Harvesting rain to irrigate conserves water
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Rainwater harvesting refers to the collection of rainwater to maximize its environmental and landscape value. Harvesting rainwater reduces storm water runoff volume and velocity and can provide an alternative water source to help conserve potable water supplies. There are typically three components in a rainwater harvesting system: 1) collection; 2) transports; and, 3) storage.
Collection generally occurs from rooftops or paved surfaces. The collected rainwater is then transported, often through downspouts or swales, and temporarily held in a storage device for future use. The rainwater also may be diverted to planted areas, such as a rain garden, for infiltration and use by plants, or directly infiltrated into the soil through permeable paving or an underground structure such as a dry well. Rainwater harvesting systems are classified as green infrastructure, which is targeted at collecting storm water to infiltrate and/or store for later use.
Using green space to capture and infiltrate storm water can be as simple as directing downspouts to planted areas or constructing small berms and drainage channels to direct rainwater to planted areas such as shrub borders or tree rows. However, rain gardens, bio-retention gardens, bio-swales and other planted areas installed specifically to infiltrate storm water will have greater impact.
Rain barrels are small tanks that store runoff, usually from a roof. Typically, barrels have a capacity of 55-100 gallons. While rain barrels are a good introduction to rainwater harvesting, they are limited in the amount of water held. Cisterns are usually over 100 gallons and they can be built above or below ground and some have integrated pumping devices. Other storage systems such as bladder tanks or dry wells can be adapted to any location for large quantity storage capacity and longer term holding.
Benefits of rainwater harvesting include: a relatively inexpensive supply of water that needs little or no treatment for most landscapes and livestock uses; decreased volume and velocity of storm water runoff leading to reduced stream bank erosion and fewer pollutants entering water bodies; reduced demand on public potable water supplies or private wells; increased soil moisture for improved plant root growth for increased drought tolerance and less irrigation.
Rainwater harvesting represents an opportunity to conserve water and help protect surface waters from pollution and erosion. By using rainwater harvesting systems, it is possible to take advantage of rainwater as an alternative source of water for non-potable uses; thereby also conserving drinking water and energy.
