Depletion of snow and ice by melting and evaporation.

The part of a valley or canyon wall against which a dam is constructed. Right and left abutments are those on respective sides of an observer looking downstream.

Reservoir water that moves through seams or pores in the natural abutment material and exits as seepage.

Reservoir water that moves through seams or pores in the natural abutment material and exits as seepage.

An acronym for Altocumulus Castellanus.

A cloud which is dependent on a larger cloud system for development and continuance. Roll clouds, shelf clouds, and wall clouds are examples of accessory clouds.

Degree of conformity of a measure to a standard or true value.

Cloud or rain droplets containing pollutants, such as oxides of sulfur and nitrogen, to make them acidic.

Cloud or rain droplets containing pollutants, such as oxides of sulfur and nitrogen, to make them acidic.

The amount of water required to cover one acre to a depth of one foot. An acre-foot equals 326,851 gallons, or 43,560 cubic feet.