Every minute, 10,000 gallons of water mysteriously gush out
of the desert floor at a place called Ash Meadows, an oasis that is home to 24
plant and animal species found nowhere else in the world.
A new Brigham Young University (BYU) study indicates that
the water arriving at Ash Meadows is completing a 15,000-year journey, flowing
slowly underground from what is now the Nevada Test Site.
The U.S.
government tested nuclear bombs there for four decades, and a crack in the
Earth’s crust known as the “Gravity Fault” connects its aquifer with Ash
Meadows.
It will presumably be another 15,000 years before
radioactive water surfaces at Ash Meadows, notes Stephen Nelson, a BYU geology
professor and co-author of the study. A more pressing issue for wildlife managers
at Ash Meadows is the current decline in populations of Devil’s Hole Pupfish
and three other endangered fish species.
“Since the crust in Western states is being pulled apart
east to west, it creates north-south fault lines such as this one that guides
groundwater from one geographically closed basin to another,” Nelson says.
The study appears in a recent issue ofThe Journal of
Hydrology.
Of the possible sources, only water from the Nevada Test
Site matched the profile of dissolved minerals, and had comparable hydrogen and
oxygen isotopes. Water from the Spring
Mountains near Las Vegas – previously assumed to be the
source of Ash Meadows water – carried a different isotopic signature.
The BYU researchers combed through more than 4,000 published
water samples from the region, many of those from U.S. Geological Survey wells.
From this large data set emerged 246 distinct ground water sources that they
tested against the chemical make-up of water from Ash Meadows.
“The
results are parsimonious,” Nelson says. “A majority of the water at Ash Meadows
flows from the north through fractures in the Gravity Fault.”
