Rainwater harvesting is the accumulation and deposition of rainwater for reuse before it reaches the aquifer. Uses include water for garden, water for livestock, water for irrigation, etc. In many places the water collected is just redirected to a deep pit with percolation. The harvested water can be used for drinking water as well if the storage is a tank that can be accessed and cleaned when needed.
Rainwater harvesting provides an independent water supply during regional water restrictions and in developed countries is often used to supplement the mains supply. Rain water harvesting provides water when there is a drought. Rainwater harvesting prevents flooding of low lying areas. Rain water harvesting replenishes the ground water table and enables our dug wells and bore wells to yield in a sustained manner. It helps in the availability of clean water by reducing the salinity and the presence of iron salts.
The concentration of contaminants is reduced significantly by diverting the initial flow of runoff water to waste. Improved water quality can also be obtained by using a floating draw-off mechanism (rather than from the base of the tank) and by using a series of tanks, with draw from the last in series. The stored rainwater may need to be analyzed properly before use in a way appropriate to its safety.
The quality of collected rainwater is generally better than that of surface water. Contamination is always possible by airborne dust and mists, bird feces, and other debris, so some treatment is necessary, depending on how the water will be used.
Components of a rainwater harvesting system
A rainwater harvesting system comprises components of various stages - transporting rainwater through pipes or drains, filtration, and storage in tanks for reuse or recharge. The common components of a rainwater harvesting system involved in these stages are illustrated here.
1. The catchment of a water