http://www.appropedia.org/Portal:Water

Water Portal at Appropedia -- good resource, many useful subcategories.

http://www.appropedia.org/Category:Water

Subcategories

There are 12 subcategories to this category.
Beyond dams
Greywater
Mosquito control
Pumping
Sanitation
Users interested in water and sanitation
Wastewater
Water and sanitation for developing countries
Water conservation
Water purification
Water quality
Water supply