Free of water under dry weather flow conditions.

Pollution arising from land-use activities (urban and rural) that are dispersed across a catchment, or sub-catchment, and do not arise as a process effluent, municipal sewage effluent, or an effluent discharge from farm buildings.

All flow within a drainage system excepting that caused directly by rainfall.

A collection of pipes, channels and other engineering works designed to convey stormwater way from a built up environment.

A pipeline, usually underground, designed to carry wastewater, and/or surface water from a source to a sewer, a pipeline carrying land drainage flows or surface water from a highway.

A coefficient, derived by experiment, applied in a formula, by which the theoretical discharge of a fluid through an oriface, weir or nozzle, can be correctly calculated.

The volume of liquid flowing through a cross-section of conduit per unit of time.

Tanks constructed in a sewerage system to store a volume of water temporarily during peak flows (see off-line and on-line tanks).

A vegetated depression which is normally dry, excepting post storm events, constructed to store water temporarily to attenuate flows. May allow infiltration of water in to the ground.