Environmental Engineering Reference
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since that was unlikely, they needed to appropriate it from some other use. Someone noted that tamar-
isk had a reputation for consuming large amounts of water. So the mining moguls conceived the idea of
proposing to remove the tamarisk in river valleys where they wanted to tap for water and then claiming
abstraction rights to the water thereby “saved.”
Chew says that the Phelps Dodge Corporation, which wanted water from the Gila River to expand
its Morenci copper mine in Arizona, was among those that employed scientists to talk up the numbers.
The US government got involved, since metals from the mines were badly needed to build armaments
during World War II. Demonizing tamarisk became part of the war effort. In 1944, groundwater hydro-
logist Thomas Robinson and others at the US Geological Survey prepared a water report “in an effort to
determine how much water could be made available for an essential war industry by removing the salt
cedar growth from the bottom lands of Gila River.” It said the alien formed “dense jungle-like thickets
[that] thrived and spread at the expense of nearly all native plant life” and took 75 percent of the water. 12
After the war ended, the battle continued to rage against a plant that was branded by one Colorado
newspaper as “a water-gulping, fire-feeding, habitat-ruining, salt-spreading monster.” 13 A military as-
sault began, with flame-throwers and later Agent Orange deployed in the assassination of tamarisk. In
1951, the USGS's Robinson, who Chew says “built a career on tamarisk-bashing,” told the American
Geophysical Union that across the seventeen western states of the United States, the plant was wasting
water equivalent to twice the annual flow of the Colorado through the Grand Canyon. He failed to men-
tion that the cottonwood and willow trees consumed nearly as much. But no matter, Robinson's story
became the received wisdom, and it largely remains so today. 14 Joe DiTomaso, a plant ecologist at the
University of California-Davis, told me he reckons tamarisk consumes “almost twice as much as the
major cities of southern California.”
Between 2005 and 2009, Congress authorized $80 million to uproot and poison the dreaded weed.
Researching the parlous state of the Rio Grande at that time, I was repeatedly told how a stretch known
as the “forgotten river” downstream of El Paso had been dried up by tamarisk. Each scrubby indes-
tructible bush sucked up as much as a thousand quarts of water a day. The virtue of clearing tamarisk
from rivers and their banks—whether by ripping it up or dousing it with herbicides—was one of the few
things that river engineers, miners, and environmentalists all agreed on. All believed it would deliver
them more water.
But would it? What is the truth about tamarisk? Chew, who describes himself as a “reformed xeno-
phobe,” accuses his fellow scientists of peddling outdated and distorted data to “present the species as
an extreme or unnatural agent.” Certainly it is tough, he says. Certainly it is a common plant in the arid
West. By some estimates it occupies a million acres, mostly along river courses. It will survive almost
anything a desert can throw at it. But that does not make it to blame for the desert being there. Chew says
the plant is a scapegoat. The real water guzzlers are the miners, farmers, and cities. During my journey
along the Rio Grande, I had noted that the river was empty as it left El Paso, long before it reached the
tamarisk-infested “forgotten river” downstream. Perhaps cause and effect were being confused. Perhaps
tamarisk is being blamed for desert conditions simply because it can thrive there while others cannot.
The hydrology now begins to back this up. After an extensive eradication of tamarisk along the Pe-
cos River in Texas over five years from 1999, Charles Hart of Texas A&M University could find no
evidence of any greater flow in the river. 15 Early estimates reckoned that with a single plant consuming
eight hundred quarts of water a day, a dense stand of tamarisk drew down the water table by about fif-
teen feet a year, but more recent data put its drawdown potential at around three feet a year. Tamarisk
“has taken the rap unfairly,” says Chew. It is no more a water thief than cottonwood or willow or a host
of much-loved natives.
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