[2] by virtue of the Water Act 1973[3] It took over the sewerage and sewage disposal responsibilities of the local authorities within its area, the roles and responsibilities of the six existing River Authorities in Wales and most of the water supply undertakings.
At inception, WNWDA was organised in units that broadly reflected the originating business.
In 1984 a major re-structuring brought all the functions together in three multidisciplinary divisions, with a headquarters in Brecon.
The chairman appointed by the government of the day was Lord Brecon but he was replaced by T. M. Haydn Rees in 1976[5] and then by John Elfed Jones in 1982.
In 1989 the water supply, sewerage, and sewage disposal functions of the authority were privatised to form Welsh Water with the regulatory and control functions passing to the newly created National Rivers Authority.