Hydrology
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, watershed 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
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. 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.
Sub-fields 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 movement of water between land and water body surfaces and the lower atmosphere.
Isotope hydrology is the study of the istopic 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
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
- 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.
See: return period.
Hydrologic Modeling
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.
Hydrologic Transport
Water movement is a significant means by which other material, such as soil or pollutants, are transported from place to place.
See: erosion, pollution.
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.