be at risk of salination. In relation to agriculture, the World Bank is targeting food production and water management as an increasingly global issue that will encourage debate.
Example
With one in eight people in the world who do not have access to safe water, it is important to use these resources in a wise manner. Utilizing the best possible water locally might provide the best solution. Local people need to plan the use of fresh water and should be made aware of how certain plants and animals use water.
As a guide, the following table provides some indicators.
Table 1 Recommendations of basic water needs for human needs (per person)
Table 2. Water requirements of different classes of livestock
Table 3 Estimated value of seasonal crop water requirements
See also
References
External links
- The World Bank's work and publications on water resources
- US. Geological Survey
- Fresh Water Geography
Source of the article : Wikipedia
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