Friday, November 7, 2008

Gamone water puzzle

Urban folk often forget about water... unless their administrators happen to inform them suddenly that the municipality might be running out of water. Here at Gamone, I've always been interested in the water situation. In 1994, I was the first resident in my small neighborhood to be connected to the municipal water supply. Before then, my Gamone predecessors had to depend upon a spring, fifty meters beyond the house. Since my arrival, I've taken advantage of this spring water to water my garden. Unfortunately, it ceases to flow during certain dry periods of the year. A local acquaintanceRené Uzel, younger than me, who lived here at Gamone for several years when he was a child—told me that, during the dry periods, they had to drive down to the village to bring back water for the family.

These days, at Gamone, it's wet periods that create a problem. I've been troubled by a puzzle, illustrated in this diagram of my spring:

Spring water accumulates constantly in a small pool up above my house, surrounded by high banks. A concrete tank, marked captor, collects the spring water. This tank, with a steel lid, is located well above ground level, just outside the banks of the spring pool. This captor tank is perfectly accessible, and I can verify constantly that it's functioning correctly simply by wandering up to the Gamone spring and lifting the captor's lid. At the outlet marked spring, a garden hose takes the water down to a sprinkler on the lawn alongside my house. Consequently, for many months during the year, my lawn is watered non-stop by the spring... even when it's pouring rain!

In this idyllic context, the only problem is the existence of a massive spill (as indicated in the above diagram) whenever there's a lot of rain up above Gamone. This spill is of a brief duration (no more than a week, two or three times a year), but the excess water hurtles down the slopes in the form of a small but powerful torrent, particularly since the municipality has laid a bitumen road above Gamone, crossed by steel gutters that focus the flow. Recently, the spill from Gamone's spring has started to provoke minor landslides below my property.

Now, here's the puzzle: Is this spill water in fact a subterranean overflow from my spring, which might be collected by reconstructing the present captor? Or is it maybe an autonomous underground channel [unlikely hypothesis], unrelated to my spring? The most intriguing item of information is that, when the spill ceases, the captor continues to supply spring water to my lawn. Obviously, if the spill were fed by leaks down at the bottom of the pool marked Gamone water, then the spring and the spill should be synchronized, as it were. As soon as one stops or starts, the other should stop or start at almost the same time. So, how can we explain the puzzle? Why does the spill only occur after heavy rainfall above Gamone, and why does the spring continue to supply water well after the spill has ceased?

Yesterday, for the first time ever, our municipal employee Pierre Faure ventured a logical answer to this puzzle. The spill is the outcome of leaks, not at the bottom of the pool, but around its upper edges.

Pierre's simple explanation enables everything to fall into place (including the water, you might say). After heavy rain above Gamone, the level of the spring pool rises, due in part to ground-level rivulets. When the surface of the pool reaches the level of the external fissures around its perimeters, the spill starts. I insist upon the fact that this phenomenon is not clearly visible. There are no obvious signs that the pool, surrounded by high earthen banks, might be overflowing.

So, now that the spill puzzle has been elucidated, what should we do to handle the situation ideally? Observing the huge spill, local folk such as René Uzel and Pierre Faure, not to mention the mayor Bernard Bourne, have often said: "William, maybe the captor of your spring is not adequate." In general, I've scoffed at their remarks, since the sprinkler on my lawn has always proved, to my mind, that the captor is working perfectly.

Today, I'm forced but happy to admit that their remarks are uncannily spot-on. My spring captor (built many years ago by René Uzel's father) is simply inadequate, in that it fails to handle an excessive volume of water in the pool. An ideal captor (a big concrete cistern) would be ten times the size of the present one, and it would have two outlets: a tap at the bottom for watering my lawn, and an overflow pipe at the top for calmly conveying excess water down to Gamone Creek. So, yesterday evening, I raced down to the bar in Pont-en-Royans where I can always be sure to find certain local tradesmen at the end of their working day, and I said to René Uzel, who runs his own little earth-moving business: "Come up to Gamone as soon as you've got time, and tell me how much it'll cost to rebuild your father's captor."

It's lovely to see that affairs of this kind evolve in an old-fashioned context of rural awareness and experience, in which newcomers such as me need time in order to comprehend what the native dwellers are trying to tell us. We should never believe wholeheartedly what they seem to be saying, for their conclusions are often fuzzy, nor should we ever reject entirely what they have to relate. It's fun finding the truth, which is inevitably somewhere in between.

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