Global Water Budget

1245 Words5 Pages
The hydrosphere comprises all water on earth, in all its forms and locations. Water covers 80% of our planet, and of it, fresh water accounts for just 2.5%. Furthermore, only about one percent is available for people to use. The majority, 97%, is salt water in the oceans; the rest is locked in the ice caps or groundwater distributed all over the world. The earth has had the same amount of water for millions of years. This is made possible by the water (hydrological) cycle which circulates water, constantly moving and changing from one state to another (solid, liquid, or vapour/gas). The many interactions of the atmosphere, lithosphere, and biosphere are responsible for this transition of forms, although the core power of the first stage of movement is from the energy of the sun. The sun provides energy to first evaporate liquid to vapour, which starts the other processed involved in this cycle: precipitation, condensation, transpiration, runoff and percolation/infiltration. The Earth's system of cycling water is viewed as the continual displacement of water taken from the ocean, transported through the atmosphere, deposited over land, and ultimately fed back to the ocean. However, many processes and pathways are responsible for this global transit and cycling and the distribution in different areas. Therefore, to monitor the global water cycle in the context of all of these key interactions with the global environment requires a comprehensive representation of the budgets and cycling of all phases of water storage; the global water budget. The lithosphere is the solid rocky crust of the earth that interacts with all the other spheres. Water that is distributed onto land in the form of precipitation is very common and leads to many processes and uses. As the water runs down on a gradient surface of the earth, it leads to runoff. When snow melts into water
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