Difference between revisions of "Hydrology" - New World Encyclopedia

From New World Encyclopedia
(precipitation vs. rainfall)
(added credit and category tags, deleted foreign language links)
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[[Image:Land_ocean_ice_cloud_1024.jpg|thumb|250px|Water covers 70% of the Earth's surface.]]
 
[[Image:Land_ocean_ice_cloud_1024.jpg|thumb|250px|Water covers 70% of the Earth's surface.]]
  
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'''Hydrology''' (from [[Greek_language|Greek]]: Yδρoλoγια, Yδωρ+Λoγos, ''Hydrologia'', the "study of water") is the study of the movement and distribution of [[water]] throughout the Earth, and thus addresses both the [[hydrologic cycle]] and [[water resources]]. A practitioner of hydrology is a hydrologist, working within the fields of either [[earth science|earth]] or [[environmental science]], or [[civil engineering|civil]] and [[environmental engineering]].
+
'''Hydrology''' (from [[Greek language|Greek]]: Yδρoλoγια, Yδωρ+Λoγos, ''Hydrologia'', the "study of water") is the study of the movement, distribution, and quality of [[water]] throughout the Earth, and thus addresses both the [[hydrologic cycle]] and [[water resources]]. A practitioner of hydrology is a hydrologist, working within the fields of either [[earth science|earth]] or  or [[environmental science]], [[physical geography]] or [[civil engineering|civil]] and [[environmental engineering]].
  
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Domains of hydrology include [[hydrometeorology]], [[surface-water hydrology|surface hydrology]], and [[hydrogeology]], where water plays the central role. [[Oceanography]] and [[meteorology]] are not included because water is only one of many important aspects.
+
Domains of hydrology include [[hydrometeorology]], [[surface-water hydrology|surface hydrology]], [[hydrogeology]], [[drainage basin]] management and [[water quality]], where water plays the central role. [[Oceanography]] and [[meteorology]] are not included because water is only one of many important aspects.
  
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Hydrological research is useful not only in that it allows us to better understand the world in which we live, but also by providing insight for [[environmental engineering]], [[environmental policy|policy]] and [[environmental planning|planning]].  
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Hydrological research is useful in that it allows us to better understand the world in which we live, and also provides insight for [[environmental engineering]], [[environmental policy|policy]] and [[environmental planning|planning]].  
  
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==History==
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==Hydrologic cycle==
  
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Hydrology has been a subject of investigation and engineering for millennia. For example, in about 4000 B.C.E. the [[Nile]] was dammed to improve agricultural productivity of previously barren lands. [[Mesopotamia|Mesopotamian]] towns were protected from flooding with high earthen walls. [[Aquaducts]] were built by the [[Ancient Greece|Greeks]] and [[Ancient Rome|Romans]], while the [[History of China|Chinese]] built irrigation and flood control works.
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''Main article: [[Hydrologic cycle]]''
  
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[[Vitruvius|Marcus Vitruvius]], in the first century B.C.E., described a philosophical theory of the hydrologic cycle, in which precipitation falling in the mountains infiltrated the earth's surface and led to streams and springs in the lowlands. With adoption of a more scientific approach, [[Leonardo da Vinci]] and [[Bernard Palissy]] independantly reached an accurate representation of the hydrologic cycle. It was not until the 17th century that hydrologic variables began to be quantified.
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==Branches of hydrology==
 +
'''[[Chemical hydrology]]''' is the study of the chemical characteristics of water.
  
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Pioneers of the modern science of hydrology include [[Pierre Perrault]], [[Edme Mariotte]], and [[Edmund Halley]]. By measuring rainfall, runoff, and drainage area, Perrault showed that precipitation was sufficient to account for the flow of the [[Seine]] River. Marriotte combined velocity and river cross-section measurements to obtain discharge, again in the Seine. Halley showed that the evaporation from the [[Mediterranean Sea]] was sufficient to account for the outflow of rivers flowing into the sea.
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'''[[Ecohydrology]]''' is the study of interactions between organisms and the hydrologic cycle.
  
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Advances in the 18th century included the Bernoulli piezometer and [[Bernoulli's equation]], by [[Daniel Bernoulli]], the [[Pitot tube]], and the Chezy formula. The 19th century saw development in groundwater hydrology, including [[Darcy's law]], the Dupuit-Thiem well formula, and Hagen-Poiseuille's capillary flow equation.
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'''[[Hydrogeology]]''' is the study of the presence and movement of water in aquifers.
  
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Rational analyses began to replace empiricism in the 20th century, while governmental agencies began their own hydrological research programs. Of particular importance were Leroy Sherman's unit hydrograph, the infiltration theory of [[Robert E. Horton]], and C.V. Theis's [[Aquifer test|equation]] describing well hydraulics.
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'''[[Hydroinformatics]]''' is the adaptation of information technology to hydrology and water resources applications.
  
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Since the [[1950s]], hydrology has been approached with a more theoretical basis than in the past, facilitated by advances in the physical understanding of hydrological processes and by the advent of [[computer]]s.
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'''[[Hydrometeorology]]''' is the study of the transfer of water and energy between land and water body surfaces and the lower atmosphere.
  
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==Hydrologic Cycle==
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'''[[Hydromorphology]]'''
  
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''Main article: [[Hydrologic cycle]]''
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'''[[Isotope hydrology]]''' is the study of the isotopic signatures of water.
 +
 
 +
'''[[Surface-water hydrology|Surface hydrology]]''' is the study of hydrologic processes that operate at or near the [[Earth]]'s surface.
  
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The central theme of hydrology is that water moves throughout the Earth in different ways and at different rates. The most vivid image of this is in the evaporation of water from the ocean, which forms clouds. These '''clouds drift over the land''' and produce rain, which flows down the rivers back to the ocean, completing a cycle.
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===Related fields===
 +
*[[Aquatic chemistry]]
 +
*[[Civil engineering]]
 +
*[[Climatology]]
 +
*[[Environmental engineering]]
 +
*[[Physical Geography]]
 +
*[[Geomorphology]]
 +
*[[Hydraulic engineering]]
 +
*[[Limnology]]
 +
*[[Oceanography]]
  
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==Hydrologic Measurements==
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==Hydrologic measurements==
  
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The movement of water through the Earth can be measured in a number of ways. This information is important for both assessing water resources and understanding the processes involved in the hydrologic cycle. The following is a list of devices used by hydrologists and what they measure.
+
The movement of water through the Earth can be measured in a number of ways. This information is important for both assessing water resources and understanding the processes involved in the hydrologic cycle. Following is a list of devices used by hydrologists and what they are used to measure.
  
−
* [[Rain gauge]] - rain and snowfall
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* [[Disdrometer]] - precipitation characteristics
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* [[stream gage|Stream gauge]] - stream flow (see: [[discharge (hydrology)]])
+
* [[Evaporation]] -[[Symon]]'s evaporation pan
 +
* [[Infiltrometer]] - infiltration
 +
* [[Piezometer]] - groundwater pressure and, by inference, groundwater depth (see: [[aquifer test]])
 
* [[Radar]] - cloud properties
 
* [[Radar]] - cloud properties
−
* [[Piezometer]] - groundwater pressure and, by inferrence, groundwater depth (see: [[aquifer test]])
+
* [[Rain gauge]] - rain and snowfall
 +
* [[Satellite]]
 +
* [[Sling psychrometer]] - humidity
 +
* [[Stream gauge]] - stream flow (see: [[discharge (hydrology)]])
 
* [[Tensiometer]] - [[soil moisture]]
 
* [[Tensiometer]] - [[soil moisture]]
−
* '''[[Satellite]]'''
 
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* [[Disdrometer]] - precipitation characteristics
 
 
* [[Time domain reflectometer]] - [[soil moisture]]
 
* [[Time domain reflectometer]] - [[soil moisture]]
−
* [[Sling psychrometer]] - humidity
 
−
* [[Infiltrometer]] - infiltration
 
  
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==Hydrologic Prediction==
+
==Hydrologic prediction==
  
 
Observations of hydrologic processes are used to make [[predictions]] of future water movement and quantity.
 
Observations of hydrologic processes are used to make [[predictions]] of future water movement and quantity.
  
−
===Statistical Hydrology===
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===Statistical hydrology===
 +
 
 +
By analysing the [[Statistics|statistical]] properties of hydrologic records, such as rainfall or river flow, hydrologists can estimate future hydrologic phenomena. This, however, assumes the characteristics of the processes remain unchanged.
  
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By analysing the [[Statistics|statistical]] properties of hydrologic records, such as rainfall or river flow, hydrologists can estimate future hydrologic phenomena. This, however, assumes the characteristics of the processes remain unchanged.
+
These estimates are important for [[engineers]] and [[economists]] so that proper [[risk analysis]] can be performed to influence investment decisions in future infrastructure and to determine the yield reliability characteristics of water supply systems. Statistical information is utilised to formulate [[operating rules]] for [[large dams]] forming part of systems which include [[agricultural]], [[Industry|industrial]] and [[residential]] demands.
  
 
See: [[return period]].
 
See: [[return period]].
  
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===Hydrologic Modeling===
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===Hydrologic modeling===
  
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With an understanding of how changes in the environment affect the movement of water, hydrologists can also construct models to predict '''how these changes will happen''' in the future.
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Hydrologic models are simplified, conceptual representations of a part of the hydrologic cycle. They are primarily used for hydrologic prediction and for understanding hydrologic processes. Two major types of hydrologic models can be distinguished:
  
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==Hydrologic Transport==
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* Models based on data. These models are [[Black box (systems)|black box]] systems, using mathematical and statistical concepts to link a certain input (for instance [[rainfall]]) to the model output (for instance [[runoff]]). Commonly used techniques are [[regression]], [[transfer function]]s, [[neural networks]] and [[system identification]].  These models are known as stochastic hydrology models.
  
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Water movement is a significant means by which other material, such as soil or pollutants, are transported from place to place.
+
* Models based on process descriptions. These models try to represent the physical processes observed in the real world. Typically, such models contain representations of [[surface runoff]], [[subsurface flow]], [[evapotranspiration]], and [[open channel flow|channel flow]], but they can be far more complicated.  These models are known as deterministic hydrology models.  Deterministic hydrology models can be subdivided into single-event models and continuous simulation models.
  
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See: [[erosion]], [[pollution]].
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==Hydrologic transport==
  
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==Applications of Hydrology==
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:''See main article: '''[[Hydrologic transport model]]'''
 +
 
 +
Water movement is a significant means by which other material, such as soil or pollutants, are transported from place to place. Initial input to receiving waters may arise from a [[point source]] discharge or a [[line source]] or [[area source]], such as [[surface runoff]].  Since the 1960s rather complex [[mathematical model]]s have been developed, facilitated by the availability of high speed computers.  The most common pollutant classes analyzed are [[nutrient]]s, [[pesticide]]s, [[total dissolved solids]] and [[sediment]].
 +
 
 +
==Applications of hydrology==
  
 
* Mitigating and predicting [[flood]], [[landslide]] and [[drought]] risk;
 
* Mitigating and predicting [[flood]], [[landslide]] and [[drought]] risk;
Line 69: Line 88:
 
* Designing [[dams]] for [[water supply]] or [[hydroelectricity|hydroelectric power]] generation;
 
* Designing [[dams]] for [[water supply]] or [[hydroelectricity|hydroelectric power]] generation;
 
* Designing [[bridges]];
 
* Designing [[bridges]];
 +
* Designing [[sewers]] and [[urban drainage system]];
 +
* Analyzing the impacts of [[antecedent moisture]] on sanitary sewer systems.
 
* Predicting [[geomorphology|geomorphological]] changes, such as [[erosion]] or [[sedimentation]].
 
* Predicting [[geomorphology|geomorphological]] changes, such as [[erosion]] or [[sedimentation]].
 
* Assessing the impacts of natural and anthropogenic environmental change on [[water resources]].
 
* Assessing the impacts of natural and anthropogenic environmental change on [[water resources]].
 
* Assessing [[pollution|contaminant]] transport risk and establishing environmental policy guidelines.
 
* Assessing [[pollution|contaminant]] transport risk and establishing environmental policy guidelines.
  
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==See also==
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== References ==
  
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* [[chemical hydrology]]
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* Introduction to Hydrology, 4e. Viessman and Lewis, 1996.  ISBN 0-673-99337-X
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* [[current (water)]]
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* Handbook of Hydrology.  ISBN 0-07-039732-5
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* [[drainage system]]
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* Encyclopedia of Hydrological Sciences.  ISBN 0-471-49103-9
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* [[ecohydrology]]
 
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* [[fresh water]]
 
−
* [[groundwater]]
 
−
* [[hydraulic engineering]]
 
−
* [[hydrograph]]
 
−
* [[hydroinformatics]]
 
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* [[hyetograph]]
 
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* [[isotope hydrology]]
 
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* [[limnology]]
 
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* [[river]]
 
−
* [[soil moisture]]
 
−
* [[virtual water]]
 
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* [[water abstraction]]
 
−
* [[water industry]]
 
−
* [[water table]]
 
−
* [[watershed]]
 
−
* [[well water]]
 
  
−
==References==
+
== External links ==
  
−
* Introduction to Hydrology, 4e. Viessman and Lewis, 1996. ISBN 0-673-99337-X
+
* [http://www.cig.ensmp.fr/~hubert/glu/aglo.htm International Glossary of Hydrology].
−
* Handbook of Hydrology. ISBN 0070397325
+
* [http://www.usgs.gov U.S. Geological Survey] - [http://water.usgs.gov Water Resources of the United States]
 +
* [http://www.hydrology.org.uk/ British Hydrology Society]
 +
* [http://www.hydrology.uni-freiburg.de/ihf_home-e.htm Institute of Hydrology, Albert-Ludwigs-University of Freiburg, Germany]
 +
* [http://www.weather.gov/ohd/ NOAA's National Weather Service - Office of Hydrologic Development]
 +
* [http://hydram.epfl.ch/VICAIRE/ Virtual Campus in Hydrology and Water Resources]
 +
* [http://www.floodrisk.net Decision tree to choose an uncertainty method for hydrological and hydraulic modelling]
  
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==External links and sources==
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{{Earth science}}
−
*[http://www.cig.ensmp.fr/~hubert/glu/aglo.htm International Glossary of Hydrology].
+
{{Environmental science}}
−
*[http://www.usgs.gov U.S. Geological Survey].
+
{{Physical geography topics}}
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*[http://www.hydrology.org.uk/ British Hydrology Society]
 
  
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[[Category:Physical sciences]]
 +
[[Category:Earth sciences]]
 
[[Category:Civil engineering]]
 
[[Category:Civil engineering]]
 
[[Category:Environmental engineering]]
 
[[Category:Environmental engineering]]
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[[Category:Earth sciences]]
 
 
[[Category:Physical geography]]
 
[[Category:Physical geography]]
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[[category:Life sciences]]
 
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[[Category:Physical sciences]]
 
  
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{{credit|23627846}}
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{{credit|73715906}}

Revision as of 14:17, 5 September 2006

Water covers 70% of the Earth's surface.

Hydrology (from Greek: Yδρoλoγια, Yδωρ+Λoγos, Hydrologia, the "study of water") is the study of the movement, distribution, and quality of water throughout the Earth, and thus addresses both the hydrologic cycle and water resources. A practitioner of hydrology is a hydrologist, working within the fields of either earth or or environmental science, physical geography or civil and environmental engineering.

Domains of hydrology include hydrometeorology, surface hydrology, hydrogeology, drainage basin management and water quality, where water plays the central role. Oceanography and meteorology are not included because water is only one of many important aspects.

Hydrological research is useful in that it allows us to better understand the world in which we live, and also provides insight for environmental engineering, policy and planning.

Hydrologic cycle

Main article: Hydrologic cycle

Branches of hydrology

Chemical hydrology is the study of the chemical characteristics of water.

Ecohydrology is the study of interactions between organisms and the hydrologic cycle.

Hydrogeology is the study of the presence and movement of water in aquifers.

Hydroinformatics is the adaptation of information technology to hydrology and water resources applications.

Hydrometeorology is the study of the transfer of water and energy between land and water body surfaces and the lower atmosphere.

Hydromorphology

Isotope hydrology is the study of the isotopic signatures of water.

Surface hydrology is the study of hydrologic processes that operate at or near the Earth's surface.

Related fields

Hydrologic measurements

The movement of water through the Earth can be measured in a number of ways. This information is important for both assessing water resources and understanding the processes involved in the hydrologic cycle. Following is a list of devices used by hydrologists and what they are used to measure.

  • Disdrometer - precipitation characteristics
  • Evaporation -Symon's evaporation pan
  • Infiltrometer - infiltration
  • Piezometer - groundwater pressure and, by inference, groundwater depth (see: aquifer test)
  • Radar - cloud properties
  • Rain gauge - rain and snowfall
  • Satellite
  • Sling psychrometer - humidity
  • Stream gauge - stream flow (see: discharge (hydrology))
  • Tensiometer - soil moisture
  • Time domain reflectometer - soil moisture

Hydrologic prediction

Observations of hydrologic processes are used to make predictions of future water movement and quantity.

Statistical hydrology

By analysing the statistical properties of hydrologic records, such as rainfall or river flow, hydrologists can estimate future hydrologic phenomena. This, however, assumes the characteristics of the processes remain unchanged.

These estimates are important for engineers and economists so that proper risk analysis can be performed to influence investment decisions in future infrastructure and to determine the yield reliability characteristics of water supply systems. Statistical information is utilised to formulate operating rules for large dams forming part of systems which include agricultural, industrial and residential demands.

See: return period.

Hydrologic modeling

Hydrologic models are simplified, conceptual representations of a part of the hydrologic cycle. They are primarily used for hydrologic prediction and for understanding hydrologic processes. Two major types of hydrologic models can be distinguished:

  • Models based on data. These models are black box systems, using mathematical and statistical concepts to link a certain input (for instance rainfall) to the model output (for instance runoff). Commonly used techniques are regression, transfer functions, neural networks and system identification. These models are known as stochastic hydrology models.
  • Models based on process descriptions. These models try to represent the physical processes observed in the real world. Typically, such models contain representations of surface runoff, subsurface flow, evapotranspiration, and channel flow, but they can be far more complicated. These models are known as deterministic hydrology models. Deterministic hydrology models can be subdivided into single-event models and continuous simulation models.

Hydrologic transport

See main article: Hydrologic transport model

Water movement is a significant means by which other material, such as soil or pollutants, are transported from place to place. Initial input to receiving waters may arise from a point source discharge or a line source or area source, such as surface runoff. Since the 1960s rather complex mathematical models have been developed, facilitated by the availability of high speed computers. The most common pollutant classes analyzed are nutrients, pesticides, total dissolved solids and sediment.

Applications of hydrology

  • Mitigating and predicting flood, landslide and drought risk;
  • Designing irrigation schemes and managing agricultural productivity;
  • Providing drinking water;
  • Designing dams for water supply or hydroelectric power generation;
  • Designing bridges;
  • Designing sewers and urban drainage system;
  • Analyzing the impacts of antecedent moisture on sanitary sewer systems.
  • Predicting geomorphological changes, such as erosion or sedimentation.
  • Assessing the impacts of natural and anthropogenic environmental change on water resources.
  • Assessing contaminant transport risk and establishing environmental policy guidelines.

References
ISBN links support NWE through referral fees

External links

General subfields within the earth sciences
Atmospheric sciences | Geodesy | Geology | Geophysics | Glaciology
Hydrology | Oceanography | Soil science
Environmental science
Atmospheric sciences | Ecology | Geosciences | Soil science| Hydrology |
Related fields: Biology | Chemistry | Environmental design | Environmental economics | Environmental ethics | Environmental law | Physics |

Sustainability | Waste management

Environmental technology


 Physical geography
Land ocean ice cloud 1024.jpg Biogeography · Climatology & paleoclimatology · Coastal/Marine studies · Geodesy · Geomorphology · Glaciology · Hydrology & Hydrography · Landscape ecology · Limnology · Oceanography · Palaeogeography · Pedology · Quaternary Studies

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