When is 2 cubic feet per second (cfs) big?
In the Sonoran desert, on the San Pedro River,
just before the summer monsoons start.
Prior to the 1960s the river hardly ever dropped lower than that point. Compare that to this past decade where a river flow of under 2 cfs has become the norm.
What’s the cause?
Groundwater is being depleted in the underlying aquifer as a result of water supply pumping in the nearby town of Sierra Vista.
That steals the river’s vital baseflow.
The monsoons still reliably put water in the river, but even that seems to have changed. The norm from 1945 to 1970 was for river flow to peak in August at around 200 cfs. Over the most recent 25 years (1985-2010) the summer peak has dropped to 40 percent of that total.
At stake is one of the deserts most unique ecosystems – a perennially flowing riparian corridor – which from the top of the Huachuca Mountains, when you look down, you can see it like a thread thin line running from south to north across the desert floor. Up close it is a shaded oasis of running water and other worldly Cottonwood tree stands with leaves of shimmering green (in the summer) or brilliant yellow in the fall and which greets you like a sight for sore eyes among the endless rolling plain of heated up cactus that surround it and threaten, should the water someday disappear, to overtake it and turn it to sand.
|Photo Source: Friends of the San Pedro River|
As for now the river still flows –
Not as perennial as it once was, but not yet a wash either:
Somedays you enjoy what you have and forget about the future.