Glossary/water dictionary

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hardness

A water-quality indication of the concentration of alkaline salts in water, mainly calcium and magnesium. If the water you use is 'hard', then more soap, detergent or shampoo is necessary to raise a lather.^

headwater

(1) The source and upper reaches of a stream; also the upper reaches of a reservoir. (2) The water upstream from a structure or point on a stream. (3) The small streams that come together to form a river. Also may be thought of as any and all parts of a river basin except the mainstream river and main tributaries.^

hydroelectric power water use

The use of water in the generation of electricity at plants where the turbine generators are driven by falling water.^

hydrologic cycle

The circulation of water from the sea through the atmosphere to the land and then, often with many delays, back to the sea or ocean. The water passes through various stages and processes, such as precipitation, interception, runoff, infiltration, percolation, groundwater storage, evaporation and transpiration; also the many shortcuts of the water that is returned to the atmosphere without reaching the sea.^

hydrologic cycle

The cyclic transfer of water vapor from the Earth's surface via evapotranspiration into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into the oceans.^

hydrologic studies

Collection of hydrological data and appraisal of available water supply for various phases of water resources development, and appurtenant works and operations related thereto, including the determination of the extremes, such as floods and droughts. It includes methods and techniques for installing and using hydro-meteorological observation stations.^