Water Budget Methods
�Basic relationship: (assuming no change in water level)
�   runoff + direct inflow + precipitation = evaporation + outflow
Text Box: Runoff
Inflow
Outflow
Precipitation
Evaporation
From an annual perspective, the water level of a lake is in equilibrium, meaning that the water addition (through runoff, direct inflow, and precipitation) is equal to the water lost (through evaporation and outflow). These volumes of water are calculated by multiplying the land area they refer to by specific coefficients.
Determining the outflow is the ultimate goal as it relates directly to the flushing rate.