Runoff
The water that reaches streams from precipitation and snowmelt — the annual supply a basin actually produces.
Runoff is what is left after evaporation, sublimation, soil absorption and plant uptake take their share, and those losses vary with temperature and soil moisture. A warm spring can convert a healthy snowpack into a disappointing runoff season.
Forecast runoff, not snowpack alone, is what water managers allocate against. The gap between the two is why a basin at normal SWE can still deliver a short year.
Where this shows up in the data
See also
More in Hydrology & supply
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