Tuesday, February 22, 2005

Wet Winter, Dry Summer: All about the rain

In the winter the skies open, the water pours down and people try their darndest to get rid of the stuff. In the summer, the sun shines, and shines, and shines, and the drought and dry come to visit, and suddenly: not enough water. Foolish? Stupid? Let’s just say, short-sighted.

How much water comes a calling in the average winter? (And the present one is way over the top, isn’t it?). 3 feet of rain in average over our watershed, and that’s convenient, since three feet of water on an acre is about a million gallons of water. Our watershed being 110,000 acres, that means the average winter rains are 110,000 million gallons. To wit: 110 billion gallons of water a year. (Or, 330,000 acre feet). Lots.

On the Plaza alone, using a reduced 30 inch average of rain for the city here, we receive 7 million gallons of rain. Lots.

And on a large sized city lot of 10,000 square feet, the rains bring over 200,000 gallons ( on lots you use the one cubic foot of water is 7.5 gallons figure). Lots even on lots.

So what’s the obvious solution? Save it in the winter? Right-o! Cisterns. Dry wells, a reverse well into which water is pumped all winter: these allow water to percolate back out into the soil and into the creeks in the summer, when it’s needed. In the hills, streams can be slowed with low tech solutions: fallen trees and boulders do just fine.

Also in the hills, swales would be swell. Swales, a concept the permaculture folks borrowed from a WPA experiment (wildly successful) in the 30’s, are long ditches dug ( by hand or dozer) along the contour on a hillside. Since they are on grade, all the water running down the hill has a chance to slow down, hang around and percolate into he ground.

Over the years, the zones just downhill from the swales become saturated with water, and even in desert climates, over time deeply shading trees can be grown there. Around here, the first three or four rows of vines below a swale ( which are put in about every 50 to 100 yards) could be free from irrigation. These swales obviously help with erosion, too.

So the sky has the rain and the land takes some, the trees need some, the vineyards and farms and pastures need some, but lots nowadays washes away in the winter into the creeks when they need it least. Meanwhile the humans in the Valley use less than 5 % of the amount of water that falls from the sky ( the City water district and Valley of the Moon District together use 6,000 acre feet a year, which is 2%), but we get very little of it from the sky, from our own watershed. No, we are busy robbing the watershed of the Russian River, a short-term solution that ignores our natural bounty.

Is this foolish? Stupid? No, just short-sighted.

Chris Elms
Sonoma, 996-1437

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