IAHS is a lively non-profit making international non-governmental scientific organization that serves the hydrological community worldwide. It started in 1922 and now has 11000 individual members, 11 commissions, four working groups and three committees. IAHS is linked with other associations and has interests in common with several UN bodies; particularly with the United Nations Educational, Scientific and Cultural Organization (UNESCO), the World Meteorological Organization (WMO) and the International Atomic Energy Agency (IAEA) and also with UN Water. Over the last decade IAHS and its Commissions have convened 6–8 conferences a year on specific topics, in addition to the Scientific Assemblies and General Assemblies within IUGG Assemblies. The tradition of publishing Proceedings and Reports of IAHS (Red Books) which commenced in 1924 at the Madrid General Assembly, has continued to the present. In addition IAHS has published the Special Publications Series (Blue Books), the Benchmark Series and the Hydrological Sciences Journal (HSJ). The HSJ was originally published as the Bulletin of the International Association of Scientific Hydrology (1956-1971); next it was Hydrological Sciences Bulletin (1972-1981), with four issues a year; and since 1982 is has been Hydrological Sciences Journal. The HSJ is now has 16 issues a year (more than 2900 pages per volume). The IAHS office is based at the UK Centre for Ecology and Hydrology, Wallingford, UK.