Surface water, groundwater
Although, being two separate entities, surface- and groundwater are part of an interrelated system, the global water cycle (hydrologic cycle). When surface water seeps through the soil it becomes groundwater and conversely, surface water sources can also be fed by groundwater.
Serving most of life's needs surface water makes up only around 1.2% of the total freshwater amount (being only 2.5% of all earth's water). Groundwater makes up around 30.1% of all freshwater. The following figure (left on the page) illustrates the composition in percentages of the total global water.
FIGURE The Earth's Water (http://ga.water.usgs.gov/edu/earthwherewater.html,accessed 2013-11-06)
Surface water
General Aspects
Surface water is any type of natural water on ground level that is, compared to groundwater, naturally open to atmosphere such as e.g. rivers, lakes, seas, wetlands, streams, and oceans.
|
Sources of surface water are:
|
Losses can be:
|
precipitation
|
evaporation (vaporization from the surface)
|
recruitment of groundwater
|
absorption by plants
|
|
seepage into the ground
|
|
abstraction by mankind for e.g. agriculture, industry, living
|
Global distribution of surface water
Throughout the globe surface water is naturally distributed in varying amounts since it is affected by precipitation, evaporation and runoff.
FIGUREThe World's Surface Water(http://www.grida.no/graphicslib/detail/worlds-surface-water-precipitation-evaporation-and-runoff_4701,accessed 2013-11-06)
Precipitation is any product of the condensation of atmospheric water vapour that falls under gravity. This can be drizzle, rain, sleet, snow, graupel and hail, as main forms.[1]
Evaporationis the vaporation of water from land or from the water surface.[2]
When the soil is infiltrated to full capacity and excess the water from rain, meltwater or other sources flows over the land, that is calledrunoff.[3]
