Harvest the Rain A Presentation by the Vlahi Nature School This project was financed in part by USAID
Environmental Benefits Prevents runoff, erosion and flooding Saves energy Local, sustainable and clean water source Reduces pressure on ecosystems and watersheds if managed properly
Economic Benefits • Free water source • Save on energy costs • Reduces labor need • Increases crop productivity, which in turn reduces poverty • Other Benefits • Simple, but very effective • Ideal for rural, dry areas • “Rain water harvesting… is the most economical and surest way of providing water for drinking and sanitation even in the remotest areas.” – UNEP • Resource independence reduces the potential for conflict 105,000 liter collection system in Texas 2
How to Harvest Rainwater? • Rainwater harvesting is an ancient practice. Systems can range from extremely simple and inexpensive to highly complex and costly. • It all depends on your available resources, your goals and, most of all, the rain!
Simple landscape systems 3 • Gravity based • No storage device • Harvesting is done by a simple trench and landscape design • Planned slope and landscape architecture • No storage; distribution is done by the lot itself
Complex Landscape System 4 • Gutters installed to concentrate and direct flow • Rain is stored in a cistern for later use • Stored water is distributed as needed to plants via irrigation hoses
Key Components of Complex Landscape Systems • Catchment Surface (typically a roof) • Gutters • First flush diversion • Filters • Cistern or reservoir (with proper foundation insulation) • Irrigation or other outlet pipes • Overflow pipe
Filters for debris / insects First flush diversion Reservoir Concrete foundation Insulation Irrigation hose
First Flush Detail • Water comes down from the roof • The first rain collected is dirty from washing the roof so it goes to the down pipe, not the reservoir. • Once the down pipe is filled, water diverts to the reservoir, ensuring that the dirty rainwater is not stored • Diversion is mostly self cleaning via a drip on the T-outlet • Periodic full cleaning is possible by removing a plug at the bottom
5 Potable Rainwater System • Potable water outlet • Ultraviolet Lamp • 5 micron filter; 3 micron charcoal-activated filter • On Demand Pump • Non-potable Rainwater
Considerations for System Design: 6 • This map shows the proper process for designing rainwater harvesting • First, you must consider your needs and alternatives • Second, you must determine your available resources • Third, you must reconcile your needs and resources to design your system • Then, and only then, should you begin implementation • Generally, rainwater harvesting is not a “silver bullet,” but rather a source complementing other water supplies.
Conclusion: • Rainwater harvesting can be a great solution to many water resource problems. However, to maximize the benefits of rainwater harvesting, you must think about your situation and whether this technology is appropriate for you. • For more information, please see our manual on the basics of rainwater harvesting for drip irrigation and the resources on the next page.
Sources • http://www.nkba.org/green/glossary.aspx • Texas Water Development Board. “The Texas Manual on Rainwater Harvesting – Third Edition.” Austin, Texas. 2005. http://www.twdb.state.tx.us/publications/reports/RainwaterHarvestingManual_3rdedition.pdf • Worm, Janet and Van Hattum, Tim. “Agrodok 43: Rainwater Harvesting for Domestic Use.” Agromisa Foundation and CTA, Wageningen, The Netherlands: 2006. Accessed at: http://www.agromisa.org/agrodoks/Agromisa-AD-43-E.pdf • Images from: Waterfall, Patricia H. “Harvesting Rainwater for Landscape Use.” University of Arizona Cooperative Extension. 2006. http://www.azwater.gov/dwr/Conservation/files/Harvesting_Rainwater.pdf • Image from: Waterfall, 2006. • Image from: The Rainwater Observer. “Rainwater System Installation, Part 2.” http://www.rainwatercollecting.com/blog/?p=256. Accessed on: 02.07.2009 • Texas Water Development Board, 2005.