Units#

The plugin uses the same sets of units as Epanet, including both SI-based units and US customary units. Some units also depend on the equation used. For reference, Table 1 includes unit conversions.

Note

Within the WNTR python module all units are in pure SI. This plugin automatically translates units to and from SI when reading and writing QGIS Layers.

Table 1 EPANET INP File Unit Conventions#

Parameter

US customary units

SI-based units

Concentration

mass /L where mass can be defined as mg or ug

mass /L where mass can be defined as mg or ug

Demand

Same as flow

Same as flow

Diameter (Pipes)

in

mm

Diameter (Tanks)

ft

m

Efficiency (Pumps)

percent

percent

Elevation

ft

m

Emitter coefficient

flow / sqrt(psi)

flow / sqrt(m)

Energy

kW-hours

kW-hours

Flow

  • CFS: ft 3 /s

  • GPM: gal/min

  • MGD: million gal/day

  • IMGD: million imperial gal/day

  • AFD: acre-feet/day

  • LPS: L/s

  • LPM: L/min

  • MLD: million L/day

  • CMH: m 3 /hr

  • CMD: m 3 /day

Friction factor

unitless

unitless

Hydraulic head

ft

m

Length

ft

m

Minor loss coefficient

unitless

unitless

Power

horsepower

kW

Pressure

psi

m

Reaction coefficient (Bulk)

1/day (1st-order)

1/day (1st-order)

Reaction coefficient (Wall)

  • mass /ft/day (0-order)

  • ft/day (1st-order)

  • mass /m/day (0-order)

  • m/day (1st-order)

Roughness coefficient

  • 0.001 ft (Darcy-Weisbach)

  • unitless (otherwise)

  • mm (Darcy-Weisbach)

  • unitless (otherwise)

Source mass injection rate

mass /min

mass /min

Velocity

ft/s

m/s

Volume

ft 3

m 3

Water age

hours

hours

WNTR works using pure SI units, and it is also possible to select ‘SI’ as a unit set. This will use the following units:

  • Acceleration = \(\rm g\) (\(\rm g \equiv 9.80665 m/s^2\))

  • Concentration = \(\rm kg/m^3\)

  • Demand = \(\rm m^3/s\)

  • Diameter = \(\rm m\)

  • Elevation = \(\rm m\)

  • Energy = \(\rm J\)

  • Flow rate = \(\rm m^3/s\)

  • Head = \(\rm m\)

  • Headloss = \(\rm m\)

  • Length = \(\rm m\)

  • Mass = \(\rm kg\)

  • Mass injection = \(\rm kg/s\)

  • Power = \(\rm W\)

  • Pressure head = \(\rm m\) (assumes a fluid density of 1000 \(\rm kg/m^3\))

  • Time = \(\rm s\)

  • Velocity = \(\rm m/s\)

  • Volume = \(\rm m^3\)

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