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. ImageMetadata File history File links Download high resolution version (1024x512, 222 KB) Land surface, ocean color, sea ice and clouds. ... ImageMetadata File history File links Download high resolution version (1024x512, 222 KB) Land surface, ocean color, sea ice and clouds. ... Impact of a drop of water. ... The water cycle—technically known as the hydrologic cycle—is the circulation of water within the earths hydrosphere, involving changes in the physical state of water between liquid, solid, and gas phases. ... Water resources are sources of water that are useful or potentially useful to humans. ... Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. ... jecca is very beautiful!! Environmental science is the study of the interactions among the physical, chemical and biological components of the environment; with a focus on pollution and degradation of the environment related due to human activities; and the impact on biodiversity and sustainability from local and global development. ... Physical geography or physiogeography is a subfield of geography that focuses on the systematic study of patterns and processes within the hydrosphere, biosphere, atmosphere, and lithosphere. ... The Falkirk Wheel in Scotland. ... Environmental engineering is the application of science and engineering principles to improving the environment (air, water, and/or land resources), to provide healthful water, air and land for human habitation and for other organisms, and to investigate the possibilities for remediation of polluted sites. ...

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. Hydrometeorology is a branch of meteorology and hydrology that studies the transfer of water and energy between the land surface and the lower atmosphere. ... Surface water hydrology describes the relation between rainfall and runoff, which is important for water resources for drinking water, agriculture and the environment, and for protecting and safe-guarding people against possible floods. ... Hydrogeology (hydro- meaning water, and -geology meaning the study of rocks) is the part of hydrology that deals with the distribution and movement of groundwater in the soil and rocks of the Earths crust (commonly in aquifers). ... A drainage basin is the area within the drainage basin divide (yellow outline), and drains the surface runoff and river discharge (blue lines) of a contiguous area. ... To most people not professionally involved in water quality issues, water is either drinkable (technically potable) or contains potentially harmful or toxic substances. ... Thermohaline circulation Oceanography (from Ocean + Greek γράφειν = write), also called oceanology or marine science is the study of the Earths oceans and seas. ... Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ...

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. Environmental engineering is the application of science and engineering principles to improving the environment (air, water, and/or land resources), to provide healthful water, air and land for human habitation and for other organisms, and to investigate the possibilities for remediation of polluted sites. ... Environmental policy refers to the laws, regulations, and other policy mechanisms concerning environmental issues and sustainability. ... Environmental planning is a relatively new field of study that aims to merge the practice of urban planning with the concerns of environmentalism. ...

Hydrologic cycle

Main article: Hydrologic cycle The water cycle—technically known as the hydrologic cycle—is the circulation of water within the earths hydrosphere, involving changes in the physical state of water between liquid, solid, and gas phases. ...

Branches of hydrology

Chemical hydrology is the study of the chemical characteristics of water. Chemical hydrology or hydrochemistry is the subdivion of hydrology that deals with the chemical characteristics of water. ...

Ecohydrology is the study of interactions between organisms and the hydrologic cycle. Ecohydrology is a sub-discipline of hydrology that focuses on ecological processes involved in the hydrological cycle. ...

Hydrogeology is the study of the presence and movement of water in aquifers. Hydrogeology (hydro- meaning water, and -geology meaning the study of rocks) is the part of hydrology that deals with the distribution and movement of groundwater in the soil and rocks of the Earths crust (commonly in aquifers). ...

Hydroinformatics is the adaptation of information technology to hydrology and water resources applications. Hydroinformatics is a branch of Informatics which concentrates on the application of information and communications technologies (ICTs) in addressing the increasingly serious problems of the equitable and efficient use of water for many different purposes. ...

Hydrometeorology is the study of the transfer of water and energy between land and water body surfaces and the lower atmosphere. Hydrometeorology is a branch of meteorology and hydrology that studies the transfer of water and energy between the land surface and the lower atmosphere. ...

Hydromorphology

Isotope hydrology is the study of the isotopic signatures of water. Isotope hydrology is a fast, cheap, and reliable way to discover the age, origins, size, flow and fate of a water source for purposes of sound water-use policy, maping underground aquifers, conserving water supplies, and controling pollution. ...

Surface hydrology is the study of hydrologic processes that operate at or near the Earth's surface. Surface water hydrology describes the relation between rainfall and runoff, which is important for water resources for drinking water, agriculture and the environment, and for protecting and safe-guarding people against possible floods. ... Earth (often referred to as the Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ...

Related fields

• Aquatic chemistry
• Civil engineering
• Climatology
• Environmental engineering
• Physical Geography
• Geomorphology
• Hydraulic engineering
• Limnology
• Oceanography

Aquatic chemistry is the study of chemical reactions in aqueous solutions, including acid-base reactions, redox reactions, and precipitation-dissolution reactions. ... The Falkirk Wheel in Scotland. ... Climatology is the study of climate, and is a branch of the atmospheric sciences. ... Environmental engineering is the application of science and engineering principles to improving the environment (air, water, and/or land resources), to provide healthful water, air and land for human habitation and for other organisms, and to investigate the possibilities for remediation of polluted sites. ... Physical geography or physiogeography is a subfield of geography that focuses on the systematic study of patterns and processes within the hydrosphere, biosphere, atmosphere, and lithosphere. ... Surface of the Earth Geomorphology is the study of landforms, including their origin and evolution, and the processes that shape them. ... Hydraulic engineering is a sub-discipline of civil engineering concerned with the flow and conveyance of fluids, principally water. ... Limnology is a discipline that concerns the study of in-land waters (both saline and fresh), specifically lakes, ponds and rivers (both natural and manmade), including their biological, physical, chemical, and hydrological aspects. ... Thermohaline circulation Oceanography (from Ocean + Greek γράφειν = write), also called oceanology or marine science is the study of the Earths oceans and seas. ...

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

A disdrometer is an instrument used to measure the drop size distribution and velocity of falling precipitation. ... Water vapor condensing over a cup of hot tea Evaporation is one of the two forms of vaporization. ... A double ring infiltrometer is a tool for measuring how quickly a soil can take in water, also known as the rate of infiltration into the soil. ... Piezometer is a device used for the measurement of hydraulic head in aquifers. ... An Aquifer test is conducted to evaluate an aquifer by stimulating the aquifer through constant pumping, and observing the aquifers response (drawdown) in observation wells. ... This long range radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to detect, determine the distance of, and map, objects such... Standard Rain Gauge Tipping Bucket Rain Gauge Recorder Close up of a Tipping Bucket Rain Gauge Recorder chart A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid or solid (snow, sleet, hail) precipitation over a set period of... A satellite is any object that orbits another object (which is known as its primary). ... Hygrometers are instruments used for measuring humidity. ... A stream gage refers to a site along a stream where measurements of volumetric discharge (flow) are made. ... In hydrology, the discharge of a river is the volume of water transported by it in a certain amount of time. ... A tensiometer is a device used to determine soil moisture tension, an indirect measure of soil moisture content. ... This article or section does not cite its references or sources. ... In telecommunication, a time-domain reflectometer (TDR) is an electronic instrument used to characterize and locate faults in metallic cables ( twisted pair, coax). ... This article or section does not cite its references or sources. ...

Hydrologic prediction

Observations of hydrologic processes are used to make predictions of future water movement and quantity. Prediction of future events is an ancient human wish. ...

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. A graph of a bell curve in a normal distribution showing statistics used in educational assessment, comparing various grading methods. ...

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. Engineering is the application of scientific and technical knowledge to solve human problems. ... Economists are scholars conducting research in the field of economics. ... Risk analysis is a technique to identify and assess factors that may jeopardize the success of a project or achieving a goal. ... A residential area is a type of land use where the predominant use is residential. ...

See: return period. A return period also known as a recurrence interval is an estimate of the liklihood of a flood or river discharge flow of a certain size. ...

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.

Black box is technical jargon for a device or system or object when it is viewed primarily in terms of its input and output characteristics. ... In meteorology, precipitation is any kind of water that falls from the sky as part of the weather. ... Run-off or runoff may refer to one of the following. ... Generally, regression is a move backwards; It is the opposite of progress. ... A transfer function is a mathematical representation of the relation between the input and output of a linear time-invariant system. ... A neural network is an interconnected group of neurons. ... System identification is a general term to describe mathematical tools and algorithms that build dynamical models from measured data. ... Runoff flowing into a stormwater drain Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component of the water cycle[1][2]. Runoff that occurs on surfaces before reaching a channel is also called overland flow. ... Evapotranspiration (ET) is the sum of evaporation and plant transpiration. ... The Manning formula is an empirical formula for open channel flow, or flow driven by gravity. ...

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. A point source may be a source of light that is treated as having no physical extension, or a source in fluid flow, or in electrostatics, or a source of pollution coming from a single cause, such as a municipal plant. ... Runoff flowing into a stormwater drain Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component of the water cycle[1][2]. Runoff that occurs on surfaces before reaching a channel is also called overland flow. ... A mathematical model is an abstract model that uses mathematical language to describe the behaviour of a system. ... // Nutrients and the body A nutrient is any element or compound necessary for or contributing to an organisms metabolism, growth, or other functioning. ... A cropduster spreading pesticide. ... Total Dissolved Solids (TDS) is that portion of solids in water that can pass through a 2 micrometre filter. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ...

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.

Look up flood in Wiktionary, the free dictionary. ... Landslide of soil and regolith in Pakistan A landslide is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows. ... A drought or an extreme dry periodic climate is an extended period where water availability falls below the statistical requirements for a region. ... High-altitude aerial view of irrigation in the Heart of the Sahara (, ) Irrigation (in agriculture) is the replacement or supplementation of rainfall with water from another source in order to grow crops. ... Drinking water Drinking water is water that is intended to be drunk by humans. ... DAMS is a racing team from France, involved in many areas of motorsports. ... A water supply system provides water to the locations that need it. ... Hydraulic turbine and electrical generator. ... This article is about the edifice. ... Sewers transport wastewater from buildings to treatment facilities. ... Surface of the Earth Geomorphology is the study of landforms, including their origin and evolution, and the processes that shape them. ... Severe soil erosion in a wheat field near Washington State University, USA. Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water or ice, by downward or down-slope movement in response to gravity or by living organisms (in the case of... Sedimentation describes the motion of particles in solutions or suspensions in response to an external force such as gravity, centrifugal force or electric force. ... Water resources are sources of water that are useful or potentially useful to humans. ... Water pollution Pollution is the release of chemical, physical, biological or radioactive contaminants to the environment. ...

References

• Introduction to Hydrology, 4e. Viessman and Lewis, 1996. ISBN 0-673-99337-X
• Handbook of Hydrology. ISBN 0-07-039732-5
• Encyclopedia of Hydrological Sciences. ISBN 0-471-49103-9

External links

• International Glossary of Hydrology.
• U.S. Geological Survey - Water Resources of the United States
• British Hydrology Society
• Institute of Hydrology, Albert-Ludwigs-University of Freiburg, Germany
• NOAA's National Weather Service - Office of Hydrologic Development
• Virtual Campus in Hydrology and Water Resources
• Decision tree to choose an uncertainty method for hydrological and hydraulic modelling

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