San Pedro River

San Pedro River Soliloquy

It whispers, gurgles, laughs and chortles, this sliver of a creek flowing north from Mexico toward the Gila River.  On this lovely day in April, the San Pedro River still flows through the sandy banks, but within a month or so it will begin to dry up, except for isolated pools and stretches near the Mexican border.

This lovely little ribbon of water is an incredible linear oasis in the desert.  The tall cottonwoods and willows lining its banks provide habitat for 2/3 of the bird species found in the entire US.  It’s also home, at least part-time, to 80 species of mammals and 200 species of butterflies.   That incredible biodiversity draws some 4 million human visitors each year.

The small cities of Sierra Vista and Benson, near the river’s banks, are rapidly growing, as is the Fort Huachuca military installation.  All pump groundwater from the local aquifer, and there has been a long running debate about the effects of that water pumping on the flows of the river.  Numerous studies have shown that pumping groundwater in the area siphons water from the river. According to a recent post on a High Country News blog:

“Many studies since the 1980’s predict that the water table could drop so far that it would no longer support a year-round flow, killing cottonwood and willow trees and harming riparian habitat.”

Other rivers in southern Arizona have already gone dry from too much pumping.  Sierra Vista and the Fort have instituted some water conservation measures, as well as supporting various methods of recharge including creating impoundments to catch runoff from the mountains and reintroducing beavers to the river with the hopes that beaver dams will help recharge the aquifer.   But the boomtown logic of the west favors growth and get-rich-quick schemes over sustainability and livable communities.   And Benson and Sierra Vista seem to be in a race to see which can top the 100,000 population mark.

The growth of human populations in the upper San Pedro River basin seems to be  outpacing recharge efforts.   According to recent stories at EarthJustice.org (here) and the High Country News blog, the Arizona Department of Water Resources has recently approved another large subdivision in Sierra Vista, in spite of lawsuits by the Center for Biological Diversity, Huachuca Audubon Society, and even the Bureau of Land Management which manages much of the upper San Pedro.  Current water law in Arizona separates surface water (the river) from ground water (aquifer), so the ADWR apparently cannot legally restrict groundwater pumping in order to save the river, science be damned (pardon the pun).  Further legal action may be taken; hopefully it will result in a redefinition of “ground water”, so that impacts on surface water can be taken into consideration.

But the river and it’s biodiversity are blissfully unaware of the battles going on outside of its banks.  For now, it’s a lovely, lush band of greenery; a respite from the city and the desert.  On my recent walk up the river, the cottonwood trees were shedding their “cotton”, the birds were establishing territories, a solo coati almost joined me for lunch and later in the afternoon I saw 15 more, running along the top of the river bank.  The one thing I didn’t see was any fresh beaver sign.  Last year’s dam was gone, and there were no fresh cuttings or tracks.    The beaver have it tough on the San Pedro, too little water much of the year, too much during the summer.  I’m not sure how much we can count on beavers to make up for excessive water use in the area.  I hope greed doesn’t turn the last free-flowing river in the southwest into just a memory.

A longer version of this recording appears in the album, Crossroads.

See also San Pedro Autumn.

For more about the biodiversity of the San Pedro River:

Soykan et al. 2012.  Multitaxonomic diversity patterns along a desert-riparian upland gradient. PLoS ONE 7(1): e28235.

Recording notes: Recorded with a Sony PCM-M10 and Audio-Technica AT2022 with FEL SK3.5 preamp.  Recording subject to amplification and equalization.

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