It has permanent staff housed in its headquarters and global secretariat in central London, the United Kingdom, to support the activities, and has a regional office in Chennai, India.

IWA features regional associations, approximately 50 specialist groups covering key topics in urban water management, specialized task forces, and web-based knowledge networks.

[1] On 23 January 1998, the then presidents, Nicholas Hood of IWSA and Thomas Keinath of IAWQ, signed a memorandum of understanding, paving the way for the ratification of the merger between the two organizations.

[8] After receiving mandates from their respective boards of directors to the formal proposal, IWSA in May and IAWQ in June the same year, the full merger was scheduled to take place by 1 August 1999.

[1] Under UK Charity Law, the merger officially dissolved IWSA and IAWQ, giving rise to the establishment of a new association.

[20][21] On 1 September 2016, the World Bank and IWA announced the establishment of a partnership surrounding the reduction of water losses.

[22] In a partnership with OPEC Fund for International Development (OFID), the IWA published a report on 26 February 2017, emphasizes the critical need for swift and substantial action to significantly enhance wastewater treatment, reuse, and recycling.

[23] At an official ceremony on 14 November 2007, a major operational office in The Hague, the Netherlands, was opened, which followed the opening of regional offices in Beijing, Republic of China (7 December 2006) and Singapore (5 June 2007), and later in Nairobi, Kenya (2009/2010), Bucharest, Romania (24 November 2009) and Milwaukee, Wisconsin, United States (2016).

[24][1][21][25][16] A regional office in Chennai, India was established in May 2018 to coordinate the organization's activities across South Asia, and hosts a sub-unit of the IT and Digital Transformation team.

[7] A collaboration agreement that established IWA's new Global Operations Hub in Nanjing, Republic of China, was signed on 22 October 2018 to host the Asia & Oceania Regional Member Engagement and Service, Water Intelligence, IWA Learn, and Event, becoming fully operational in July 2019, and staying active until late 2022 or early 2023.

[1] The length of the presidency is a two-year term of office, which can be renewed for a second mandate following a constitutional change at a Beijing meeting in 2006.

[7] The association's work and strategy is guided and directed by its Governing Assembly, Board of Directors, Strategic Council and committees.

They were tasked with overseeing a two-year transition period from September 1999 through October 2001 (the IWA Congress in Berlin) as the newly formed organization, worked towards operational establishment.

[27] Due to a delay caused by the COVID-19 pandemic, the presidency of Tom Mollenkopf became effective in May 2021 despite being elected for his first term in October 2019.

IWA Publishing Ltd. (IWAP) was established as the wholly owned subsidiary of the International Water Association in January 1999, in anticipation of the merger between IAWQ and IWSA, with the purpose of providing information services on all aspects of water, wastewater and related environmental fields, and would take over journal, book and magazine publications from the previous associations.

[46] The company's portfolio include the publishing and printing of periodicals and a broad range of peer-reviewed scientific journals alongside over 800 books, research reports, manuals of best practice, and online services.

[49] A member and trade exhibition magazine, named Water21 was launched to coincide with the creation of IWA, publishing six issues each year with a worldwide circulation of approximately 20,000, and combining elements from the previous periodicals, IAWQ's Water Quality International and IWSA's Aqua News.

[60][61][62] The Leading Edge Conference on Water and Wastewater Technologies (LET) have been held annually since the first edition at Noordwijk, the Netherlands in 2003, with the exception of years 2020–2021.