A model can contain up to 100 sub-systems to aid the construction and maintenance of large, complicated models. For example, separate sub-systems could be created for a city's raw surface water assets, raw ground water assets, water treatment facilities, and treated water distribution.
Within a model of a treatment plant, each process module could be managed as a separate sub-system.
A sub-system is an assembly of the following types of objects:
Primary physical assets:
- chemical dosing points; and
- node junctions - where assets connect.
- consumption/demand - from a node on the model;
- head points - pre-defining variation in hydraulic level at a point; and
- bore drawdown - defining how an aquifer responds to abstraction flow rate.
Physical assets for surge protection:
- air cushions;
- air valves:
- anti-vacuum valves;
- pressure relief valves:
- pressure vessels:
- stand pipes: and
- surge tanks.
Notional devices for transient simulation:
- dummy long mains - to simplify some pipe networks.
The following parameters apply globally across all sub-systems in a model:
- types of consumption/demand; and
- their variation over time.
- pipe material characteristics;
- pipe classes; and
- sizes available within a pipe class.
- a set of valve build types; and
- variation of headloss with valve opening position.
- a set of generic pump types;
- variation of head versus flow rate and speed; and
- variation of torque versus flow rate and speed.
System control logic
- control blocks;
- definintion of instruments and controlled devices; and
- operational logic.
Electricity price tariffs
- pricing parameters; and
- time of day and periodic usage charges.
Source water quality characteristics
- a single type of source water;
- its first order decay characteristics; or
- initial concentrations and decay rates of multiple impurities in the source water.