About water quality simulations

A water quality simulation can be used to track the movement and concentration of a single substance or multiple substances in the network over time.

The substance can be modelled in two ways:

• Conservative substance: only affected by transport within the network.
• Non-conservative substance: reacts with the network environment. The concentration will decay (or grow) due to these reactions. These changes are in addition to the effects of transport.

In addition to chemical transport, the water quality model can be used to calculate:

• Changes in age of water over time throughout the network.
• Percentage of water reaching a node in the network that had its origin at a specified 'trace node'.
• The dominant source providing most of the water reaching the node.

For technical details on the calculation of water quality simulation results, see Dynamic Water Quality Model.

Turbidity analysis can also be carried out as part of a water quality simulation. See Water quality - turbidity analysis for technical details.

For details on the model parameters required for a water quality simulation, see Water quality parameters and About water quality mixing controls .

Water quality simulation results

For general information on viewing simulation results, see Results.

There are additional results for nodes, which are not available when carrying out a normal run. These are:

• Concentration: the concentration at this node of the pollutant being modelled .
• Source Concentration: concentration contributed by any source at the node.
• Age of Water: average length of time the water has spent in the system before arriving at the node.
• Average Age of Water: time weighted average of Age of Water results calculated at each water quality timestep.

If one or more trace nodes are selected in the Water Quality Options dialog the following results are also available for nodes:

• Trace <node_ID> (%): percentage of water at this node that has originated from the named trace node.
• Dominant Source: indication of which source (trace node) contributes the most to water reaching the node.

Note: The dominant trace tolerance percentage may be adjusted in the Water Quality Options dialog.

There are additional results for nodes and links when carrying out a turbidity analysis. These are:

• Turbidity: turbidity at a node.
• Stored Turbidity Ratio: ratio of the amount of discolouration material to the total amount of such material bound to the pipe wall.
• Peak Turbidity: peak value of the turbidity in all segments in the pipe at the completion of the water quality time loop.

Notes on dominant source results

Dominant source results are derived from the trace percentage results. Results are numerical but are displayed in the nodes results grid as a string which includes the name of the trace node acting as the dominant source, or 'Mixed', 'Doubled' or 'Unknown' if a dominant source cannot be derived.

Numerical value	Results grid value	Description
-2	Mixed	Sources sum to 100% but no trace exceeds 50%
-1	Doubled	Sum of source percentages exceeds 100%
0	Unknown	Sum of source percentages is less than 100%
1, 2, 3... 10	Tr <trace number>:<trace node ID> e.g. TR 7:RZoneA	Sum of source percentages equals 100% (within a 5% tolerance) and the reported source node provides > 50% of water reaching the node.

The numerical value is used when graphing results involving dominant source results.

When using SQL queries compare the dominant source result with a string.

For example:

sim.TRACE_DOMINANT = 'DOUBLED'
sim.TRACE_DOMINANT LIKE 'Tr 7*'
sim.TRACE_DOMINANT MATCHES '.*RZoneA'

Note that the trace node string includes a space between the Tr and the trace number, except for trace 10 which is written as 'Tr10'.

See SQL Syntax for more details on the use of operators in queries.