GPS-X Technical Reference

Influent Models 66
RUNOFF MODEL
The flow is specified via one of the five methods:
1. Data – users set the flow rate directly, via menu entry or read from file.
2. Sinusoidal – GPS-X applies a sinusoidal curve to the influent flow set in the
menu or read from file.
3. Diurnal Flow – a daily diurnal patter is set via flow rates at different times
of the day.
4. Diurnal Flow Factor – a daily diurnal pattern is set via flow rates at
different times of the day.
5. Runoff – an empirical, stochastic model is used to generate flow patterns
based on storm runoff
The runoff flow model uses a parallel linear reservoir model to simulate wet weather flow in
sanitary and combined sewer systems. This model is not a mechanistic hydrological model, but a
simple mathematical transformation.
The equations are:
Equation 5.1
and
Equation 5.2
where:
P d
P i
P total
C d
C i
= rainfall that enters the sewer system directly
= rainfall that enters the sewer system indirectly
= total rainfall over the catchment area
= fraction of total rainfall that enters the sewer system directly
= fraction of total rainfall that enters the sewer system indirectly
GPS-X Technical Reference