Priority of supply connections

Here, the priority of supply connections and the supply rules are specified.

By default, supply connections are given a priority according to the sequence in which they are digitised. The priority can be changed in the priority column. Number 1 has first priority; number 2 has second priority, and so forth.

Two types of supply rules are available:

·         Call by priority: Water is supplied to satisfy the demand in the order of priority beginning with the supply connection with the lowest ‘priority number’.

·         Fraction of demand: Water supply is based on the fraction of the demand required from each supply connection. If a supply connection cannot fulfil its fraction there is no attempt to extract water from another supply connection.

A fraction file, containing the fraction of demand requested from each supply connection must be specified.

This is done by clicking on the  button and clicking Browse... to select an existing fraction file or clicking Create a new file… to open the ‘Create a new file’ dialogue.

Note: The sum of fractions must not exceed 1. It is possible, however, to have a sum less than 1, with the remainder showing in the results as “Water Demand Deficit”. Be careful, however, as it can be hard to dis­tinguish this deficit from a “true” deficit due to lack of water.

It is possible to use a combination of Call by priority and Fraction of demand by assigning the same priority to one or more groups of supply connections and then specifying the fraction of demand required from each supply con­nection within the ‘shared priority’ group. The fractions for all supply connec­tions within a ‘shared priority’ group must add up to one at all times.