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study of water and its properties, including its distribution and movement in and through the land areas of the earth. The hydrologic cycle consists of the passage of water from the oceans into the atmosphere by evaporation and transpiration (or evapotranspiration), onto the lands, over and under the lands as runoff and infiltration, and back to the oceans. Hydrology is principally concerned with the part of the cycle after the precipitation of water onto the land and before its return to the oceans; thus meteorologymeteorology,
branch of science that deals with the atmosphere of a planet, particularly that of the earth, the most important application of which is the analysis and prediction of weather.
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 and oceanographyoceanography,
study of the seas and oceans. The major divisions of oceanography include the geological study of the ocean floor (see plate tectonics) and features; physical oceanography, which is concerned with the physical attributes of the ocean water, such as currents and
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 are closely related to hydrology. Hydrologists study the cycle by measuring such variables as the amount and intensity of precipitation, the amount of water stored as snow or in glaciers, the advance and retreat of glaciers, the rate of flow in streams, and the soil-water balance. Hydrology also includes the study of the amount and flow of groundwater. Though the flow of water cannot be seen under the surface, hydrologists can deduce the flow by understanding the characteristics, including permeability, of the soil and bedrock; how water behaves near other sources of water, such as rivers and oceans; and fluid flow models based on water movements on the earth's surface. Hydrology is also important to the study of water pollution, especially of groundwater and other potable water supplies. Knowledge of hydrology is extensively used to determine the movement and extent of contamination from landfills, mine runoff, and other potentially contaminated sites to surface and subsurface water. See water supplywater supply,
process or activity by which water is provided for some use, e.g., to a home, factory, or business. The term may also refer to the supply of water provided in this way.
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The science of water relating to the occurrence, properties, distribution, circulation, and transport of water.



the science that studies natural waters and the phenomena and processes occurring in them. As a geophysical science, hydrology is in close contact with the sciences of geographic, geologic, and biological cycles.

The subject matter of hydrology is bodies of water—that is, oceans, seas, rivers, lakes, reservoirs, swamps, and accumulations of moisture in the form of snow cover, glaciers, and soil and subterranean waters. The main problems of present-day hydrology are to investigate the hydrologic cycle and the influence on it of human activity, as well as the control of the regimen of bodies of water and the stream-flow regimen of territories; to perform space-time analyses of hydrologic elements (water level, discharge, temperature, and so on) for individual territories and the earth as a whole; and to discover patterns in the variations of these elements. The principal practical application of hydrology is in the evaluation of the present state of water resources, in forecasting their future state, and in laying the basis for their rational utilization.

Based on the specific characteristics of bodies of water and of the methods of their study, hydrology is divided into oceanography (hydrology of the sea), land hydrology (hydrology proper; more precisely, hydrology of the surface water of land), and hydrogeology (hydrology of subterranean water).

Hydrology initially developed as a branch of physical geography, hydraulic engineering, geology, and navigation and took shape as a system of scientific knowledge only at the beginning of the 20th century. A definition of hydrology as a science was provided by V. G. Glushkov in 1915. A large role in the formation of hydrology was played by the establishment in 1919 of the State Hydrologic Institute. Present-day hydrology makes wide use of methods employed in geography, physics, and other sciences, and the role of mathematical methodology is steadily increasing.


Glushkov, V. G. Voprosy teorii i melody gidrologic he skikh issledovanii. Moscow, 1961.
Kalinin, G. P. Problemy global’noi gidrologii. Leningrad, 1968.
Sokolov, A. A., and A. I. Chebotarev. Ocherki razvitiia gidrologii v SSSR. Leningrad, 1970.
Chebotarev, A. I. Obshchaia gidrologiia (vody sushi). Leningrad, 1960.



the study of the distribution, conservation, use, etc., of the water of the earth and its atmosphere, particularly at the land surface
References in periodicals archive ?
Coastal systems are hydrologically complex and are among the most susceptible to direct disturbance through global climate change.
Sediment chemistry and nutrient influx in a hydrologically restored bottomland hardwood forest in Midwestern USA.
461) However, the lower court followed the Mono Lake precedent to conclude that diverting essential hydrologically connected groundwater tributaries is analogous to diverting essential non-navigable tributaries, opening the possibility that groundwater resources may also be subject to public trust protection.
Diamonds, pyrope garnet and ilmenite were identified along this stretch of river which is hydrologically and geographically distinct from the river systems containing alluvial diamonds and diamondiferous kimberlite sources in areas to the east.
And, hopefully most of the hydrologically restored active bogs will revert to being carbon sinks.
2] and consists of 143 shallow lakes and 800ha of Phragmites australis marshes, which are hydrologically linked together by >3700 ditches and fiver courses (Xu 2004).
The federal government argues permits were needed because the wetlands are adjacent to, are hydrologically connected with and are part of headwater systems that provide valuable habitat for wildlife and ensure the health of larger navigable downstream waters.
The flow for this stream is hydrologically controlled at Alum Creek Reservoir.
Because of the geomorphic setting, this cluster of wetlands can be viewed as a unit hydrologically as well as biologically with a need to preserve various types and sizes of wetlands for the diverse functions of many species of mobile birds.
Overall, leaf litterfall was 38% lower on plots with mean growing-season water depths above the soil surface, and reductions in NPP were much greater (fivefold) in hydrologically altered sites.
Other western states have integrated their hydrologically connected groundwater and surface water in other ways, not all equally successfully.
Cover of 50% is likely to reduce peak runoff rates by 4mm/h; while statistically significant, is not of great practical impact hydrologically, but may influence erosion via overland flow velocity.