Definition
The depth of liquid water that would result if a sample of snow, ice, or other frozen precipitation were completely melted. Used in meteorology to express the actual moisture content of frozen precipitation, since a given depth of snow contains far less water than the same depth of rain.
Plain English
How much rain you would have if all the snow or ice on the ground melted into water. A foot of snow does not become a foot of water — it usually melts down to about an inch.
Context Anchor
Seen in weather reports, forecasts, and winter operations discussions when snow or ice amount is being described by how much water it contains.
Derivation
Equivalent comes from Latin roots meaning “equal in value.” In this term, the frozen amount is being expressed as the equal amount of liquid water it would become if melted.
Why Pilots Care
Determines snow weight on wings and runways, influences de-icing needs, and affects braking and takeoff performance calculations.
Analogy
A bowl of fluffy snow may look deep, but after it melts it may make only a small amount of water. Water equivalent is the melted amount, not the fluffy depth.
Grounding Statement
Water equivalent turns snow or ice into one simple question: how much liquid water would this become if it melted?
Intuition Check
Water equivalent does not mean the visible depth of the snow or ice. It means the liquid-water depth after that frozen material is melted.
Example Sentence 1
The overnight snowfall measured six inches, with a water equivalent of about half an inch.
Example Sentence 2
With a 12-to-1 water equivalent ratio the dry snow remained light but still required a longer takeoff roll.