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Residential Water Harvesting Systems; an Introduction


Water Harvesting with Gutter and Rain BarrelA rainwater collection system harvests rainfall from roofs or other waterproof surfaces. Residential rainwater collection uses water captured and stored at a home or other type of residence. The system connects the roof, gutters, and rain barrels to gather rainwater and store it for later use. Since homeowners will use the water on the site of collection, there is no need to transport it to other locations. A residential rainwater irrigation system is a sustainable system that saves money and conserves public water.

There are significant benefits of rainwater collection, and homeowners and residents can use rainwater to nourish trees, gardens, flower beds, and yards. The typical components of a basic system are downspouts from the roof level, a modified gutter system, pipes to carry water, and rain barrels for storage.

The benefits of rainwater irrigation setups are amplified in water scarce areas  (e.g. Los Angeles), but they’re valuable in many climates. These benefits include:

• Water conservation

• Saving money on utility costs

• Positive environmental impact

• Increase the value of a home or residence

• Reduce damage to home and foundation from rains and water

Good Citizenship

People concerned with water usage, their impact on the local ecosystem, and water conservation consider residential rainwater collection as a contribution to their community. Rainwater is free, and it does not require tax-supported action by the local government. Using rainwater reduces the demands on the local water treatment system. A community with widespread usage of rainwater collection will send far less rainwater into the local water system. The basics of rainwater collection and irrigation are usually already in place. A roof area receives many gallons of water during rains, and the gutter system carries it away. The system adds rain barrels or other collection containers to hold the water until needed.

Practical Applications

A rainwater irrigation system can be a simple arrangement that directs rainwater to a garden plot or flower beds. Or, they can be expansive systems that can irrigate large areas of ground. The structure of a rainwater irrigation system can range from a downspout and barrel to sophisticated contractor-installed systems for all types of water usage. Many people prefer to do it themselves, and the DIY rain collection and irrigation systems can be quite effective, creative, and require low-cost investments of time and materials.

Rainwater is an excellent source of water for plants, shrubs, flower gardens, and landscapes. Rain does not have chlorine, fluorine, and other trace elements that can build up in the soils and affect plants and foliage. Gardeners have valued the benefits of rainwater for their flowers, shrubs, and vegetables, and organic gardeners make strong efforts to avoid adding chemicals to their plant beds and soils. Many gardeners began with a simple barrel for rain collection.

Rainwater harvesting can be a primary source of water. Like wells, rainwater collection can provide water for outdoor irrigation and indoor uses like clothes washing and cleaning. With more advanced systems, households can convert rainwater into safe drinking water.

Rainwater collection systems have a wide range of uses; there is also a wide range of investment to start or maintain a rainwater system. On the basic end of the scale, an effective rain barrel is a covered or enclosed container with a connection for water run-off from a roof and a tap near the bottom for letting out water. Some projects modify trash cans for containers while others begin with a purchase of a commercial rain barrel. The size of the tank can vary, and the capacity will determine the amount of water that the system can hold.

Directing rainwater away from the foundation of a home or residence can have an overall beneficial effect to prevent flooding and foundation damage from excessive groundwater. By directing rainwater away from the structure, the ground will provide better support and stay drier than if left to absorb rainwater.

Calculating Rainwater for Irrigation

You can easily calculate the amount of water captured by a rainwater irrigation system. You must know the approximate dimensions of the water collection surface, such as a roof of a home or other type of building. A typical roof area can provide surprising amounts of water. For example, one inch of rainfall on a roof that is 20 feet by 20 feet can provide 220 gallons of rainwater.

The list below sets out the formula for calculating rainwater harvests.

A = Length of the roof area

B = Width of the roof area

C= The amount of rainfall in inches

The formula is A x B x C = the amount of rainwater in gallons.

The average roof size is about 20 feet by 40 feet. In one hour of moderate rainfall, a roof this size can shed about 600 gallons of water. Across the US, a typical household might use about 40 percent of its total water usage on outdoor irrigation or similar uses.

Water Collection Basics

Rainwater is heavy, and the system for storage must support the weight of water. Simple barrel set-ups typically have support for the barrel and sit on a bed of gravel to promote water flow and avoid creating muddy areas.

Water collection containers or barrels can work as a single container or have connections and link two or more containers to handle overflow and regulate irrigation. Containers should be covered and well maintained. They require periodic cleaning.

The gutters on the roof are part of the water intake, and a successful system must keep the channels free of debris that can clog the system and interfere with water collection.

Advantages in Water-Scarce Locations

In water-restricted areas, rainwater irrigation systems can save money, reduce harmful environmental impacts, and provide the freedom to use water wisely and effectively. The goal of water conservation is to allocate a scarce resource fairly. Governments do not intend to limit homeowner freedom. Using rainwater for irrigation promotes community efforts to conserve treated water.

Many areas of the US have regular or frequent water restrictions. Restrictions vary and depend upon location. Typical examples are limits on the time of day for using water to water lawns, restrictions on the use of water for outdoor pools, and day of week restrictions on lawn irrigation. The summer months, in particular, can have severe limitations on the use of public water systems. In water-restricted areas, rainwater irrigation systems provide a useful water supply that governments cannot restrict or regulate.

Water restricted areas also add costly fees and surcharges to encourage conservation. The extra fees and high water usage charges can add up and become a burden for many residents in water-scarce areas.

Residential rainwater irrigation systems can be elaborate arrangements requiring substantial investments and contractor installation. They can also be a simple roof, gutter, and rain barrel arrangements. Any type of rainfall harvesting helps conserve public water and reduce the demands on local water systems. Homeowners can reduce their utility costs and promote the local ecology at the same time.

Back to the Basics

For centuries, people have used rainwater to irrigate land, gardens, and other growing areas. Today, people across the US have rediscovered the benefits of rainwater. In a water-scarce region, rainwater collection can make a substantial contribution to conservation. At any level of price and investment that you may choose, there is a residential rainwater system that can meet your needs.


More Reading:

LA County’s public watershed program has put together an excellent overview for those interested in how to put water harvesting into practice at their home.

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