Water Harvesting
Water harvesting is one of the oldest ‘crops’ in the world. As long ago as 2,000 years, human civilizations have relied on rain to settle, sustain, and sow land of all variety. Deserts in the Negev, nomads in Africa, and elaborate Roman villas in Italy have all been designed to exploit the common aspects of rain collecting. The efficacy of the practice is testified to by the fact that water harvesting is still around today. The world’s largest existing water tank was built around 600 B.C. and remains standing and in use in Turkey. Remote areas are still dependent on some amount of rainfall for a variety of purposes…any one of which is part of the mosaic of human survival. Rain water allows for supplementary crop maintenance, dilution, human consumption, and support for a variety of livestock.Islands are common locations for water harvesting, especially using rainwater. Islands that are relatively close to a mainland often have water piped or carried in. Despite any distinctions between island and mainland rainwater harvesting, there are three common engineering elements: collection, conveyance, and storage. How these three interrelated elements are applied to their environment, however, vary greatly between urban and island environments.
One of the largest distinctions between urban and island rainwater collection is the same factor that prohibits water from being carried in to an island…the cost of shipping the materials. The costs of obtaining and constructing manmade materials to collect, convey, and store water on an island may be as much as the cost of shipping water to the island. Yet the pluses of rainwater are like pennies from heaven, too. Most island rainwater harvests are for far fewer people than their urban counterparts, and can often be developed from indigenous island materials. Best of all, rainwater is generally less polluted than underground water sources.
Roof water, land catchments, and run-off collectors are three major collection techniques. Land catchments and run-off collectors are, however, susceptible to contamination and tend to be very expensive. Roof water systems lend themselves to fairly easy installation and use. Because most people have a roof over their heads, it is also the most commonly used system. The rainwater simply runs down a roof slope, into a gutter, and along to a central drain. The creation of the water containment device (a cistern or simple ferrous cement tank) presents the most significant caution. There exists the possibility that water may need to be treated if intended for potable purposes.
Drafting
Growing up at the mouth of the Columbia River, my first experience in island living had to do with sustaining life that was not always human. You see, my father was raising cows on an island. The idea of a water-sogged cowboy was funny enough to make him a temporary celebrity…even appearing on CBS’s Walter Cronkite nightly news.
One of the common problems to be solved in island living is how to make sure any food you’re raising stays away from too much salt water. On one side of Sand Island was fairly fresh water. On the other side, the Pacific’s salt was too potent. Though desalination technology is finally approaching need, nature remains the preeminent tutor of water conservation. Island terrains, an unmoving lifeboat of geography, give proof of nature’s contradictions of engineering. When the Great Tsunami of 2005 struck vast island regions of Southeast Asia, after the obvious concern for immediate loss of life, were my thoughts of cattle…specifically, island cattle.
The result of salt water has been devastating to the eco systems and human sustainability on many archipelagos. One aid group’s study profiled the Andaman Islands. The findings, even after one year……….
Image Copyright Brad Lancaster and Joe Marshall
Resources
http://www.gdrc.org/uem/water/rainwater/rainwaterguide.pdf
http://www.harvestingrainwater.com/home
