Newspaper article The Christian Science Monitor

Sand Dams: A Simple, Effective Way to Save Water in the Desert?

Newspaper article The Christian Science Monitor

Sand Dams: A Simple, Effective Way to Save Water in the Desert?

Article excerpt

The discovery of a lake the size of Delaware beneath a Kenyan desert this month may prove to be a game-changer for precious water needs in arid East Africa.

The new supply of billions of gallons, if managed properly, may make the desert bloom indefinitely, some scientists and UN experts say.

Yet in the mid-term, as Kenyan communities grapple with water shortages, many are starting to turn to something called "sand dams" to trap and save nature's precious liquid for use in times with no rain.

More than a thousand sand dams have been built in East Africa in the past decade in what is a simple, low-cost, effective way to store millions of gallons of water - by trapping it in piles of sand and later accessing it when rivers go dry.

Kenyans in the counties of Kitui, Machakos, and Makueni need water for crop irrigation, not to mention drinking. But their main rivers flow only seasonally.

Now, in a number of villages, local farmers are planting and harvesting all year long.

Sand dam technology may date to Roman times. But it has been perfected in the 21st century by a combination of talent including a British NGO called Excellent Development, a Kenyan farmer named Joshua Mukusya, and Mennonites from North America.

The dams are built by securing one or sometimes two long, reinforced concrete barriers across river beds, and by placing slotted PVC pipe deeper under the barriers. When it rains, the water carries sand downstream, depositing it up and around the level of the barrier.

At the end of the rainy season, water remains trapped in the piled-up sand, sometimes far downstream. Over time it drains into the PVC (a process that also helps with filtering and cleaning) and is then horded using a hand pump or a small run off pool - or in some cases a simple hole is dug at the base of the dam down to what has become a pool of stored water that can slake the thirst of 1,200 people for a year.

An average sand dam can store millions of gallons of water for years, and provide water for irrigation even when the rains fail, as noted at the first international conference on sand dams in Machakos, a town near Nairobi.

"We have literally turned arid and semi-arid lands into some of the most productive farmland. …

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