Let it rain. Let it rain. Let it rain.

Very rapid housing development and 
dwindling water resources may 
soon become San Miguel's next challenge 

Conscious that water is a scarce commodity in this semi-arid part of the world, when we built our house we included three cisterns to collect rainwater from our roofs. The side-by-side cisterns are located in the back of the house, in the space created by a pretty steep slope, tucked under a large terrace.

Total capacity is approximately 325,000 liters or almost 86,000 gallons. Were we to remove the concrete cover (the terrace floor), and the two dividing walls, the combined system of cisterns would resemble a quite large swimming pool, approximately 14.3 meters long, 6.5 meters wide and 3.5 meters deep.

Annual rainfall in San Miguel is not insignificant, about 24 inches, though almost all of it comes between June and September. The rest of the year is dry as dust, which we get quite a bit of.

The two dividing walls between the three cisterns each have one large pass-through valve at the bottom that allows us to isolate the compartments for cleaning or repairs, such as we've been doing now—and which has turned out to be quite a chore.

After all that work, the cisterns were quite clean except for a sediment of very fine mud. There were no cracks on the walls or any other repairs. No mold or creepy-crawlies.

Now what we need is rain!

Félix emerging from one of the cisterns, during
long-postponed scrubing. 

Up to this year, the rainwater reserve plus a once-weekly injection of water from a community well nearby, had kept us supplied. That, plus some conservation measures, such as low-flow faucets and toilets, and a drip irrigation system in some parts of the yard.

For the past eighteen months, though, the community well system—if one could call it a "system"—has been sputtering for reasons yet unknown. We haven't received our normal share of water for at least two months, and have had to summon 10,000-liter water trucks, known here as "pipas," to make up the shortfall. Each pipa costs about fifty dollars.

The rapidly rising price of pipas, from seven hundred to a thousand pesos per trip during the past few months, suggests that scarce water is becoming a problem. Indeed, we've also noticed a growing number of pipas, usually painted blue, making deliveries around town—another bad omen.

Large as they are, the cisterns fill quite quickly when we have a heavy and consistent rain for three or four consecutive days. Except that the rainy season is not expected to start until June.

We sized the cisterns based on the square meters of roof surface of the house. Stew and I are often amazed, and pleased with ourselves, by how much planning and calculation we made during the design and construction of the house, a process that was greatly helped by one Werner Stubbs, an excellent architect and contractor well versed in "green construction," who seemed to anticipate all our preoccupations and had answers to them.

The roof over central part of the house is sloped and covered with traditional Mexican clay tiles. The water from there is captured by long gutters and directed to the two wings at at each end of the house which are flat-roofed.

At each end of the terrace are two rainwater filters  
that double as cactus planters.

From there, two four-inch downspouts, hidden in the exterior walls, direct the water to two coffin-like filtering chambers. These chambers each have fine-mesh screens and gravel through which the rainwater passes before flowing into the cisterns.

The water collects in the cisterns and is pumped by an electric pump powered by solar panels, to a pressure tank in our small basement. There, the pipes split the water supply in two—water for domestic use which is filtered, and the rest for outside faucets used for watering plants, washing cars, etc. that can be used as is.

Contrary to some people's fears, rainwater—unless you live in New Delhi or upwind from an oil refinery—is quite clean and soft. Our drinking water goes through a three-step process of filtration, including an ultraviolet light, plus a softener. The filter cartridges are changed quarterly by a local plumber.

Still, at this time of the year we're running out of water. In San Miguel, where there is rampant construction of dense housing subdivisions, some with golf courses, the municipal water supply might be strained soon if it isn't already.

Welcome to our laboratory: (l. to r.) the pressurization tank, an electric water
softener, the ultraviolet light (the long horizontal tube), and below that, a filter
to catch solids and a charcoal filter to get rid of odors. 

Visionary planning is not a strong suit of the city fathers and mothers, particularly vis-à-vis the lure of more tourists, residents and money. One does not ask too many questions during a downpour of cash.

Someone tried to sink an unlicensed well about a kilometer from us, but after a month of much banging and belching by an ancient drilling rig, the project seems abandoned. No one knows if the water authorities shut it down, the owner ran out of money or they just didn't find any water.

Apart from the malfunctioning of the community well, the problem for us might be a growing forest of trees we planted, about one hundred, that have to be watered every one or two weeks.

Solutions are not clear, apart from calling a pipa every three weeks or so. The cost is not exorbitant given that our off-the-grid house has virtually no other utility costs. Another is to explore, i.e. Google, just how much water grown evergreens need. Felix is applying about ten gallons a week each, which seems too much.

Apart from that, I can only think of prayers. Or maybe singing a few bars of Eric Clapton's catchy 1970 tune, "Let it rain." Go ahead and play it.

As I was finishing this post late yesterday, Stew came in to the office and announced it might, in fact, be starting to rain. Out the window the clouds seemed auspiciously gray and gravid with rain.

But after a few timid droplets, nothing came out of it.