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Monday, May 25, 2009

Water Harvesting

What is rain water harvesting?

Water harvesting has been around for centuries and can be traced back through human history almost as far as the origins of agriculture.  Basically, rain water harvesting is the capturing and storing of rainfall to irrigate plants or to supply people and animals. Water harvesting involves a variety of methods used to get as much water as possible out of each rainfall. The great thing about water harvesting is that it will help you save money on your monthly water bills and reduce your dependence on municipally-supplied water as well as relieve stress on the environment and recharge groundwater tables. 

Planning Your Water Harvesting System

To put it simply, all you need for a water harvesting system is rain, and a place to put it. Your system can be simple, using contoured areas so that water flows directly to planted areas, or more sophisticated, using storage systems that can contain captured water for later use.  © 2009 Rainwater Solutions - "Continuous Guttering"

Types of Water Storage

You can store water in a variety of ways: steel drums, oak barrels or underground storage tanks, to name a few. One of the simplest forms of water harvesting is to place a drum or barrel on a raised platform under a rain gutter downspout. 

Rain Barrel

Usually a rain barrel is composed of a 50 to 55 gallon drum, a vinyl hose, PVC couplings, and a screen grate to keep debris and insects out. I have a very simple rain barrel at my house that captures water runoff from one-half of my home's roof and which I use to irrigate my garden throughout the summer months.

The rain barrel should have an external pipe with a shutoff valve to control the amount of water withdrawn. What I also did for my system is raise the rain barrel off of the ground to allow for greater head pressure. If this is not possible to do, a pump may be required to get the proper amount of pressure for your use, particularly if the water will be used as part of an irrigation system.  

Another important element is the overflow for excess water.  On my rain barrel system I have put a 6 foot garden hose that distributes the overflow water into a mini-rain garden that helps to contain and slowly disperse the water over-time, into the landscape.  It is important to keep the overflow water from spilling on the ground near the foundation of a home

System Maintenance

Regular maintenance is critical to any dependable water harvesting system. Make sure your gutters and downspouts are free of debris. Periodically clean and/or repair dikes, berms and channels to prevent excessive erosion.



Cisterns are another method of water harvesting and can be constructed of nearly any impervious, water retaining material.  They are distinguishable from rain barrels only by their larger sizes and different shapes. They can be located either above or below ground, and in out of the way places that can easily be incorporated into a site design.  Commercially available systems are typically constructed of high density plastics.  Cisterns can either be constructed on-site or pre-manufactured and then placed on-site.  

A simple method of construction, sometimes still utilized in rural areas, is to first lay a concrete floor in a small excavated area and then cover the dirt walls with several coats of plaster to assure water proofing.  If the cistern is dug correctly its round walls can then be capped with a concrete lid.  Small cisterns of up to 5000 gallon capacity have been constructed in this manner.

Materials utilized for the construction of cisterns can include redwood, polyethylene, fiberglass, metal, concrete, plaster (on walls), ferro-cement and impervious rock such as slate and granite.  Typical components of a cistern roof top catchment system include: the roof, gutters, and downspouts with connection to top of cistern, and outflow connections for appropriate uses, i.e., irrigation. 

Generally all rainwater tank/cistern designs should include these components: 

  • A solid secure cover
  • A leaf / mosquito screen at cistern entrance
  • A coarse inlet filter with clean-out valve
  • An overflow pipe
  • A manhole, sump, and drain to facilitate cleaning
  • An extraction system that does not contaminate the water (e.g. a tap or pump)


What are the advantages of rain water harvesting?
Lawn and garden watering make up nearly 40% of total household water use during the summer. A rain barrel collects water and stores it for when you need to water plants or wash car. Rain barrels provide an ample supply of free "soft water" containing no chlorine, lime or calcium making it ideal for gardens, flower or the potted plants. Also, according to the US Environmental Protection Agency, a rain barrel can potentially save most homeowners about 1,300 gallons of water during the peak summer months.

Through our research and exploration of rain water harvesting we came across several good sources of information that we wanted to pass along:

Book:  Water Storage : Tanks, Cisterns, Aquifers, and Ponds        by Art Ludwig
Website: www.harvesth2o.com - an online rain water harvesting community with lots of great information 
A useful guide put out by the North Carolina State University Extension

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