Tree People Cisterns: http://www.treepeople.org/cistern
The coolest interactive demonstration I've seen in awhile from a nonprofit organization allows you to model out your own cistern project and look at rainfall collection as it can be used throughout the year for agriculture, fire safety & other essential needs.
This allows for easy water collection across a whole village area, reducing the need to hike long distances or drill for water in desert regions that receive some rainfall during a rainy season.
Cisterns are fabulous inventions that have been around for centuries -- in Los Angeles the Tree People put cisterns beneath schoolyards so that they can keep grass year-round without watering from an outside source. Cisterns in other regions provide essential drinking water in places where no other options exist, such as island nations where all ground water is salt. Rain catch systems can be a beautiful sculptural addition to areas where the flow of water is essential for aeration. In other regions consider closed systems to reduce environmental contamination: for example regions such as Haiti where sanitation issues are extreme during rebuilding and cleanup.
How big is the cistern?
The TreePeople cistern is a circular tank, 70 feet in diameter and 8 feet deep. It is made of concrete and has a steel-reinforced roof held up by concrete pillars. This enables it to withstand the weight of fire trucks in times of emergency – when the water in the cistern can be used by our local fire department.