Hydrology

Hydrology

Overview
Hydrology is the study of the movement, distribution, and quality of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 on Earth and other planets, including the hydrologic cycle, water resources
Water resources
Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water....

 and environmental watershed sustainability. A practitioner of hydrology is a hydrologist, working within the fields of earth
Earth science
Earth science is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth sciences...

 or environmental science
Environmental science
Environmental science is an interdisciplinary academic field that integrates physical and biological sciences, to the study of the environment, and the solution of environmental problems...

, physical geography
Physical geography
Physical geography is one of the two major subfields of geography. Physical geography is that branch of natural science which deals with the study of processes and patterns in the natural environment like the atmosphere, biosphere and geosphere, as opposed to the cultural or built environment, the...

, geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

 or civil
Civil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...

 and environmental engineering
Environmental engineering
Environmental engineering is the application of science and engineering principles to improve the natural environment , to provide healthy water, air, and land for human habitation and for other organisms, and to remediate polluted sites...

.

Domains of hydrology include hydrometeorology
Hydrometeorology
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 hydrology
Surface-water hydrology
Surface-water hydrology is a field that encompasses all surface waters of the globe...

, hydrogeology
Hydrogeology
Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust, . The term geohydrology is often used interchangeably...

, drainage basin
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 management and water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

, where water plays the central role.
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Encyclopedia
Hydrology is the study of the movement, distribution, and quality of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 on Earth and other planets, including the hydrologic cycle, water resources
Water resources
Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water....

 and environmental watershed sustainability. A practitioner of hydrology is a hydrologist, working within the fields of earth
Earth science
Earth science is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth sciences...

 or environmental science
Environmental science
Environmental science is an interdisciplinary academic field that integrates physical and biological sciences, to the study of the environment, and the solution of environmental problems...

, physical geography
Physical geography
Physical geography is one of the two major subfields of geography. Physical geography is that branch of natural science which deals with the study of processes and patterns in the natural environment like the atmosphere, biosphere and geosphere, as opposed to the cultural or built environment, the...

, geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

 or civil
Civil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...

 and environmental engineering
Environmental engineering
Environmental engineering is the application of science and engineering principles to improve the natural environment , to provide healthy water, air, and land for human habitation and for other organisms, and to remediate polluted sites...

.

Domains of hydrology include hydrometeorology
Hydrometeorology
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 hydrology
Surface-water hydrology
Surface-water hydrology is a field that encompasses all surface waters of the globe...

, hydrogeology
Hydrogeology
Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust, . The term geohydrology is often used interchangeably...

, drainage basin
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 management and water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

, where water plays the central role. Oceanography
Oceanography
Oceanography , also called oceanology or marine science, is the branch of Earth science that studies the ocean...

 and meteorology
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...

 are not included because water is only one of many important aspects within those fields.

Hydrological research can inform environmental engineering
Environmental engineering
Environmental engineering is the application of science and engineering principles to improve the natural environment , to provide healthy water, air, and land for human habitation and for other organisms, and to remediate polluted sites...

, policy
Environmental policy
Environmental policy is any [course of] action deliberately taken [or not taken] to manage human activities with a view to prevent, reduce, or mitigate harmful effects on nature and natural resources, and ensuring that man-made changes to the environment do not have harmful effects on...

 and planning
Environmental planning
Environmental Planning is the process of facilitating decision making to carry out development with due consideration given to the natural environmental, social, political, economic and governance factors and provides a holistic frame work to achieve sustainable outcomes.-Elements of environmental...

.

The term hydrology is from Greek: ὕδωρ, hydōr, "water"; and λόγος, logos, "study".

History of hydrology


Hydrology has been a subject of investigation and engineering for millennia. For example, about 4000 B.C. the Nile was dammed to improve agricultural productivity of previously barren lands. Mesopotamian towns
Mesopotamia
Mesopotamia is a toponym for the area of the Tigris–Euphrates river system, largely corresponding to modern-day Iraq, northeastern Syria, southeastern Turkey and southwestern Iran.Widely considered to be the cradle of civilization, Bronze Age Mesopotamia included Sumer and the...

 were protected from flooding with high earthen walls. Aqueduct
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....

s were built by the Greeks
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

 and Ancient Romans, while the history of China
History of China
Chinese civilization originated in various regional centers along both the Yellow River and the Yangtze River valleys in the Neolithic era, but the Yellow River is said to be the Cradle of Chinese Civilization. With thousands of years of continuous history, China is one of the world's oldest...

 shows they built irrigation and flood control works. The ancient Sinhalese used hydrology to build complex irrigation works in Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

, also known for invention of the Valve Pit which allowed construction of large reservoirs, anicuts and canals which still function.

Marcus Vitruvius
Vitruvius
Marcus Vitruvius Pollio was a Roman writer, architect and engineer, active in the 1st century BC. He is best known as the author of the multi-volume work De Architectura ....

, in the first century B.C., 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
Leonardo da Vinci
Leonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...

 and Bernard Palissy
Bernard Palissy
Bernard Palissy was a French Huguenot potter, hydraulics engineer and craftsman, famous for having struggled for sixteen years to imitate Chinese porcelain...

 independently reached an accurate representation of the hydrologic cycle. It was not until the 17th century that hydrologic variables began to be quantified.

Pioneers of the modern science of hydrology include Pierre Perrault, Edme Mariotte
Edme Mariotte
Edme Mariotte was a French physicist and priest.- Biography :Edme Mariotte was the youngest son of Simon Mariotte, administrator at the district Til-Châtel , and Catherine Denisot . His parents lived in Til-Châtel and had 4 other children: Jean, Denise, Claude, and Catharine...

 and Edmund Halley. By measuring rainfall, runoff, and drainage area, Perrault showed that rainfall was sufficient to account for flow of the Seine. 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.

Advances in the 18th century included the Bernoulli
Bernoulli
The Bernoullis were a family of traders and scholars from Basel, Switzerland. The founder of the family, Leon Bernoulli, immigrated to Basel from Antwerp in Flanders in the 16th century, fleeing Spanish oppression....

 piezometer
Piezometer
A piezometer is either a device used to measure static liquid pressure in a system by measuring the height to which a column of the liquid rises against gravity, or a device which measures the pressure of groundwater at a specific point...

 and Bernoulli's equation, by Daniel Bernoulli, the Pitot tube
Pitot tube
A pitot tube is a pressure measurement instrument used to measure fluid flow velocity. The pitot tube was invented by the French engineer Henri Pitot Ulo in the early 18th century and was modified to its modern form in the mid-19th century by French scientist Henry Darcy...

. The 19th century saw development in groundwater hydrology, including Darcy's law, the Dupuit-Thiem well formula, and Hagen-Poiseuille's capillary flow equation.

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.

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 computers and especially Geographic Information Systems (GIS).

Hydrologic cycle


The central theme of hydrology is that water circulates throughout the Earth through different pathways 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. The rainwater flows into lakes, rivers, or aquifers. The water in lakes, rivers, and aquifers then either evaporates back to the atmosphere or eventually flows back to the ocean, completing a cycle. Water changes its state of being several times throughout this cycle.

Branches of hydrology


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

Ecohydrology
Ecohydrology
Ecohydrology is an interdisciplinary field studying the interactions between water and ecosystems. These interactions may take place within water bodies, such as rivers and lakes, or on land, in forests, deserts, and other terrestrial ecosystems...

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

Hydrogeology
Hydrogeology
Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust, . The term geohydrology is often used interchangeably...

 is the study of the presence and movement of ground water.

Hydroinformatics
Hydroinformatics
Hydroinformatics is a branch of informatics which concentrates on the application of information and communications technologies in addressing the increasingly serious problems of the equitable and efficient use of water for many different purposes...

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

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

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

Isotope hydrology
Isotope hydrology
Isotope hydrology is a field of hydrology that uses isotopic dating to estimate the age and origins of water and of movement within the hydrologic cycle. The techniques are used for water-use policy, mapping aquifers, conserving water supplies, and controlling pollution...

 is the study of the isotopic signatures of water.

Surface hydrology
Surface-water hydrology
Surface-water hydrology is a field that encompasses all surface waters of the globe...

 is the study of hydrologic processes that operate at or near Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's surface.

Drainage basin
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 management covers water-storage, in the form of reservoirs, and flood-protection.

Water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

 includes the chemistry of water in rivers and lakes, both of pollutants and natural solutes.

Related topics


Oceanography
Oceanography
Oceanography , also called oceanology or marine science, is the branch of Earth science that studies the ocean...

 is the more general study of water in the oceans and estuaries.

Meteorology
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...

 is the more general study of the atmosphere and of weather, including precipitation as snow and rainfall.

Limnology
Limnology
Limnology , also called freshwater science, is the study of inland waters. It is often regarded as a division of ecology or environmental science. It covers the biological, chemical, physical, geological, and other attributes of all inland waters...

 is the study of lakes. It covers the biological, chemical, physical, geological, and other attributes of all inland waters (running and standing waters, both fresh and saline, natural or man-made).

Applications of hydrology

  • Determining the water balance
    Water balance
    In hydrology, a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological domains, such as a column of soil or a drainage basin....

     of a region.
  • Determining the agricultural water balance
    Hydrology (agriculture)
    Agricultural hydrology is the study of water balance components intervening in agricultural water management, notably in irrigation and drainage.-Water balance components:...

    .
  • Designing riparian restoration projects.
  • Mitigating and predicting flood
    Flood
    A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...

    , landslide
    Landslide
    A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

     and drought
    Drought
    A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...

     risk.
  • Real-time flood forecasting
    Flood forecasting
    Flood forecasting is the use of real-time precipitation and streamflow data in rainfall-runoff and streamflow routing models to forecast flow rates and water levels for periods ranging from a few hours to days ahead, depending on the size of the watershed or river basin. Flood forecasting can also...

     and flood warning
    Flood warning
    Flood warning is closely linked to the task of flood forecasting. The distinction between the two is that the outcome of flood forecasting is a set of forecast time-profiles of channel flows or river levels at various locations, while "flood warning" is the task of making use of these forecasts to...

    .
  • Designing irrigation
    Irrigation
    Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

     schemes and managing agricultural
    Agriculture
    Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

     productivity.
  • Part of the hazard module in catastrophe modeling
    Catastrophe modeling
    Catastrophe modeling is the process of using computer-assisted calculations to estimate the losses that could be sustained due to a catastrophic event such as a hurricane or earthquake...

    .
  • Providing drinking water
    Drinking water
    Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...

    .
  • Designing dams
    DAMS
    Driot-Arnoux Motorsport is a racing team from France, involved in many areas of motorsports. DAMS was founded in 1988 by Jean-Paul Driot and former Formula One driver René Arnoux. It is headquartered near Le Mans, only 2 km from the Bugatti Circuit.- History :The year after its foundation,...

     for water supply
    Water supply
    Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...

     or hydroelectric power
    Hydroelectricity
    Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...

     generation.
  • Designing bridge
    Bridge
    A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...

    s.
  • Designing sewers
    Sanitary sewer
    A sanitary sewer is a separate underground carriage system specifically for transporting sewage from houses and commercial buildings to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater...

     and urban drainage system.
  • Analyzing the impacts of antecedent moisture
    Antecedent moisture
    Antecedent moisture is a term from the fields of Hydrology and sewage collection and disposal that describes the relative wetness or dryness of a watershed or sanitary sewershed. Antecedent moisture conditions change continuously and can have a very significant effect on the flow responses in...

     on sanitary sewer systems.
  • Predicting geomorphological
    Geomorphology
    Geomorphology is the scientific study of landforms and the processes that shape them...

     changes, such as erosion
    Erosion
    Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

     or sedimentation
    Sedimentation
    Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...

    .
  • Assessing the impacts of natural and anthropogenic environmental change on water resources
    Water resources
    Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water....

    .
  • Assessing contaminant
    Pollution
    Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...

     transport risk and establishing environmental policy guidelines.

Hydrologic measurements


Measurement is fundamental for assessing water resources and understanding the processes involved in the hydrologic cycle. Because the hydrologic cycle is so diverse, hydrologic measurement methods span many disciplines: including soils, oceanography, atmospheric science, geology, geophysics and limnology, to name a few. Here, hydrologic measurement methods are organized by hydrologic sub-disciplines. Each of these subdisciplines is addressed briefly with a practical discussion of the methods used to date and a bibliography of background information.

Quantifying groundwater flow and transport
  • Aquifer characterization
    • Flow direction
      • Piezometer
        Piezometer
        A piezometer is either a device used to measure static liquid pressure in a system by measuring the height to which a column of the liquid rises against gravity, or a device which measures the pressure of groundwater at a specific point...

         - groundwater pressure and, by inference, groundwater depth (see: aquifer test
        Aquifer test
        An aquifer test is conducted to evaluate an aquifer by "stimulating" the aquifer through constant pumping, and observing the aquifer's "response" in observation wells...

        )
      • Conductivity, storativity, transmisivity
      • Geophysical methods

  • Vadose zone characterization
    • Infiltration
      • Infiltrometer
        Infiltrometer
        Infiltrometer is a device used to measure the rate of water infiltration into soil or other porous media. Commonly used infiltrometers are single ring or double ring infiltrometer, and also disc permeameter....

         - infiltration
    • Soil moisture
      • Capacitance probe
        Capacitance probe
        Capacitance sensors use capacitance to measure the dielectric permittivity of a surrounding medium.The configuration is like the neutron probe where an access tube made of PVC is installed in the soil. The probe consists of sensing head at fixed depth...

        -soil moisture
      • Time domain reflectometer - soil moisture
      • Tensiometer
        Tensiometer (soil science)
        A Tensiometer in soil science is an instrument used to determine the matric water potential in the vadose zone.-References:* Rawls, W.J., Ahuja, L.R., Brakensiek, D.L., and Shirmohammadi, A. 1993...

         - soil moisture
      • Solute sampling
      • Geophysical methods


Quantifying surface water flow and transport
  • Direct and indirect discharge measurements
    • Stream gauge
      Stream gauge
      A stream gauge, stream gage or gauging station is a location used by hydrologists or environmental scientists to monitor and test terrestrial bodies of water. Hydrometric measurements of water surface elevation and/or volumetric discharge are generally taken and observations of biota may also be...

       - stream flow (see: discharge (hydrology)
      Discharge (hydrology)
      In hydrology, discharge is the volume rate of water flow, including any suspended solids , dissolved chemical species and/or biologic material , which is transported through a given cross-sectional area...

      )
    • Tracer techniques
    • Chemical transport
    • Sediment transport and erosion
    • Stream-aquifer exchange


Quantifying exchanges at the land-atmosphere boundary
  • Precipitation
    • Bulk rain events
      • Disdrometer
        Disdrometer
        A disdrometer is an instrument used to measure the drop size distribution and velocity of falling hydrometeors. Some disdrometers can distinguish between rain, graupel, and hail....

         - precipitation characteristics
      • Radar
        Radar
        Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

         - cloud properties, rain rate estimation, hail and snow detection
      • Rain gauge
        Rain gauge
        A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a set period of time....

         - rain and snowfall
      • Satellite
        Satellite
        In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

         - rainy area identification, rain rate estimation, land-cover/land-use, soil moisture
      • Sling psychrometer - humidity
    • Snow, hail and ice
    • Dew, mist and fog
  • Evaporation
    • from water surfaces
    • Evaporation
      Evaporation
      Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....

       -Symon's evaporation pan
    • from plant surfaces
    • through the boundary layer
  • Transpiration
    • Natural ecosystems
    • Agronomic ecosystems
  • Momentum
  • Heat flux
    • Energy budgets


Uncertainty analyses

Remote sensing of hydrologic processes
  • Land based sensors
  • Airborne Sensors
  • Satellite sensors
    Earth observation satellite
    Earth observation satellites are satellites specifically designed to observe Earth from orbit, similar to reconnaissance satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc....



Water quality
  • Sample collection
  • In-situ methods
  • Physical measurements (includes sediment concentration)
  • Collection of samples to quantify Organic Compounds
  • Collection of samples to quantify Inorganic Compounds
  • Analysis of aqueous Organic Compounds
  • Analysis of aqueous Inorganic Compounds
  • Microbiological sampling and analysis


Integrating measurement and modeling
  • Budget analyses
  • Parameter estimation
  • Scaling in time and space
  • Data assimilation
    Data assimilation
    Applications of data assimilation arise in many fields of geosciences, perhaps most importantly in weather forecasting and hydrology. Data assimilation proceeds by analysis cycles...

  • Quality control of data — see for example Double mass analysis
    Double mass analysis
    Double mass analysis is a commonly used data analysis approach for investigating the behaviour of records made of hydrological or meteorological data at a number of locations. It is used to determine whether there is a need for corrections to the data to account for changes in data collection...


Hydrological prediction


Observations of hydrologic processes are used to make predictions of the future behaviour of hydrologic systems (water flow, water quality). One of the major current concerns in hydrologic research is "Prediction in Ungauged Basins" (PUB), i.e. in basins where no or only very few data exist.

Statistical hydrology


By analysing the statistical
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....

 properties of hydrologic records, such as rainfall or river flow, hydrologists can estimate future hydrologic phenomena, assuming the characteristics of the processes remain unchanged. When making assessments of how often relatively rare events will occur, analyses are made in terms of the return period
Return period
A return period also known as a recurrence interval is an estimate of the interval of time between events like an earthquake, flood or river discharge flow of a certain intensity or size. It is a statistical measurement denoting the average recurrence interval over an extended period of time, and...

 of such events. Other quantities of interest include the average flow in a river, in a year or by season.

These estimates are important for engineers and economists so that proper risk analysis
Risk analysis (Business)
Risk analysis is a technique to identify and assess factors that may jeopardize the success of a project or achieving a goal.This technique also helps to define preventive measures to reduce the probability of these factors from occurring and identify countermeasures to successfully deal with these...

 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
Industry
Industry refers to the production of an economic good or service within an economy.-Industrial sectors:There are four key industrial economic sectors: the primary sector, largely raw material extraction industries such as mining and farming; the secondary sector, involving refining, construction,...

 and residential demands.

Hydrological modeling


Hydrological models are simplified, conceptual representations of a part of the hydrologic cycle. They are primarily used for hydrological prediction and for understanding hydrological processes. Two major types of hydrological 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
    Surface runoff
    Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

    ). Commonly used techniques are regression
    Regression analysis
    In statistics, regression analysis includes many techniques for modeling and analyzing several variables, when the focus is on the relationship between a dependent variable and one or more independent variables...

    , transfer function
    Transfer function
    A transfer function is a mathematical representation, in terms of spatial or temporal frequency, of the relation between the input and output of a linear time-invariant system. With optical imaging devices, for example, it is the Fourier transform of the point spread function i.e...

    s, and system identification
    System identification
    In control engineering, the field of system identification uses statistical methods to build mathematical models of dynamical systems from measured data...

    . The simplest of these models may be linear models, but it is common to deploy non-linear components to represent some general aspects of a catchment's response without going deeply into the real physical processes involved. An example of such an aspect is the well-known behaviour that a catchment will respond much more quickly and strongly when it is already wet than when it is dry..

  • 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
    Surface runoff
    Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

    , subsurface flow
    Subsurface flow
    Subsurface flow, in hydrology, is the flow of water beneath earth's surface as part of the water cycle.In the water cycle, when precipitation falls on the earth's land, some of the water flows on the surface forming streams and rivers...

    , evapotranspiration
    Evapotranspiration
    Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...

    , and channel flow
    Open channel flow
    Open-Channel Flow, a branch of Hydraulics, is a type of liquid flow within a conduit with a free surface, known as a channel. The other type of flow within a conduit is pipe flow. These two types of flow are similar in many ways, but differ in one important respect; the free surface...

    , 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.


Recent research in hydrological modeling tries to have a more global approach to the understanding of the behaviour of hydrologic systems
Behavioral modeling in hydrology
In hydrology, behavioral modeling is a modeling approach that focuses on the modeling of the behavior of hydrological systems.The behavioral modeling approach makes the main assumption that every system, given its environment, has a most probable behavior...

 to make better predictions and to face the major challenges in water resources management.

Hydrologic transport



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
Point source (pollution)
A point source of pollution is a single identifiable localized source of air, water, thermal, noise or light pollution. A point source has negligible extent, distinguishing it from other pollution source geometries. The sources are called point sources because in mathematical modeling, they can be...

 discharge or a line source
Line source
A line source is a source of air, noise, water contamination or electromagnetic radiation that emanates from a linear geometry...

 or area source
Area source (pollution)
Area sources are sources of pollution which emit a substance or radiation from a specified area.-Air pollution:For example, area sources of air pollution are air pollutant emission sources which operate within a certain locale. The U.S. Environmental Protection Agency has categorized 70 different...

, such as surface runoff
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...

. Since the 1960s rather complex mathematical model
Mathematical model
A mathematical model is a description of a system using mathematical concepts and language. The process of developing a mathematical model is termed mathematical modeling. Mathematical models are used not only in the natural sciences and engineering disciplines A mathematical model is a...

s have been developed, facilitated by the availability of high speed computers. The most common pollutant classes analyzed are nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s, pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

s, total dissolved solids
Total dissolved solids
Total Dissolved Solids is a measure of the combined content of all inorganic and organic substances contained in a liquid in: molecular, ionized or micro-granular suspended form. Generally the operational definition is that the solids must be small enough to survive filtration through a sieve...

 and sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

.

See also

  • Aquatic chemistry
  • Civil engineering
    Civil engineering
    Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...

  • Climatology
    Climatology
    Climatology is the study of climate, scientifically defined as weather conditions averaged over a period of time, and is a branch of the atmospheric sciences...

  • Environmental engineering
    Environmental engineering
    Environmental engineering is the application of science and engineering principles to improve the natural environment , to provide healthy water, air, and land for human habitation and for other organisms, and to remediate polluted sites...

  • Environmental engineering science
    Environmental Engineering Science
    Environmental engineering science is a multidisciplinary field of engineering science that combines the biological, chemical and physical sciences with the field of engineering...

  • Geomorphology
    Geomorphology
    Geomorphology is the scientific study of landforms and the processes that shape them...

  • Hydrography
    Hydrography
    Hydrography is the measurement of the depths, the tides and currents of a body of water and establishment of the sea, river or lake bed topography and morphology. Normally and historically for the purpose of charting a body of water for the safe navigation of shipping...

  • Hydraulic engineering
    Hydraulic engineering
    This article is about civil engineering. For the mechanical engineering discipline see Hydraulic machineryHydraulic engineering as a sub-discipline of civil engineering is concerned with the flow and conveyance of fluids, principally water and sewage. One feature of these systems is the extensive...

    , a sub-discipline of civil engineering concerned with the flow and conveyance of fluids, principally water
  • Physical geography
    Physical geography
    Physical geography is one of the two major subfields of geography. Physical geography is that branch of natural science which deals with the study of processes and patterns in the natural environment like the atmosphere, biosphere and geosphere, as opposed to the cultural or built environment, the...

  • Hydropower
    Hydropower
    Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...

  • International Hydrological Programme
    International Hydrological Programme
    The International Hydrological Programme is a scientific programme of UNESCO that focuses on the use and availability of water.- On-line resources :*...

  • Hydrology (agriculture)
    Hydrology (agriculture)
    Agricultural hydrology is the study of water balance components intervening in agricultural water management, notably in irrigation and drainage.-Water balance components:...

  • Water distribution on Earth
    Water distribution on Earth
    Water is widely distributed on Earth as freshwater and salt water in the oceans. The Earth is often referred to as the "blue planet" because when viewed from space it appears blue...

  • Nash–Sutcliffe model efficiency coefficient
  • WEAP
    WEAP
    WEAP: the Water Evaluation And Planning system is a Windows-based decision support system for integrated water resources management and policy analysis...

     (Water Evaluation And Planning) software to model catchment hydrology from climate and land use data

Further reading

  • Introduction to Physical Hydrology, Martin Hendriks 2010. ISBN 9780199296842
  • 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
  • Hydrologic Analysis and Design. McCuen, Third Edition, 2005. ISBN 0-13-142424-6
  • Hydrological Processes, ISSN: 1099-1085 (electronic) 0885-6087 (paper), John Wiley & Sons
    John Wiley & Sons
    John Wiley & Sons, Inc., also referred to as Wiley, is a global publishing company that specializes in academic publishing and markets its products to professionals and consumers, students and instructors in higher education, and researchers and practitioners in scientific, technical, medical, and...

  • Journal of Hydroinformatics, ISSN: 1464-7141, IWA Publishing
  • Hydrology Research (formerly Nordic Hydrology), ISSN: 0029-1277, IWA Publishing
  • Journal of Hydrologic Engineering
    Journal of Hydrologic Engineering
    The Journal of Hydrologic Engineering is a monthly engineering journal, that was first published by the American Society of Civil Engineers in 1996 . The journal provides information on the development of new hydrologic methods, theories, and applications to current engineering problems...

    , ISSN: 0733-9496, ASCE
    American Society of Civil Engineers
    The American Society of Civil Engineers is a professional body founded in 1852 to represent members of the civil engineering profession worldwide. It is the oldest national engineering society in the United States. ASCE's vision is to have engineers positioned as global leaders who strive toward...

    Publication

Other on-line resources


National and international research bodies


National and international societies


Basin- and catchment-wide overviews