U.S.
Department of Agriculture (USDA) scientists are helping meet the water demands
of a riparian desert region that is home to a national conservation area and a
thriving military base.
Agricultural
Research Service (ARS) hydraulic engineer Dave Goodrich and hydrologist Russ
Scott have been part of Arizona's
Upper San Pedro Partnership (USPP) – a mix of 21 federal, state and local
groups managing the region's water-supply needs – since the association started
in 1998. ARS is USDA's chief intramural scientific research agency, and this
work supports the USDA priority of responding to climate change.
Fort Huachuca, which is
the primary economic engine in the upper San
Pedro River
valley, draws its water from the aquifer that sustains the desert river, but
this ground water is being depleted more rapidly than it is replenished. In
2004, Congress directed the Department of the Interior to work with the
Department of Defense, USDA and the USPP to develop water-use management and
conservation measures that would restore and maintain water supplies in the
upper San Pedro watershed.
Goodrich
and Scott both work at the ARS Southwest Watershed
Research Center
in Tucson, Ariz. The scientists are studying how much
water is used by riparian vegetation, and evaluating how storm water runoff
from urban development affects ground water reserves.
As part of
this work, Goodrich and others measured storm water runoff from undeveloped
land at the edge of Fort
Huachuca and from a newly
developed area just outside the military installation. They found that a third
of the runoff from the developed site resulted just from the compaction from
the surface soils during construction – and not from the installation of
impervious barriers, as they had expected.
Meanwhile,
Scott and his colleagues found that mesquite woodlands use much more water than
cottonwood and willow trees that grow along the riverbanks. He used this
finding to develop a GIS-based riparian evaporation and transpiration tool that
regional land managers can use to estimate water savings by replacing mesquite
with native desert grasses.
