Water balance

The water balance portrays the hydrological cycle quantitatively:

The general water balance equation is:

P - R - G - E - T = DS

where:

P precipitation [unit of heigt] or [unit of volume/unit of time]
R

runoff, [unit of height] or [unit of volume/unit of time]
R = Rout - Rin
Rout = runoff as outflow from the water body/hydrologic regin
Rin = runoff as inlfux into the water body/hydrologic region 

G

groundwater flow, [unit of height] of [unit of volume/unit of time]
G = Gout - Gin
Gout = groundwater as outflow from the water body/hydrologic region
Gin = groundwater as influx into the water body/hydrologic region

E evaporation, [unit of height] or [unit of volume/unit of time]
T  transpiration, [unit of height] or [unit of volume/unit of time]
DS  change in storage, [unit of height] or [unit of volume/unit of time]