World Meteorological Organization
http://www.wmo.ch/

Global Water Partnership
http://www.gwp.org/

European Water Resources Association
http://www.ewra.net

The International Association of Hydrological Sciences
http://www.iahs.info

European Water Association
http://www.ewaonline.de/

The European Environment Agency (EEA)
http://www.eea.europa.eu/

The Water Page - All About Water Pollution
http://www.thewaterpage.com/water-pollution.htm

International Office for Water
http://www.oieau.fr/

Centre for the Assessment of Natural Hazards and Proactive Planning (CANaH)
http://www.naturalhazards.ntua.gr/