Geoscience Reference
In-Depth Information
Bishop
Linyo National
Forest
395
Death Valley
National Monument
National
Forests
China Lake Naval
Weapons Center
PM-10 Violations
14
395
Possible PM-10 Violations
Edwards Air
Force Base
Air Quality Reduction
North
14
TwentyNine Palms
Marine Corps Base
San Cabinet
National Forests
San Bernardino
National Forests
10
Joshua Tree
National Monument
Los Angeles
San
Bernardino
Pacific Ocean
Figure 23.6
Air quality violations south of Owens (dry) Lake, California (after GBUAPCD, 1994).
groundwater near the surface, the precipitation of efflo-
rescent salt crusts by the discharging groundwater, a sus-
tained wind above 7 m/s, a high wind shear above a flat
unobstructed surface, a 1.5 km fetch length across the
playa and a supply of coarse sand that can abrade a stable
salt crust as it saltates. Extensive monitoring of the lake
has identified the interaction of such conditions at specific
localities in the basin where the worst emissive areas are
found. Such information has allowed mitigation measures
to be tested and designed to reduce the likelihood of dust
erosion from these surfaces (Kim, Cho and White, 2000;
Tyler
et al.
, 1997; Dahlgren, Richards and Yu, 1997).
Three dust control measures have been implemented
at Owens Lake. These are shallow flooding from perma-
nently sited outlets across the lake to maintain at least
75 % surface saturated soil, the planting of native salt-
grass using drip irrigation to maintain at least a 50 %
ground cover and the spreading of a 4 inch thick gravel
blanket (GBUAPCD, 2007). By 2006 these measures had
been employed over nearly 30 square miles of the lake
bed at a cost of $415 million (GBUAPCD, 2007). The
success of the plan is still being determined but there are
proposals to extend the mitigation measures if required.
The huge and lengthy scientific, financial and practical
efforts required to reduce dust emission from the surface
of Owens Lake are put into context by the disaster facing
the region around the Aral Sea, where at least 42 000 km
2
of potentially erodible sediment has been exposed by the
shrinking sea (Singer
et al.
, 2003). Once the fourth largest
inland sea in the world, the Aral Sea has been shrinking
