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Rain Water Harvesting

Posted on 04 May 2011



Books have been written on the subject of Rain Water Harvesting…especially focusing on parts of Africa, like Jordan.  With severity in climates increasing here in the US, more attention is focused on some very pertinent concepts.  Water harvesting is the simple accumulation and directing of rainfall for reuse in a yard, garden, landscape or for livestock drinking water. Rainwater harvesting is the process of intercepting storm-water runoff and putting it to beneficial use.

Recent studies claim over 97% of precipitation never makes it to Colorado streams as plant life sucks it up or it evaporates.  Rainwater harvesting is a great way to augment precious household water supplies, while at the same time actually helping to conserve water by reducing demand on municipal supplies.

In most areas of Colorado, the most common way to use rainwater is to direct roof gutter downspouts to landscape areas you wish to water. Recent legislation allows limited collection and use of precipitation from residential property rooftops in cases where the landowner uses or is entitled to only certain types of well permits to use well water for their domestic non-potable water supply.

Most experts agree several principles need to be followed for successful water harvesting.

1. Begin with long and thoughtful observation of your surroundings
Use all your senses to see where the water flows and how. What is working, what is not? Build on what works.

2. Start at the top (highpoint) of your watershed and work your way down
Water travels downhill, so collect water at your high points for more immediate infiltration and easy gravity-fed distribution. Start at the top where there is less volume and velocity of water.

3. Start small and simple
Work at a scale so you can build and repair everything. Many smaller strategies are far more effective than one big one when you are trying to infiltrate water into the soil whether it is primarily for one property or many.

4. Slow, spread, and infiltrate the flow of water
Rather than having water erosion run off the land’s surface, encourage it to stick around  and infiltrate into the soil. Slow it, spread it, and get it to sink in.

5. Always plan an overflow route, and manage that overflow as a valuable resource
Always have an overflow route for the water in times of extra heavy rains, and where possible, use the overflow as a resource.

6. Maximize living and organic ground cover
Create a living sponge so the harvested water is utilized effectively to create more resources, while the soil’s ability to infiltrate and hold water steadily improves over time.

7. Maximize beneficial relationships and efficiency 

Get your water harvesting strategies to do more than hold water. Berms can double as high-and-dry raised paths. Plantings can be placed to cool buildings in summer. Vegetation can be selected to provide food. Mulch can be used to assist in even water distribution as well as lessening the amount needed to maintain the soil or plants.

8. Continually reassess your system

Observe how your work affects the site, beginning again with the first principle. Make any needed changes, using the principles to guide you.

Rain in urban and industrialized areas may contain various impurities absorbed from the atmosphere, including arsenic and mercury. In Colorado, rain is infrequent, but rainwater quality is generally good. However, the infrequency of rainfall results in accumulation of bird droppings, dust and other impurities on rooftops between rain events. These impurities may occur in high concentrations in rooftop runoff when it does rain. The best strategy is to filter and screen out contaminants before they enter the storage container. Dirty containers may become a health hazard or a breeding ground for mosquitoes and other pests.

Due to concerns surrounding microbial contamination of harvested rainwater, it is not recommended as a source of drinking water for humans. However, properly designed, constructed, and maintained systems that include disinfection steps have been successfully used for private domestic water supplies.

Check with the Colorado Division of Water Resources and your local building, zoning, and environmental departments before you develop a rainwater harvesting system to determine what plumbing requirements, local restrictions, neighborhood covenants, or other regulations or guidelines might apply to your project.

Written By Janine Buchal


1 Response to Rain Water Harvesting

  • Ken says:

    A few years ago, I was told by someone in the Aurora Government that harvesting rain water was illegal. Have things changed, or is Aurora just acting foolish?

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