rainwaterharvesting

Rainwater harvesting refers to the collection, storage, and use of rainwater from surfaces such as rooftops for later use. It encompasses a range of systems from simple barrels to complex subterranean cisterns. The basic components are catchment (the roof or other surface), conveyance (gutters, downspouts, piping), storage (tank, cistern, or underground reservoir), and distribution (gravity-fed taps or pumped supply) with treatment steps as needed.

Common methods include rooftop collection with a first-flush diverter to exclude initial runoff, and recharge of groundwater through infiltration trenches or basins. Treatment can include screens, sediment filters, disinfection, and, for potable use, more advanced systems.

Applications vary from irrigation of gardens and landscapes to toilet flushing, laundry, and, with appropriate treatment, potable supply. In drought-prone regions, rainwater harvesting reduces demand on centralized water systems, lowers urban runoff, and can provide cost savings, though yields depend on rainfall, roof area, catchment efficiency, and system maintenance.

Risks include water quality concerns, stagnation and microbial growth, mosquito breeding, and potential contamination from roofing materials. Regular maintenance, backflow protection, and appropriate filtration and disinfection are essential. System design and use are subject to local regulations and standards, which can specify allowable uses, materials, and cross-connection protections.

Historically widespread in arid and semi-arid regions, rainwater harvesting has gained renewed attention as a sustainable water management practice globally.