National
It’s under the establishment of UNESCO chair for water resources.
Regional (African and Arab countries)
http://www.arabwatercouncil.org
International
http://www.freshwateraction.net
http://www.rural-water-supply.net
http://www.safewaternetwork.org/
http://www.globalwaterchallenge.org/
http://www.globalwaterleaders.org/
Networks related to water harvesting
http://www.rainwaterharvesting.org