Catchment hydrology

Water balance

Catchment hydrology is based on the principal of continuity, which is used to perform a water balance on a catchment:

I − O = d S / d t ,

where I = inputs (P, precipitation + OW, occult water), O = outputs (ET, evapotranspiration + R, runoff), and d S / d t = the change in catchment storage over time.

Neglecting the minor inputs of occult water, the water balance can be revised to

P − R − E T = d S / d t .

Finally, considering a catchment on a long time scale, typically a year or more, removes the storage component from the equation:

P − R = E T .

(For more information see water balance)

Terminology

There are many terms involved with and related to catchment hydrology. These basic ones are taken from the glossary of terms in Kendall and McDonnell, 1998: