The basics of rainwater harvesting.



Rainwater harvesting is the accumulation of rainwater for reuse before it reaches the groundwater table. Harvested water can be used for gardening, indoor heating and cooling of houses, a water source for livestock as well as drinking water. Harvesting rainwater can reduce demand and need for water transport systems that threaten the health of the water cycle and our local environments.


Ironically, water use in developed countries often is highest in the places where rain falls the least. Rainwater harvesting is one easy and low tech solution in reducing domestic water use.

How to utilize rain water

The easiest rainwater source is that which falls in our gardens. Proper placement of plants, trees, and water collection areas can turn the site into a water efficient capture system. Shape the surface of the soil to slowly runoff, raise paths and terraces and sink all planting areas to collect the water. Choose plants, preferably native, that absorb and hold water in their root systems, or pass it down to the water table. This way, rainwater doesnít run off into the streets, where it would end up sewer systems or directly into a local waterway.

Store the rain in cisterns and barrels

An obvious source of rainwater collection is the roof. Even in areas with minimal rainfall there is a huge potential for harvesting water. For example, a roof of a 100 m2 can collect around 1000 litres per 10 mm of rain. Rain barrels are an easy way to harvest rainwater, especially in urban areas; they are low cost, and can be installed to work with existing gutters and pipes. There is a wide range of choices for storage tanks. They can be made from wood, metal, plastic, ferrocement or fibreglass, ranging in size from small to large.

Indoor use

All around the world itís becoming more common for people to use rainwater indoors for non-potable uses. These systems can reduce or eliminate the use of municipal or well water. Most household rainwater systems use a pump and pressure tank to pressurize water. Many countries however do not yet have codes covering indoor rainwater use, and people seeking permits may be required to filter and disinfect the water, increasing system cost and complexity. However, research has shown that rainwater harvested using a well designed system and protect the water from direct light is safe to use for laundry, bathing or flushing the toilet. Filtering only a small amount of water with passive filters such as a ceramic filter or with slow sand filters for drinking lead to a great reduction in system cost and offers an affordable solution for clean water.