The island of Sri Lanka, best known for beaches and Buddhas, features a lesser-known geographical phenomenon. Since antiquity, thousands of reservoirs have dotted the landscape. The reservoirs, large man made lakes called wewas, were associated with irrigation, agriculture, and the development of civilizations on the island. These massive public works projects, rebuilt through the ages, are still in use today, often cheek-and-jowl with rice paddies, another landscape feature I hope to explore in detail.
From what I've read, wewas allowed the ancient Lankans to grow two crops a year in their tropical, seasonally dry climate. A relative abundance of food provided the basis for what is today one of the most densely populated countries on Earth. Doubtless the wewas played a role in the development of a governing hierarchy as well as religious and social complexity we see today in Sri Lanka. (I promise to take notes and lots of pictures for future posts. Right now I'm betting that my iPhone5 stays home).
All of this is incredibly cool but the Lankans weren't alone in massive waterworks projects. In other posts I've written about the amazing canals of Xoximilco, south of Mexico City, a paradise of human collaboration with microbes, animals and plants.
Farther north in what is today the Salt River Valley of greater Phoenix, Hohokam peoples developed massive reverse-flow water systems that allowed for three crops a year and supported a population of hundreds of thousands of people. Trade based on Hohokam agriculture spanned thousands of miles and spurred enormous cultural interactions.
One last example. The Nabateans, a poorly known, semi nomadic group who inhabited the Negev Desert in what is today Israel, utilized water catchment techniques that allowed agriculture in one of the world's driest regions. I saw an example this past summer of a similar technique, low tech but highly effective, at the Hopi Second Mesa in Arizona.
Water and water use is such an enormous issue in contemporary society. We depend on vast expenditures to maintain technologies that support human endeavors of every sort. Here in the United States we exert punishing pressure on water resources, emptying ancient aquifers, introducing toxins to our freshwater, and abetting disastrous salinization in freshwater ground tables hundreds of miles from the ocean.
Whether these water management strategies are sustainable will depend on how well they (and we) adapt to future changes and contingencies. As we look to past civilizations we can see that long-term sustainability is never a guarantee in any climate.
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