Posted on February 20th, 2012

Outside the Box – Harvesting Rainwater

Water, affectionately and scientifically known as H2O, covers over 70% of the world. Ninety-six percent of this water is found in our oceans, and only 2.5% of our total supply is freshwater. Nearly 99% of the freshwater is in ice and groundwater. And what do people need to survive? Freshwater! UNICEF lists eleven countries as being extremely drought-stricken over a part if not all of its land base. All of these countries are in what many would consider the Developing or Third World. But it’s not just the Developing World that is in need of finding new sources of freshwater, many nations in the Western and industrialized world need to find new ways to make the use of the rainwater that falls on their soils.

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Rainwater harvesting has become a new method of efficiently using our natural resources around the world. This technique can be as simple as attaching closed 55 gallon garbage cans to the runoff from a housing gutter. People can use the water collected this way, or in other methods, for irrigation, providing water for livestock and in a purified fashion, use it for human drinking water.

In Australia it is common to have rainwater flow into a tank that is used for flushing toilets. In the United States, some states require you to buy a permit to harvest rainwater, as they retain all water rights. In Tokyo, Japan, the Ryogoku Kokugikan Sumo-wrestling Arena has an 8,400 m2 rooftop that collects and diverts rainwater into a 1,000 m3 underground storage tank for toilet flushing and air conditioning. In Thailand, citizens store rainwater from rooftop run-off in jars for drinking water. The jars range in size from 100 to 3,000 liters. The most common size is 2,000 liters and is sufficient enough to last a family of six for the six-month dry season.

The Gansu Province is one of the driest provinces in China. Annual precipitation is only 300 mm, and potential evaporation can be up to five times that. In 1995, the Gansu Provincial Government instituted the “121” Rainwater Catchment Project which aided farmers by building one rainwater collection field, two water storage tanks and sowing one piece of land to grow crops on. Within five years of the project’s inception, 2.2 million rainwater tanks were built that supplied water to nearly 2 million people.

Rainwater harvesting really is a sensible plan for everyone, regardless of water shortage in your area. Rainwater is sodium-free (important for people on low-sodium diets), reduces flow to stormwater drains, reduces summer demand peaks and helps delay expansion of existing water treatment plants. Rainwater can also eliminate the need for water softeners, and has zero-hardness which lengthens the life of appliances.

Across the country we are seeing more and more municipal and private agencies collecting rainwater. The Wells Branch Municipal Utility District in Austin, Texas captures rainwater and air-conditioning condensate from a 10,000 sq ft recreation center into a 37,000 gallon tank to serve as irrigation water for a 12-acre municipal park. The Lady Bird Johnson Wildflower Research Center in Austin harvests 300,000 gallons of rainwater annually from a 19,000 sq ft of roof collection for irrigation of its native plant landscapes. So the progress is positive. Collecting water leads to saving resources, and saving money. Isn’t that a cool drink of water?

Justin Harmon

Staff Writer

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