Valleys typically eroded by stream action. U-Shaped Valleys - by contrast - are characteristic of glacial erosion.

Removal of liquid material from a solution or mixture under reduced air pressure - which results in drying at a lower temperature than is required at full pressure.

(Water Quality) A process by which liquid is extracted from a sludge. The filtrate is forced through a filtering material by means of a vacuum.

Of - relating to - or being water that is located in the Zone of Aeration in the earth

Water occurring in the Unsaturated Zone (Vadose Zone) between the land surface and the water table.

The subsurface zone between the water table (Zone of Saturation) and the land surface where some of the spaces between the soil particles are filled with air. Also referred to as the Unsaturated Zone or - less frequently - the Zone of Aeration.

A valley - often coursed by a stream; a dale.

(1) An area of land that is lower than the land on either side of it. (2) An elongated depression cut by stream erosion and associated water erosion on its sideslopes (stream valley). Also used in the vernacular for Intermontane and Intramontane Basins. Also see U-Shaped Valleys and V-Shaped Valleys.

Alluvium or other material occupying areas below mountain slopes.

A device fitted to a pipeline or orifice in which the closure member is either rotated or moved transversely or longitudinally in the waterway so as to control or stop the flow.

The gaseous state of a substance which under ordinary conditions exists as a liquid or solid.

A continuous plastic membrane which surrounds the entire thermal envelope of a house and prevents moisture penetration into the wall cavity. Also referred to as a Vapor Retarder.

The layer of air which overlies a body of water and - due to its proximity to the water - has a water vapor content higher than that of the surrounding atmosphere.

The gaseous flow of water vapor in soils from a moist or warm zone of higher potential to a drier or colder zone of lower potential.

Flue gases visible because they contain water droplets.