Fresh water is the freely available (i.e. without the water bound in minerals and living beings) in which no or only very small amounts of salts ( salinity of less than 0.1 percent) are dissolved, regardless of its physical state . The proportion of fresh water in the earth's water balance is very low, at 2.6 to 3.5%, depending on the estimate; A significant proportion of the global freshwater resources is bound in ice in the form of glaciers and the ice of the polar caps or is available as fossil groundwater . The salt water of the oceans dominates.
The vast majority of global freshwater resources are bound in the ice of the glaciers in both polar regions and in some high mountains . In addition, fresh water is found, in particular, in the form of surface water from streams , rivers and lakes as well as in groundwater and aquifers formed in particular by seepage water from water-permeable rock .
Due to the global warming , the greenhouse gas emissions of the northern freshwater lakes could rise times 2.7 to 1.5 to as the vegetation cover in forests of northern latitudes and increases thereby dadeshalb more organic molecules get into the water, which microbes in the lake sediments be dismantled. During this degradation process, carbon dioxide and methane are released as by-products.
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