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| | + | = Surface water, groundwater<br/> = |
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| | + | ---- |
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| | + | <font size="2" style="font-size: 11pt"><span style="font-weight: normal">Although, being two separate entities, surface- and groundwater are part of an interrelated system, the global water cycle (hydrologic cycle</span></font><font size="2" style="font-size: 11pt"><span style="font-weight: normal">). When surface water seeps through the soil it becomes groundwater and conversely, surface water sources can also be fed by groundwater.</span></font><br/> |
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| | + | <font size="2" style="font-size: 11pt">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. </font>The following figure (left on the page) illustrates the composition in percentages of the total global water.<br/> |
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| | + | '''<span style="color:#008000">FIGURE</span> '''<span style="display: none" data-cke-bookmark="1"></span><u>The Earth's Water</u> <span style="color:#008000"></span><span style="color:#008000"><span style="display: none" data-cke-bookmark="1"></span>''([http://ga.water.usgs.gov/edu/earthwherewater.html http://ga.water.usgs.gov/edu/earthwherewater.html]''<font size="2">,</font></span>'''<font size="2" style="font-size: 11pt"><span style="font-weight: normal">accessed 2013-11-06)</span></font>'''<br/> |
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| | + | == '''Surface water''' == |
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| | + | ---- |
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| | + | === General Aspects === |
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| | + | <font size="2" style="font-size: 11pt">Surface water is any type of natural water on ground level that is, compared to groundwater, naturally <span style="font-weight: normal">open to atmosphere</span> such as e.g. rivers, lakes, seas, wetlands, streams, and oceans.</font> |
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| | + | {| cellspacing="1" cellpadding="5" border="1" style="width: 540px" |
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| | + | <font size="2" style="font-size: 11pt">'''Sources''' of surface water are:</font><br/> |
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| | + | <font size="2" style="font-size: 11pt">'''Losses''' can be:</font><br/> |
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| | + | | style="width: 225px" | <font size="2" style="font-size: 11pt">precipitation</font><br/> |
| | + | | style="width: 286px" | <font size="2" style="font-size: 11pt">evaporation (vaporization from the surface)</font><br/> |
| | + | |- |
| | + | | style="width: 225px" | <font size="2" style="font-size: 11pt">recruitment of groundwater</font><br/> |
| | + | | style="width: 286px" | <font size="2" style="font-size: 11pt">absorption by plants</font><br/> |
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| | + | | style="width: 225px" | <br/> |
| | + | | style="width: 286px" | <font size="2" style="font-size: 11pt">seepage into the ground</font><br/> |
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| | + | | style="width: 225px" | <br/> |
| | + | | style="width: 286px" | <font size="2" style="font-size: 11pt">abstraction by mankind for e.g. agriculture, industry, living</font><br/> |
| | + | |} |
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| | + | === Global distribution of surface water === |
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| | + | <font size="2" style="font-size: 11pt">Throughout the globe surface water is naturally <span style="font-weight: normal">distributed</span> in varying amounts since it is affected by precipitation, evaporation and runoff.</font><br/> |
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| | + | <span style="color:#008000">'''<span style="color:#008000">FIGURE</span>'''</span><font size="2" style="font-size: 11pt"><span style="font-weight: normal"></span><u><span style="font-weight: normal">The World's Surface Water</span></u><span style="font-weight: normal"></span><span style="font-weight: normal"></span><span style="font-weight: normal"></span><span style="font-weight: normal"></span><span style="font-weight: normal"></span></font>''<font size="2" style="font-size: 11pt"><span style="font-weight: normal"></span></font>''<span style="color:#008000">''<font size="2" style="font-size: 11pt"><span style="font-weight: normal">(<span style="color:#0000ff">[http://www.grida.no/graphicslib/detail/worlds-surface-water-precipitation-evaporation-and-runoff_4701 http://www.grida.no/graphicslib/detail/worlds-surface-water-precipitation-evaporation-and-runoff_4701]</span></span></font>''</span>''<font size="2" style="font-size: 11pt"><span style="font-weight: normal">,</span></font>'''''<font size="2" style="font-size: 11pt">''<span style="font-weight: normal">accessed 2013-11-06</span>''</font>'''<font size="2" style="font-size: 11pt"><span style="font-weight: normal">)</span></font><br/> |
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| | + | <p style="text-align: right"><span style="color:#008000">''<font color="#008000"><font size="2" style="font-size: 11pt">'''Precipitation'''</font></font> '''<font color="#008000"><font size="2" style="font-size: 11pt"><span style="font-weight: normal">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.<ref>"Precipitation". Glossary of Meteorology. American Meteorological Society. 2009. Retrieved 2009-01-02</ref></span></font></font>'''''</span><br/></p><p style="text-align: right"><span style="color:#008000">''<font color="#008000"><font size="2" style="font-size: 11pt">'''Evaporation'''</font></font>'''<font color="#008000"><font size="2" style="font-size: 11pt"><span style="font-weight: normal">is the vaporation of water from land or from the water surface.<ref>H. Häckel: Meteorologie. UTB 1338. Ulmer Verlag, Stuttgart 1999 (4. Aufl.)</ref></span></font></font>'''''</span><br/></p><p style="text-align: right"><span style="color:#008000">''<font color="#008000"><font size="2" style="font-size: 11pt"><span style="font-weight: normal">When the soil is infiltrated to full capacity and excess the water from rain, meltwater or other sources flows over the land, that is called</span></font><font size="2" style="font-size: 11pt">'''runoff'''.</font></font>''</span><ref>Keith Beven, Robert E. Horton's perceptual model of infiltration processes, Hydrological Processes, Wiley Intersciences DOI 10:1002 hyp 5740 (2004)</ref><br/></p><div dir="LTR" id="sdfootnote2"> |
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| | + | <font size="2" style="font-size: 11pt">The figure shows the uneven distribution world's surface water by illustrating the amount of precipitation in cubic meter for the major regions of the world and the percentage of that amount which becomes runoff or evaporates. Asia receives the highest precipitation and loses most of that water by evaporation although compared to the other regions, to a low rate.</font><br/> |
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| | + | <font size="2" style="font-size: 11pt">Asia, South America and Africa reveive the greatest amounts of precipitation. The evaporation rate is highest in Africa due to climatic conditions. In all regions the evaporation rate exceeds the amount of water carried away by runoff. In Asia and North America almost half of all surface water becomes runoff or evaporates.</font><br/> |
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| | + | <font size="2" style="font-size: 11pt">Europe, Australia and Oceania receive only about a quarter of the total surface water of Asia and in both regions around one third of all precipitation evaporates whereas the remaining third becomes runoff.</font><br/> |
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| | + | === Contamination<br/> === |
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| | + | Based on their origin sources of surface water pollution are generally grouped into two categories – point sources and non-point sources (NPS). If contaminants enter a waterway from a single, indentifiable source (e.g. pipe, ditch, discharge from a sewage treatment plant) it is called a '''point source'''. It is defined in section 502(14) of the U.S. Clean Water Act.<br/> |
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| | + | '''NPS '''is any source of water pollution that does not meet the legal definition of "point source" in section 502(14) of the Clean Water Act. Examples for NPS are:<br/> |
| | + | *Excess fertilizers, herbicides and insecticides from agricultural lands and residential areas |
| | + | *Oil, grease and toxic chemicals from urban runoff and energy production<br/> |
| | + | *Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks |
| | + | *Salt from irrigation practices and acid drainage from abandoned mines |
| | + | *Bacteria and nutrients from livestock, pet wastes and faulty septic systems |
| | + | *Atmospheric deposition and hydromodification<ref>http://water.epa.gov/polwaste/nps/whatis.cfm [accessed 1.12.2013]</ref><br/> |
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| | + | Contaminated water poses a high risk also to health. Common water and sanitation-related diseases are diarrhoea, arsenicosis, cholera, flourosis, guinea worm disease, HIV/AIDS, intestinal worms, malaria, schisosomiasis, trachoma or typhoid.<ref>UNICEF (2003) Water, Sanitation and Hygiene. URL: http://www.unicef.org/wash/index_wes_related.html, accessed 2013-12-12 </ref><br/> |
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| | + | == '''Groundwater'''<br/> == |
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| | + | === General Aspects<br/> === |
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| | + | Groundwater represents one of the most important resources for drinking water for human consumption. Worldwide 2.5 billion people are solely dependend on groundwater to satisfy their daily needs for water.<ref>UNESCO (2012) News 31.05.2012 URL: http://www.unesco.org/new/en/natural-sciences/environment/water/single-view-fresh-water/news/worlds_groundwater_resources_are_suffering_from_poor_governance_experts_say/#.UqjsvyeotF4 [accessed 11.12.2013]</ref> With withdrawl rates of currently 982 km3/year (estimated) groundwater ist the world's most extracted raw material.<ref>Margat, J., and J. van der Gun (2013) Groundwater around the World, CRC Press/Balkema</ref> Groundwater can act as a natural water storage and can buffer against shortages of surface water, as in during times of drought. <ref>Anrew J. Elmore, Sara J. Manning, John F. Mustard, Joseph M. Craine (2006) Decline in alkali meadow vegetation cover in California: the effects of groundwater extraction and drought. Journal of Applied Ecology 43 (4), 770–779.</ref> About 38 % of the worldwide irrigated lands are irrigated with groundwater.<ref>Siebert, S., et al. (2010) Groundwater use for irrigation. Hydrology and Earth Systems Science, 14, 1863–1880. www.hydrol-earth-syst-sci.net/14/1863/2010/doi:10.5194/hess-14-1863-2010</ref><br/> |
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| | + | === Origin<br/> === |
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| | + | If surface water seeps into the soil it becomes soil moisture or groundwater. In the graphic groundwater flow, two types of aquifers (confined and unconfined) and three types of wells (artesian; flowing artesian and a water table well in an unconfined aquifer) are shown. The figure illustrates how groundwater is recharged and how it circulates through the aquifers.<br/><span style="color:#008000"><span style="color:#008000">'''FIGURE'''</span> </span><u>Groundwater: aquifers, wells and circulation</u><span style="color:#008000">(<span style="color:#0000ff">''[http://www.grida.no/graphicslib/detail/groundwater-aquifers-wells-and-circulation_8b39# http://www.grida.no/graphicslib/detail/groundwater-aquifers-wells-and-circulation_8b39#]''</span></span>, accessed 2013-12-12)<span style="color:#008000"></span><br/><br/> |
| | + | <p style="text-align: right"><span style="color:#008000"><br/><font color="#009933">''An '''aquifer''' is a layer of porous substrate that contains and transmits groundwater.''</font></span><br/></p><p style="text-align: right"><span style="color:#008000"><font color="#009933">''An aquifer is '''confined '''<span style="font-weight: normal">when</span>overlain by a relatively impermeable layer of rock or substrate such as an aquiclude (substrate with porosity that is so low it is virtually impermeable to groundwater )or aquitard (substrate with low porosity).''</font></span></p><p style="text-align: right"><span style="color:#008000"><font color="#009933">''An aquifer is '''unconfined''' when water can flow directly between the surface and the saturated zone of an aquifer.''</font></span></p><p style="text-align: right"><span style="color:#008000"><font color="#009933">''An '''artesian well''' can be created when groundwater becomes pressurized as it flows when a confined aquifer follows a downward grade from its recharge zone.''</font></span><br/></p> |
| | + | <br/><br/><font face="Times New Roman, Times, serif"><font size="3"><font face="Arial, sans-serif"><font size="2" style="font-size: 11pt">Groundwater may flow through the substrate at different rates (e.g. 50 feet per year or 50 inches per century) depending on the permeability. Substrates may be any rock types of any grain size such as</font></font><font face="Arial, sans-serif"><font size="2" style="font-size: 11pt">sandstone, conglomerate, fractured limestone and unconsolidated sand and gravel</font></font><font face="Arial, sans-serif"><font size="2" style="font-size: 11pt">but they must be permeable and porous</font></font><font face="Arial, sans-serif"><font size="2" style="font-size: 11pt">.</font></font><font face="Arial, sans-serif"><font size="2" style="font-size: 11pt">Being fractured, even rocks like granit and shist can be aquifers. The amount of water storaged in an aquifer can vary between the seasons and from year to year</font></font></font></font>. <ref>http://imnh.isu.edu/digitalatlas/hydr/concepts/gwater/aquifer.htm [accessed 2013-12-11]</ref><br/> |
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| | + | === Global distribution of groundwater<br/> === |
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| | + | <font size="2" style="font-size: 11pt">Due to climatic conditions and geology the global distribution of groundwater varies. The figure illustrates the amounts of groundwater hold by different regions of the world. Asia and Africa provide the greatest groundwater resources, followed by North America and South America. Europe and Australia possess the smallest groundwater resources.</font><br/><span style="color:#008000"><span style="color:#008000"><span style="color:#008000">'''FIGURE'''</span></span> </span><u>Global groundwater resources</u><span style="color:#008000"><span style="color:#008000">(''<font color="#009933"><font size="2" style="font-size: 9pt">[http://thelivinglabiesd.files.wordpress.com/2012/11/02_freshwater_regions1-302x1024-copy.jpg http://thelivinglabiesd.files.wordpress.com/2012/11/02_freshwater_regions1-302x1024-copy.jpg]</font></font>''</span></span>, accessed 2013-12-16)<br/> |
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| | + | <font size="2" style="font-size: 9pt">'''<font size="2" style="font-size: 11pt"><span style="font-style: normal"><span style="font-weight: normal">Only limited quantities of groundwater are provided by local and shallow aquifers. Areas in green symbolize more complex basins which might comsist of multiple aquifers separated by impermeable rock or include layers of saltwater as well as freshwater. Major groundwater basins (in blue) provide abundant, relatively easily extractable groundwater resources.</span></span></font>'''</font><br/> |
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| | + | <span style="color:#008000"><span style="color:#008000">'''<span style="color:#008000">FIGURE</span>'''</span> </span><u>Global groundwater resources, aquifers </u><span style="color:#008000"><span style="color:#008000"><span style="color:#008000">(<span style="color:#0000ff">''[http://ensia.com/wp-content/uploads/2013/07/feature_groundwater_inline_map2_large.jpg http://ensia.com/wp-content/uploads/2013/07/feature_groundwater_inline_map2_large.jpg]''</span></span></span></span>, accessed 2013-12-16)<br/> |
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| | + | === Groundwater recharge<br/> === |
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| | + | '''<font size="2" style="font-size: 11pt"><span style="font-style: normal"><span style="font-weight: normal">The replenishment of groundwater can occur through rain, snow and surface waters. The recharge rate varies tremendously from place to place</span></span></font>''''''<font size="2" style="font-size: 11pt"><span style="font-style: normal"><span style="font-weight: normal">due to a different</span></span></font>''''''<font size="2" style="font-size: 11pt"><span style="font-style: normal"><span style="font-weight: normal">geology and climate.</span></span></font>''''''<font size="2" style="font-size: 11pt"><span style="font-style: normal"><span style="font-weight: normal">Depending of aquifer size and type the recharge rate determines the extent to which groundwater withdrawl happens in a sustainable scale.</span></span></font>''''''<font size="2" style="font-size: 11pt"><span style="font-style: normal"><span style="font-weight: normal">The biggest areas with the highest</span></span></font>''''''<font size="2" style="font-size: 11pt"><span style="font-style: normal"><span style="font-weight: normal">recharge rates occur in Indonesia, in Papua New Guinea, in the Democratic Rebublic of the Congo and in the Amazonas region.</span></span></font>''''''<font size="2" style="font-size: 11pt"><span style="font-style: normal"><span style="font-weight: normal">Regions with the lowest recharge rates are Nevada, the Sahara, Yemen, Oman, parts of Saudi Arabia, and parts of East China.</span></span></font>'''<br/> |
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| | + | <span style="color:#008000">'''FIGURE'''</span> <u>Groundwater recharge, world </u><span style="display: none" data-cke-bookmark="1"></span>'''[http://ensia.com/wp-content/uploads/2013/07/feature_groundwater_inline_map1_large.jpg (]'''<span style="display: none" data-cke-bookmark="1"></span>''[http://ensia.com/wp-content/uploads/2013/07/feature_groundwater_inline_map1_large.jpg http://ensia.com/wp-content/uploads/2013/07/feature_groundwater_inline_map1_large.jpg]'', accessed 2013-12-16)<br/> |
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| | + | === Groundwater pollution<br/> === |
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| | + | Groundwater quality is most commonly affected by waste disposal but also from agricultural activities, groundwaster development, mining, spills, leakage from underground pipes and tanks, and road salting. Due to the slow residence time (turnover) of groundwater, effects of pollution may remain in the aquifers for years, decades, or centuries.<ref>A. Zaporozec Dr. (1981) Ground-Water pollution and its sources. GeoJournal 5(5); 457-471</ref><br/> |
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| | + | === Groundwater and agriculture<br/> === |
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| | + | Agriculture takes up about 60 % of groundwater withdrawn whereas the remaining 40 % are almost equally divided between the industrial and domestic sectors.<ref>Vrba, J., and J. van der Gun. 2004. The World’s Groundwater Resources, http://www.un-igrac.org/dynamics/modules/SFIL0100/view.php?fil_Id=126</ref> Poor drainage of soils can lead to rising water tables which come to the surface in low-lying areas. Those can result in major land degradation problems of waterlogging and soil salinity and increasing levels of salt in surface waters.<ref>Agricultural Drainage Criteria. Oosterbaan, On website www.waterlog.info, Chapter 17 in: H.P.Ritzema (Ed.), Drainage Principles and Applications. International Institute for Land Reclamation and Improvement ( ILRI), Publication 16, second revised edition, 1994, Wageningen, The Netherlands. ISBN 90 70754 3 39 [accessed 2013-12-12]</ref> Consequently, major damage has occurred to economies and environments.<ref>Ludwig, D.; Hilborn, R.; Walters, C. (1993). "Uncertainty, Resource Exploitation, and Conservation: Lessons from History". Science 260 (5104): 17–36.</ref> |
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| | + | = References = |
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| | + | <br/><references /><br/> |
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