Creating and Editing the Model

The model can consist of up to six layers which represent physical parts of the network.

There are three possible node layers:

• Junctions, which are points in the network where links join together and where water enters or leaves the network.

• Reservoirs, which are nodes that represent an infinite external source or sink of water to the network. They are used to model such things as lakes, rivers, groundwater aquifers, and tie-ins to other systems. Reservoirs can also serve as water quality source points.

• Tanks, which are nodes that represent a finite storage of water in the network. They are used to model water storage tanks, elevated tanks, and other types of water storage facilities.

There are also three possible link layers:

• Pipes, are links that convey water from one point in the network to another. EPANET assumes that all pipes are full at all times. Flow direction is from the end at higher hydraulic head (internal energy per weight of water) to that at lower head.

• Valves, which are used to control the flow of water in the network. They can be used to model pressure reducing valves, flow control valves, and other types of valves.

• Pumps, which are links that impart energy to a fluid thereby raising its hydraulic head. The principal input parameters are either it’s pump curve or they can be represented as a constant energy device, one that supplies a constant amount of energy to the fluid for all combinations of flow and head.

Creating Layers

Each of the six types of physical object is represented by a normal layer in QGIS. This can be any filetype: shapefile, geopackage, memory layer, etc. Not all layers need to be present if they are not used.

You can use the ‘new’ button on the toolbar to create a set of layers with default properties.

Alternatively, for more control, you can use the ‘Create Template Layers’ processing tool.

It is also possible to use any layer - you do not have to use the layers created by the plugin. Any layer with the appropriate geometry type (points for nodes and linestrings for links) and with the minimum necessary fields can be used.

Attributes

Attributes are based on the attributes within WNTR. Details of what they represent can be found in the WNTR and / or EPANET documentation.

Some attributes are required - these are marked with an asterisk (*). Others use default values from WNTR if not defined.

Name All layers can optionally use the attribute name to give a name to each item, which will be visible on the output layer. The name must be a string of less than 32 characters and with no spaces. If no name is given, it will be automatically generated.

Patterns All patterns are string fields. This can be left blank. Otherwise, it should be input as a series of numbers seperated by spaces:

1  1.2 1.3 0.8

Patterns will also accept a field of type list, where each item in the list is a number.

Curves Curves should be inputted with the following form, where each pair of numbers in brackets is an x, y point on the curve.

(0, 10), (2, 5), (3.3, 7)

Geographical attributes All geographical (coordinates, vertices) and network-related (start_node_name and end_node_name) WNTR attributes are not used. This is because they are calculated automatically based on the geometry of the features.

Warning

The attributes must have the exact names listed below. However, when they are created by the plugin in QGIS, they will also be given ‘alias’ names, which will be more human-readable versions. These aliases will be most the most visible within the user interface.

The alias names will also be translated if using the plugin in a different language, whilst the underlying attribute names will not be.

The values of attributes may also be given aliases. For example, the valve_type attribute value ‘PRV’ can have the alias ‘Pressure Reducing Valve’. The alias will be used in the user interface, but the underlying value will still be ‘PRV’.

Table 2 Possible Junction Attributes

Attribute	Alias	Type	Value(s)	Used for
name	Name	Text (string)	Will generate automatically if blank
elevation*	Elevation	Decimal (double)
base_demand	Base Demand	Decimal (double)
demand_pattern	Demand Pattern	Text (string) or Decimal list	Pattern
emitter_coefficient	Emitter Coefficient	Decimal (double)
initial_quality	Initial Quality	Decimal (double)		Water Quality Analysis
minimum_pressure	Minimum Pressure	Decimal (double)		Pressure Dependent Demand
required_pressure	Required Pressure	Decimal (double)		Pressure Dependent Demand
pressure_exponent	Pressure Exponent	Decimal (double)		Pressure Dependent Demand

Table 3 Possible Reservoir Attributes

Attribute	Alias	Type	Value(s)	Used for
name	Name	Text (string)	Will generate automatically if blank
base_head*	Base Head	Decimal (double)
head_pattern	Head Pattern	Text (string) or Decimal list	Pattern
initial_quality	Initial Quality	Decimal (double)		Water Quality Analysis

Table 4 Possible Tank Attributes

Attribute	Alias	Type	Value(s)	Used for
name	Name	Text (string)	Will generate automatically if blank
elevation*	Elevation	Decimal (double)
init_level*	Initial Level	Decimal (double)
min_level*	Minimum Level	Decimal (double)
max_level*	Maximum Level	Decimal (double)
diameter*	Diameter	Decimal (double)
min_vol	Minimum Volume	Decimal (double)
vol_curve	Volume Curve	Text (string)	Curve
overflow	Overflow	Boolean
initial_quality	Initial Quality	Decimal (double)		Water Quality Analysis
mixing_model	Mixing Model	Text (string)	MIXED, 2COMP, FIFO, FILO	Water Quality Analysis
mixing_fraction	Mixing Fraction	Decimal (double)		Water Quality Analysis
bulk_coeff	Bulk Coefficient	Decimal (double)		Water Quality Analysis

Table 5 Possible Pipes Attributes

Attribute	Alias	Type	Value(s)	Used for
name	Name	Text (string)	Will generate automatically if blank
length	Length	Decimal (double)	Will calculate if blank
diameter*	Diameter	Decimal (double)
roughness*	Roughness	Decimal (double)
minor_loss	Minor Loss Coefficient	Decimal (double)
initial_status	Initial Status	Text (string)	Open, Closed
check_valve	Check Valve	Boolean
bulk_coeff	Bulk Coefficient	Decimal (double)		Water Quality Analysis
wall_coeff	Wall Coefficient	Decimal (double)		Water Quality Analysis

Table 6 Possible Pumps Attributes

Attribute	Alias	Type	Value(s)	Used for
name	Name	Text (string)	Will generate automatically if blank
pump_type*	Pump Type	Text (string)	POWER, HEAD
pump_curve	Pump Curve	Text (string)	Curve
power	Power	Decimal (double)
base_speed	Base Speed	Decimal (double)
speed_pattern	Speed Pattern	Text (string) or Decimal list	Pattern
initial_status	Initial Status	Text (string)	Open, Closed
efficiency	Efficiency	Text (string)	Curve	Energy
energy_pattern	Energy Pattern	Text (string) or Decimal list	Pattern	Energy
energy_price	Energy Price	Decimal (double)		Energy

Pumps can be of two types: ‘POWER’ or ‘HEAD’. The type of pump is determined by the pump_type attribute. If this attribute is not set, the pump will be treated as a ‘POWER’ pump.

Power pumps must have a power attribute, which is a float representing the power of the pump.

Head pumps must have a pump_curve attribute, which is a string representing the head curve of the pump in the form of a list of points, e.g. (0, 10), (2, 5), (3.3, 7).

Table 7 Possible Valve Attributes

Attribute	Alias	Type	Value(s)	Used for
name	Name	Text (string)	Will generate automatically if blank
diameter*	Diameter	Decimal (double)
valve_type*	Valve Type	Text (string)	PRV, PSV, PBV, FCV, TCV, GPV
minor_loss	Minor Loss Coefficient	Decimal (double)
initial_status	Initial Status	Text (string)	Active, Open, Closed
initial_setting	Initial Setting	Decimal (double)
headloss_curve	Headloss Curve	Text (string)	Curve

All valves must have a valve_type attribute. The options are:

• PRV - Pressure Reducing Valves limit the pressure at a point in the pipe network. They must have an initial_setting attribute which represents that pressure.

• PSV - Pressure Sustaining Valves maintain a set pressure at a specific point in the pipe network. They must have an initial_setting attribute which represents that pressure.

• PBV - Pressure Breaker Valves force a specified pressure loss to occur across the valve. They must have an initial_setting attribute which represents that pressure loss.

• FCV - Flow Control Valves limit the flow to a specified amount. They must have a initial_setting attribute, which is a float representing the flow setpoint of the valve.

• TCV - Throttle Control Valves simulate a partially closed valve by adjusting the minor head loss coefficient of the valve. They must have a initial_setting attribute, which represents the minor head loss coefficient of the valve.

• GPV - General Purpose Valves are used to represent a link where the user supplies a special flow - head loss relationship instead of following one of the standard hydraulic formulas. They can be used to model turbines, well draw-down or reduced-flow backflow prevention valves. They must have a headloss_curve attribute, which is a string representing the headloss curve of the valve in the form of a list of points, e.g. (0, 10), (2, 5), (3.3, 7).