Thursday, August 7, 2008

"Free" Rain Water, Cisterns

Jean de Florette, a film by French director Claude Berri, is set in the scrubby, olive tree-covered hills of southern France. As the film begins, a severe drought has dried up a family's cistern—the underground stone storage tank for rain from a roof covered by a terracotta tiles. A farmer, played by Gerard de Pardieu (of Green Card and Cyrano fame), watches helplessly as his family's crops begin to wither and their cash crop of meat rabbits begins to die of thirst. Two peasant farmers plot to force the neighboring family into bankruptcy. Finally, the two conniving farmers manage to cause the early death of the Pardieu's character, to destroy his family and to acquire the farm for much less than the pre-drought price. All because the cistern was too small to store enough water for the driest years.

For better or worse, cisterns are used throughout the world to catch rainwater from the roof for drinking, washing, and irrigation. Cisterns come in all shapes and sizes—rain barrels, stone wells, ugly black plastic drums, and nondescript gray concrete tanks. In the 1800’s and early 1900s in America, cisterns were common, even in cities.

But the uses of cisterns and the reasons for building your own have changed. Cisterns are experiencing a welcome and well-deserved revival, due to dwindling sources of clean water, erratic supplies during droughts, and a renewed interest in water independence.

Cistern systems are remarkably simple compared to many modern technologies such as wells, and a complicated infrastructure. Basically, the rain must be gathered, stored in a cistern [now loosely defined as any tank in- or above the ground] and drained or pumped to the landscape. In most cases, rainfall is collected from the roof of the home, barn, or garage. A typical gutter funnels the rain into a downspout, hose, or pipe which leads to the cistern itself. A diverter valve is built in the downspout or pipe so the first rains after a dry spell, to flush all kinds of accumulated filth off the roof, can be turned away from the cistern until the roof is clean. Usually, a simple device or grate screens out any twig and leaf debris which may have gathered on the roof. Commonly, modern cisterns are concrete or plastic tanks.

Drought-Proof Your Garden—yes and no
Droughts are often the single source of inspiration for the installation of cisterns throughout the South West, if not everywhere. The recent changes in the climate see to be making much of the South West more parched than years past. As early as the drought of the 1990s, gave rise to the interest and need for water storage.

Ironically, cisterns in regions with no summer rain whatsoever are expensive propositions. In such an area, you must store up enough water for as much as six months of landscape irrigation. Consider, for example, an anonymous two-acre estate in a wealthy neighborhood in Santa Barbara, California, planted with water-loving ornamentals, some drought-resistant plants, a large 1/2-acre lawn, and a vegetable garden. During the drought, such a landscape, based upon the conservative figure of outdoor use equaling 60% of all water use, had a historical year-round usage of a staggering 500,000 gallons! A cistern big enough to hold this much water would have to be a whopping 50 feet on each side and 27 feet tall! Try and hide that in your average backyard. Such a cistern would cause a severe drought in your cash flow.

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