Rainwater Harvesting Technologies: An Overview
A practical overview of rainwater harvesting, from rooftop and surface collection to fog harvesting and pump-and-store systems, and where each works best.
Why rainwater harvesting
Fast urban growth, falling groundwater, river pollution and recurring drought are putting cities and rural communities under water stress. Rainwater harvesting captures a resource that is otherwise lost, and it can be built at household, community and agricultural scale.
Rooftop harvesting
Rain is collected from a roof through gutters and pipes into a tank. Tiles and slate give the cleanest water, while painted or asbestos roofs are best avoided. With a simple vortex or floating filter, rooftop systems deliver clean water for households and small farms.
Surface-runoff harvesting
Rain flowing across the ground is diverted into a below-surface tank. Water quality is lower than direct rooftop collection, so storage is fenced and filtered. Examples include the clay-lined tajamares of Paraguay and community rock catchments in Kenya that harvest flash-flood water.
Fog harvesting
In coastal and mountainous regions, fog collectors trap water from fog on three-dimensional mesh nets. Well-sited units can yield hundreds of litres per net each day to drinking-water standards, serving rural communities across arid regions.
Pump-and-store
Where a stream or river is available, ram pumps move water to a storage tank with no fuel and near-zero running cost, letting farms store water in the wet season for use in the dry season.
How GIWEH uses this
GIWEH matches the technology to local rainfall, terrain and community capacity, and pairs it with training so communities can operate and maintain their own systems.