Groundwater flow - ie that water that seeps through
the ground into water courses.
E =
Evaporation - direct evaporation back into the air
T =
Transpiration - The uptake of water by plants and
subsequent loss to the air as water vapour through the leaves
S =
Storage - That water that is held in the soils etc.
Without loss to water courses or ground water. E.g. in areas of
peat, the peat holds a certain amount of water like a sponge