Piscina and Castella

On basins and control mechanisms in Roman aqueducts, Part 2

Illustrations to Appendices II: Settling versus Storage basins

Settling basin Storage basin
A. Supply almos equal to discharge
Major elements:
  • In the flow
  • (Almost) permanent in use (except during maintenance)
  • one inlet (I), one exit (E)
  • Overflow (O) is optional
  • Drain (D) is necessary (although there are other ways of cleaning) for discharge of debris and imputities
  • Acces for control and cleaning
  • By-pass os optional )*
Major elements:
  • Near the flow
  • In use on demand
  • Control mechanisms at inlet (O) and exit (E) to control the supply and the discharge
  • Overflow (O) necessary for security reasons
  • Drain (D) and access recommended (also in storage basins there is sedimentation)
  • Loss of head (for a medium size reservoir (10 x 5 x 3) almost 3 meters !!
B. Supply < discharge
C. Supply > discharge
An overflow or by-pass mechanism has to do its work The overflow mechanism will do its work
)* For a settling basin a by-pass mechanism is optional; for a storage basin a by-pass is problematic because of the gradient / loss of head