The Water Authority of Western Australia held responsiblity for the construction, operation, maintenance and control of water, sewerage and main drainage facilities within the State. The Water Authority was formed in July 1985 and merged the Metropolitan Water Authority with the country water activities of the Public Works Department. The Water Authority was replaced by the Water Corporation on 1 January 1996.

Following the election of a Labor government to office in October 1911, legislation was introduced to amalgamate the various water supplies throughout the State. The new Department assumed responsibilities for the following activities on 1 August 1912:

• the Goldfields Water Supply undertaking;
• the Metropolitan Water Supply, Sewerage and Drainage undertaking;
• Agricultural and Country Town water supplies, Irrigation and drainage, artesian boring;
• water supplies, stock routes in Mining Districts.

(North West water supplies continued to be managed by the Engineer for the North West in the Public Works Department)

The Under-Secretary of the Department was H.C. Trethowan and the two joint engineering heads were Hugh Oldham for Metropolitan and Agricultural areas and P.V. O'Brien for Goldfields and Northern Areas.

During the life of the Department, projects of major importance included the overhaul of the Coolgardie water supply pipeline and the beginning of the irrigation scheme at Harvey.

In 1914 the Metropolitan region was expanded to include Armadale, Guildford and Midland. During that year Perth, Fremantle and Claremont were consolidated into a central district. During 1916 and 1917 local councillors and Liberal politicians pressured the Government to reinstate Board control for the Metropolitan concerns. Between April and June 1918, the latter's functions were split administratively from the rest of the Department. Both organisations remained part of the same Department until 1921. In that year the MWSS & DD was established and the Public Works Department assumed formal control of the country operations.

This organisation was established in 1910 pursuant to Statute No. 43 of 1909. The Act consolidated water supply, sewerage and drainage schemes under one administration, directly responsible to the Minister of Water Supply, Sewerage and Drainage.

Between August 1912 to April 1918 the Department was administered by and integrated with the Water Supply, Sewerage and Drainage Department (MWSS & DD). The MWSS & DD's status as a separate Department was not re-established until July 1921.

In October 1925 the Engineering staff of the Department come once more under the direct supervision of the Public Works Department's Chief Engineer. There was thereafter a pooling of staff resources, and accommodation between the two Departments. Three water supply, sewerage and drainage districts were gazetted as constituting the Metropolitan Area in January 1910. These districts were Perth, Claremont and Fremantle where water supply and sewerage schemes already existed. In 1914 Guildford, Midland and Armadale were also included in the Metropolitan Area.

In September 1963 the Liberal Government introduced a Metropolitan Water Supply Sewerage and Drainage Amendment Bill with the intention of substituting Board for Departmental control. The Act was promulgated in November 1963 and a new administrative structure established by July 1964.

The Metropolitan Water Supply Sewerage & Drainage Board was established on the 1 July 1964 to operate as a Board with borrowing powers similar to other State owned enterprises. The Board initially consisted of seven members, all viceregal appointees.

The Authority came into existence as from the 1 July 1982 pursuant to Statute 36 of 1982. This Act was the result of a legislative review conducted since 1978 with the intention of gradual replacement of obsolete provisions of the 1909 legislation (No. 43 of 1909).

The new legislation provided that "subject to the Minister, the Authority shall be administered by a Board of Management to be known as the Metropolitan Water Board". The Board consisted of seven viceregal appointees three of whom were Authority employees, and four, external appointees. The Chairman was appointed by the Governor for five years. The property, powers, functions (etc) of the former Board were transferred to the Authority by the new Act.

Following the election of a Labor Government in February 1983, a steering committee was appointed to oversee the merger of the Authority and related water activities of the Public Works Department. The new omnibus organisation (i.e. the Water Authority of Western Australia) received legislative basis through the Water Authority Act of 1984. The new Authority commenced operations as from 1 July 1985.

The Water Corporation was established as a body corporate under the Water Corporation Act 1995 and assumed the functions of the Water Authority of Western Australia on 1 January 1996. The Water Corporation is now the principle water utility for Western Australia and provides water, wasterwater, drainage and irrigation services to the State.