Harvest From the Sky
If you've ever opened your mouth to the sky during a rainstorm you have--for fun--"harvested" rainwater. Harvesting is the term water experts use to describe the process of capturing rain before it has a chance to soak into the soil or run off into streams.
Today, rainwater harvesting is far from child's play. This ancient yet underused practice is being revived as a simple, inexpensive and effective response to the challenges of living in dry areas where every raindrop is precious.
Rainwater jars from Sri Lanka are made of durable materials and may hold as much as several thousand liters. Gutters funnel rain from the roof into the mouth of the jar, which is covered with mesh to screen out leaves and other debris. People draw water from a tap at the bottom. Collecting rainwater this way is a popular technique throughout Southeast Asia, where yearly rainfall may be concentrated in a few weeks.
In Australia, rainwater is the sole source of household water for three million rural people and is being adopted as a supplementary supply by some cities. In Melbourne, rain collected from the roofs of tall buildings is used to irrigate a nearby park.
Harvesting the Rain
For thousands of years, people in dry places have engineered channels, dams, and storage pools in order to capture what rainfall and runoff there is. Large cisterns in locations like Yemen have steps down to the water level. In recent decades drilled wells have become more widely used in Yemen and around the world. But in many places, people have rediscovered the benefits of harvesting the rain.
By the Numbers
Much of Asia gets 90 percent of its yearly rainfall in 100 hours.
Rain was an important source of water in the ancient trading city of Petra, Jordan, which supported a population of perhaps 20,000 in a place where a mere 15 centimeters (six inches) of rain fell a year. Surface channels cut high in the cliffs surrounding the city led rainwater into huge, multi-chambered cisterns, which also held water from three springs. Archaeologists think these reservoirs held millions of liters of water.