Saturday, March 11, 2006

Rain in the Desert

It's raining.

Maybe that's not news where you are, but here in Phoenix, where it's been 143 days since we last had a measurable rainfall, it's big news. The last time we (officially) had water fall from the sky was October 18, 2005 -- and that was just a trace. The forecast for today is about 0.75 inch -- and that hasn't happened here since August 2, 2005, when we got 0.59 of an inch of rain. Better still, it is snowing in the mountains to the north of us, where, last week, a survey of the sites used to measure snowpack -- which is where our water really comes from -- found no snow at all at 57 of the 61 sites.

OK, so, it's a desert -- and a principal (if not the ) defining characteristic of a desert is the lack of water. That's no surprise. Yet even the driest of deserts get some rainfall. It's almost like adding insult to injury when a desert experiences a drought -- but that's what's happening here right now. The rain that's falling today will knock some of the crud out of the air, and cut the dust (and make the windshields of cars parked outside really muddy); and it will perk up some of the vegetation -- there's going to be an explosion of weeds real soon! -- but it doesn't add any water to the reservoirs that we rely on for our needs. And, while some south-faciong mountain slopes might get as much as 30 inches of snow, the overall forecast is for 5 to 8 inches above 6,000 feet -- maybe a foot in some places. Since that's only about 10% of the "normal" snowpack, this is not a "drought-breaker" by any stretch of the imagination. Hopefully, the moisture that is falling will ease the dry conditions that threaten to make this summer a form of "hell" for firefighters in the forests -- but quite often the result of a rainfall and snowfall of the type that is happening right now is to encourage an explosive undergrowth that, when the dry summer arrives, will die, and make it even easier for wildfires to start and to spread. Not much of a silver lining to these dark clouds right now...

Why dwell on this? (Which is to say, why blog about this?) Perhaps it is because the rain brings on a pensive side; and the sound of rain hitting the roof makes us think about water, and the drought here in the desert.

I found myself thinking earlier today about the way that any population is affected by the resources needed to sustain life, and how the limits to just one factor affect the "carrying capacity" -- the ability of a region to support a given population -- for the geographical area in question. Here in the desert, the carrying capacity is directly linked to the water supply -- or lack thereof. The system of reservoirs, canals, and wells tapping groundwater supplies has enhanced the carrying capacity by allowing the use of stored water -- or, in the case of the Central Arizona Project, to bring water from the Colorado River to the central counties of Maricopa and Pima (home to the Phoenix metor area cluster of cities, and to Tucson, the "other" big city in the state of Arizona) to supplement local water supplies.

Once upon a time, there was a civilization that lived in the Phoenix area, known now as the "Hohokam" -- we have no idea how they called themselves. They vanished without a trace about 500 years ago. Theirs was, for a time, an apparently successful civilization here in the desert. Indeed, a number of the canals that deliver water here today are built along the routes used by the irrigators of the Hohokam people; and other traces of their irrigation system remain to this day. But of the people, nothing.

We tend to think that, because our technology is better, we are somehow immune from the pressures that ultimately forced the Hohokam civilization here to collapse. It may even make us think we are better, smarter, than they were. But drought was, apparently, the cause of their downfall -- and could be ours, as well... And drought, of course, is solely in the hands of God.