SIRE is a information system for water network designed to get a better management for water network.
General information is available in french on https://www.vd.ch/themes/environnement/eaux/eau-potable/systeme-dinformation-des-reseaux-deau-sire/
The SIRE extension is an extension of QWAT datamodel, enabling equivalent exports towards SIRE format.
More about the extensions and customizations in QWAT :