- Streamflow can only occur when the water stores in the drainage basin are capable of releasing water, and when there is direct surface runoff.
- In order to understand the streamflow pattern across a year (called the river regime) you have to understand the changing balance of three key variables – evapotranspiration, soil storage and groundwater storage.
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This dynamic relationship can be expressed as the water balance equation:
Precipitation (P) = streamflow (Q) + evapotranspiration (E) +/- changes in storage (S)
