Warning
Dissemination of message signalling imminent hazard which may include advice on protective measures. See also "alert".

Water management system (also water system)
Group of water engineering structures and related water bodies serving one or more purposes and managed as a unified whole.

Water management policy
Collection of legislation, legal interpretations, governmental decisions, agency rules and regulations, and cultural responses by which a country's actions concerning the quantity and quality of water are guided. (H)

Watershed
All land within the confines of a drainage divide. This is also called a "catchment " or "drainage basin". All surface water has a common outlet.

Watershed divide (syn. drainage divide)
Boundary line separating adjacent drainage basins.

Weathering
The break up and/or transformation of rocks by mechanical, chemical and biological processes, mainly under the influence of the atmosphere.

Windbreak
A barrier used to decrease the wind speed.

Wind force
Number on a Beaufort scale corresponding to the effects produced by winds within a range of speeds.

Wind pressure (Wind load)
The total force exerted upon a structure by wind. For flat surface it is the sum of the dynamic pressure exerted on the windward side and the pressure decrease, or suction, produced on the sheltered side (M)

World Weather Watch (WWW)
The world-wide, co-ordinated, developing system of meteorological facilities and services provided by WMO Members for the purpose of ensuring that all Members obtain the meteorological information required both for operational work and research The essential elements of the WWW are: The Global Observing System, The Global Data-processing System and the Global Telecommunication System (used also for transmission of seismic information in the Far East). (M)

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