Water balance (per unit area) of a river basin and the air column above it


Storage terms Unit [kg / m^2] or [mm] (assuming density of liquid water)
Water vapor storage ("precipitable water")
Terrestrial water Storage (surface water+snow+soil moisture+groundwater)
Flux terms [kg /(m^2 s)] or [mm / s] (usually [mm/day], [mm/year] etc.)
Convergence of horizontal moisture transport;  Precipitation;
E:vaporation;  Runoff (in ocean, net divergence of freshwater transport)