How much water you'd get if you melted all the snow on the ground. A deep, fluffy snowpack and a shallow, dense one can hold the same amount of water, so SWE measures the water, not just the depth.

Snow water equivalent (SWE)

How much water you’d get if you melted all the snow on the ground. A deep, fluffy snowpack and a shallow, dense one can hold the same amount of water, so SWE measures the water, not just the depth.

Why it matters

Mountain snowpack is a frozen reservoir that feeds rivers, reservoirs, and farms when it melts, so SWE forecasts water supply and flood risk for billions of people downstream.

Where you’ll meet it

AMSR2 passive microwave estimates snow water equivalent over large regions.
MODIS and VIIRS map snow cover extent that complements SWE estimates.
NASA’s SnowEx field campaigns test new ways to measure SWE from the air and space.

In plain terms

It’s like asking not how tall the snowdrift is, but how full a bucket it would fill if it melted — because that water is what matters come spring.