Lesson 2 - Water Budget Equation

Catchment Area

the area of land draining into a stream or water course at a given location

Drainage Area/Drainage Basin

What is the catchment area also called?

mass inflow - mass outflow = change in mass storage

For a given problem area (a catchment) in an interval of time, how is the continuity equation of water written as?

average depths over the catchment area

In hydrologic calculations, the volumes are often expressed as _____.

P - R - G - E - T = delta S

• P - precipitation

• R - surface runoff

• G - net groundwater flow out of the catchment

• E - evaporation

• T - transpiration

• delta S - change in storage

How do you write an expression for the water budget of a catchment for a time interval?

• S_s - surface water storage

• S_m - water in storage as soil moisture

• S_g - water in storage as groundwater

S = S_s + S_m + S_g

Three Components of Storage (S):

R = P - L

How can the rainfall-runoff relationship be presented?

Losses

water not available to runoff due to infiltration, evaporation, transpiration and surface storage