Rainwater Harvesting....

Rainwater harvesting is the capture, storage and utilization of rainwater for a meaningful purpose. There has been a huge spike in rainwater harvesting systems across the United States as a result of drought, increasing population and aging infrastructure. Rainwater harvesting offers many benefits, which include conservation of groundwater, low on salts, gravity systems help to conserve energy and can reduce flooding and erosion. 

Commonly, rainwater harvesting methods are isolated into two categories, passive and active systems. Passive systems utilize no moving parts and generally use the landscape for rainwater diversion to a desired locality. The water is stored in the soil rather than a containment object for a Passive System. Passive systems include rain gardens and permeable pavements.

The design of rainwater harvesting systems will vary for each building type. A usual system will consist of three components, which include the catchment, the detention basin, and the conveyance system, but the most important element is the catchment, which is used to collect the rainfall. The catchment can be on the roof depending if it is flat. 

If the roof were sloped then there would be some form of collection area or gutter on the overhangs that will lead to the detention basin. Since, rainwater is considered, in terms of it being potable, in between groundwater and surface water then passing it through a sand filter will sufficient and adding baking soda to increase its pH to the desired level will work as well.

An example of a complex rainwater harvesting system that is used is the HighDRO system. This system consists of a flush filter, rainwater collection tank and an advanced water filtration/disinfection system. This system can help a building achieve Net-Zero Water, but it could cost the building in becoming a Net-Zero Energy building if the energy requirement is high.

Rainwater harvesting shows great potential to reduce municipal water supply costs and protect adjacent ecosystems. The U.S. EPA reports that “reducing [municipal] potable water demand by 10 percent could save approximately 300 billion kilowatt-hours of energy each year” in the U.S. alone.

Best practices for designing rainwater-harvesting systems use relatively simple, little technological methods for collection and the storage. Water should enter the cistern near the bottom of the tank where it is subsided by means of a diffuser to avoid disturbing sediment in the tank.

Rainwater harvesting systems have the potential for incorporation into a wide number of other building systems. “They are ideally suited for incorporation into on-site stormwater management strategies, allowing temporary storage after storm events and helping to reduce runoff.” They are also ideal for use in landscape irrigation, counteracting the need for potable water.

 Further occasions may exist to integrate rainwater cisterns into both active and passive solar systems by providing a potential location for storage of thermal energy. Large storage tanks may both provide or require additional structural support so careful attention is needed when designing them either on or near other structures. Finally, catchment and conveyance systems may be integrated into both interior and exterior spaces of a building in such a way that they provide a valuable connection between occupants and the natural water cycles outside the building.