Are Deserts Still Drying Out Since the Ice Age?
The answer appears
to be yes, and this information could influence
hazardous waste disposal practices. USGS scientists and their university
partners have found that the sediments beneath the Nation’s southwestern
deserts have been drying out for 16,000 years, since the cold and wet
conditions of the ice age began to change to the hot and dry conditions
of today. Aided by computer models, the scientists have learned that
the drying out of these thick layers of dry sediments called the unsaturated
zone has resulted
in moisture moving upward rather than downward as expected. Normally
precipitation percolates downward and replenishes ground water. However,
the arid climate and desert plants draw moisture upward from hundreds
of feet down in the subsurface. What the scientists have learned has
implications for long-term waste disposal in the desert’s extremely
dry unsaturated zones, because it means that removal of native vegetation,
disposal of liquids, or changes to a wetter climate could potentially
allow water and contaminants to percolate downward. This understanding
of moisture movement can also be used to design better covers for desert
landfills that rely on native plants to dry out sediments. In addition,
the absence of ground-water replenishment in desert areas has important
implications for sustainability of scarce ground-water resources.
More information
Related Headlines
Toxics Program Unsaturated Zone Research
Other USGS Information on Unsaturated Zone Flow and Transport
References
-
Andraski, B.J., 1997, Soil-water
movement under natural-site and waste-site conditions--A multiple-year
field study in the Mojave
Desert, Nevada: Water Resources
Research, v. 33, no. 9, p. 1901-1916.
- Nimmo, J.R., Healy, R.W., and Stonestrom, D.A., 2003, Aquifer
recharge,
in Stewart, B.A., and Howell, T.A., eds., Encyclopedia of Water
Science: New York, Marcel Dekker, Inc., p. 22-25.
- Scanlon, B. R., Keese, Kelley, Reedy, R. C., Simunek, Jirka, and
Andraski, B. J., 2003, Variations in flow and transport in thick
desert vadose zones in response to paleoclimatic forcing (0-90
kyr)--Field measurements, modeling, and uncertainties:
Water Resources Research, vol. 39, no. 7, 1179, p. 3-1--3-17,
doi:10.1029/2002WR001604.
- Stonestrom, D.A., Prudic, D.E., Laczniak, R.J., Akstin, K.C., Boyd,
R.A., and Henkelman, K.K., 2003, Estimates of deep percolation
beneath irrigated fields, native vegetation, and the Amargosa-River
channel, Amargosa Desert, Nye County, Nevada: U.S. Geological
Survey Open-File Report 03-104, 83 p.
-
Walvoord, M.A., Phillips, F.M., Tyler, S.W., and Hartsough, P.C.,
2002, Deep
arid system hydrodynamics--2. Application to paleohydrologic reconstruction
using vadose zone profiles from the northern Mojave Desert:
Water Resources Research, v. 38, no. 12, p. 27-1 to 27-12.
-
Walvoord, M.A., Plummer, M.A., Phillips, F.M., and Wolfsberg, A.V.,
2002, Deep
system hydrodynamics--1. Equilibrium states and response times
in
thick desert vadose zones:
Water Resources Research, v. 38, no. 12, p. 44-1 to 44-15.
- Walvoord, M.A., Stonestrom, D.A., Andraski, B.J., and Striegl, R.G., 2004,
Constraining the inferred paleohydrologic evolution of a deep unsaturated
zone in the Amargosa Desert: Vadose Zone Journal, vol. 3, p. 502-512.
-
Walvoord, M.A., Stonestrom, D.A., and Phillips, F.M., 2002, From
multi-year observations to millennial inferences--Uncertainties
in paleohydrologic
reconstructions of deep unsaturated zones in the desert southwest,
U.S.A.: Eos, Transactions, American
Geophysical Union, v. 83, no. 47, Fall Meeting Supplement, Abstract
H22F-07, CD-ROM.
Back to Headlines page
|
|