Over the last 70 years, ground water in Arizona's alluvial basins was depleted by more than 74.5 million acre-feet, or approximately three times the maximum storage of Lake Powell.
Geological Survey (USGS) scientists recently released a report evaluating ground
water availability and use for all of Arizona's alluvial basins from 1940–2007.
alluvial basins, located south of the Colorado Plateau, are aquifers composed
of sand, silt and clay material that has eroded from mountains surrounding the
alluvial basins account for 95 percent of the state’s ground water use, with
ground water providing about 43 percent of the entire state’s water supply.
"Arizona is one of the fastest-growing states in the
nation, and ground water supplies will undergo increased demand as water needs
for growing population are balanced with Arizona's
agricultural sector," says USGS hydrologist Fred Tillman, who led this
water availability and use pilot study. "This USGS report is intended to
aid state and local agencies by providing them information about ground water
to help better plan for the future."
withdrawals total about 2.4 million acre-feet per year in the study area,
mainly for agriculture use and secondarily for municipal use. The primary source
of ground water recharge, or replenishment, comes from mountain runoff that
flows into the ground water basins. Ground water in these basins has been
depleted because the amount of withdrawal has outpaced aquifer recharge.
report includes updated ground water budget information for each of the 45
individual basins or management areas, as well as a new ground water-flow model
to test an approach for evaluating interconnected ground water basins. Several
indicators of ground water conditions also are analyzed, building on previous
work that resulted in the popular Arizona Groundwater Conditions Interactive
new USGS report on ground water availability and use in Arizona is a valuable compilation of
information and data," says Frank Corkhill, chief hydrologist of Arizona
Department of Water Resources. "The report provides a significant analysis
of recent water-level data and long-term trends and provides a well-balanced
assessment of the strengths and weaknesses of various methods used to estimate
ground water budget components."
The ground water
assessment and methods development effort piloted in Arizona's Southwest Alluvial Basins is being
conducted by the USGS Groundwater Resources Program. Information derived from
this study in collaboration with more than 30 regional aquifer studies, once
completed, will provide a collective assessment of America's ground water
study of Arizona's Alluvial Basins was an
important step because the ground water-flow model developed for several basins
in southern Arizona
demonstrated that it is possible to model the interconnected nature of
adjoining basins and assess how changes to ground water supplies in one area
might affect flow to or from adjacent areas.
can be found online by
following this link.
New USGS Science for Managing Arizona's Ground Water
September 26, 2011