Hydrology
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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 environmental science, 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 not only in that it allows us to better understand the world in which we live, but also by providing 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
- Aquatic chemistry
- Civil engineering
- Climatology
- Environmental engineering
- Geomorphology
- Hydraulic engineering
- Limnology
- Oceanography
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 dicisions 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 and neural networks. 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
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;
- 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
- Introduction to Hydrology, 4e. Viessman and Lewis, 1996. ISBN 0-673-99337-X
- Handbook of Hydrology. ISBN 0070397325
- 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]
| 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 |
| Environmental technology |
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