What is Rainwater Harvesting?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 16 November 2019
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Rainwater harvesting is a process in which rainfall is collected and stored in large tanks, instead of being allowed to flow into a drainage system. People in regions of the world with limited water supplies have been using this technique to supplement available water for centuries, and the concept has also become a topic of interest among conservationists. By harvesting rainwater, people can reduce their overall water usage and confer a number of other environmental benefits.

Classically, rainwater is collected from a roof. In these systems, water from the gutters flows down downspouts linked to tanks of water, consolidating the water so that it can be used. People can also collect runoff from hillsides, streets, and other locations, using a variety of systems and setups. The collected water is not necessarily clean, because it may have flowed through contaminants on its way to the storage tank, but it can still be used in an assortment of ways.

One use for stored rainwater is in irrigation and gardening. Using rainwater cuts down on water bills, and ensures that good, potable water isn't wasted by being poured over plants and allowed to trickle away. In areas where conservation measures are common, residents may be strongly encouraged to consider rainwater harvesting for their gardening needs. Reduction of runoff also decreases the burden on storm drains, and reduces the number of pollutants which reach waterways and the ocean.


Setting up garden irrigation with collected rainwater is also fairly simple, and it shouldn't require a pump, as the tank can be mounted at an elevation so that the irrigation system will be gravity fed. Using a network of pipes and hoses, a gardener can set up a low-maintenance irrigation system, or a hose can simply be attached directly to the tank.

The collected water can also be used for things like filtering toilets, washing, and so forth. With the addition of filtration systems monitored by testing the water periodically, rainwater harvesting can also provide water for drinking, bathing, and cooking. It is generally not safe to use unfiltered rainwater for this purpose, as it can contain bacteria, viruses, chemicals, and other substances which are undesirable.

Setting up a rainwater harvesting system is fairly simple, especially if one wants a simple rooftop system. All one needs is large drums to place under the downspouts, or some pipes which can be used to connect multiple downspouts and route the water to a single collecting tank. It is also possible to purchase rainwater harvesting equipment designed for use on roofs, hillsides, and other locations. These systems may include filters, pumps, and other add-ons to make them more versatile.



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