1fs. Owens Lake Dust StormsStrange as it seems, one of the largest
single air pollution sources in the United States lies hundreds of miles
from heavy industry, smokestacks, or roadways clogged with automobiles.
The polluter is the nearly dry bed of Owens Lake in eastern California,
which periodically belches clouds of dust high into the atmosphere that
endanger health and cause millions of dollars of economic damage each
year.(Figure 4-3-1). Although they might seem to be natural occurrences,
these storms are the direct result of actions taken a century ago to
benefit growing populations in Southern California.The Drying of Owens
LakeOwens Lake is an ancient body of water fed from the north by the
Owens River. During glacial times thousands of years ago, the lake was
so full of water that it spilled over high passes to the south, with
some of its water reaching what is now Death Valley. As the climate
warmed and became drier, the lake became shallower and developed into a
terminal lake with no outlet. But it was still a substantial body of
water until the early 20th century, complete with steamships
transporting silver, lead, and zinc ore taken from mines in the
mountains to the east.All this changed with construction of the Los
Angeles Aqueduct in 1913. This massive water project is an engineering
marvel. Every second it moves about 10 cubic meters of water (2642
gallons) more than 200 miles southward by gravity alone, and it
generates electricity as well. But its effect on Owens Lake was anything
but benign. Within 17 years the lake was essentially dry, appearing
much as it does today (Figure 4-3-2). With this drying came huge dust
storms caused by winds picking up fine-grained material from the former
lake bed.Dust StormsThe dry lake is about 280 km2 (108 mi2), about 40
percent of which is covered by minerals left behind by evaporation of
briny water. Compared to much older natural lake beds in the West that
have had time to equilibrate with their climate, the floor of Owens Lake
is very active.When winds are strong enough, sand-sized rock fragments
bounce along the ground, breaking the surface deposits into small
particles that can be lofted high into the atmosphere. Particularly
worrisome are particles smaller than 10 µm in diameter, so-called PM10
particles. These travel great distances and are a serious health hazard
for animals and people unlucky enough to be exposed to them (see Chapter
14 for more information about PM10 particles).The geography of the
Owens Valley means strong winds and associated dust storms are common.
It was originally believed that the dust storms were caused by winds
blowing across the Sierra Nevada Mountains and down into the valley from
the west. But more recent research has revealed that strong westerly
winds are rare, and most storms have winds that blow along the valley
axis, from either the south or north. High winds arise from several
mechanisms, including the passage of cold fronts, downward momentum
transfer from fast-moving air high in the atmosphere, and channeling of
air through valley side-walls. Dust storms can occur any time of year,
but are most common in the spring.The net effect is that the Owens Lake
bed can produce very large quantities of dust, by one estimate about
half a million metric tons of dust every year (about 550 million U.S.
tons). This amounts to 6 percent of the total U.S. production from one
very small area. Communities in the surrounding area within the valley
exceed federal air quality standards for particulates 48 times per year
on average. Dust reaches high elevations in surrounding mountains, where
it has the potential to damage sensitive tree species. In some cases
dust storms affect visibility as much as 250 km (150 mi) away. Dust is
also blown into nearby protected wilderness areas that have minimum
visibility requirements set by federal law.RemediationThere has never
been any doubt about the origin of this dust or the responsibility of
the city of Los Angeles in its production. Following an historic
agreement reached in the late 1990s, the city has been charged with
making efforts to control Owens Lake dust. It has employed several
methods, the most successful of which is to simply pump water back into
the lake and thereby reduce the amount of dry sediment exposed to
scouring winds. There is no doubt these efforts have had great effect,
with measurements typically 10 times lower than before. However, dust
levels remain 10 times higher than federal standards and are higher than
similar dry locations elsewhere. At present the city of Los Angeles
claims it has done what was promised, while other stakeholders say more
must be done. As so often happens with issues related to water, the
matter is now in federal court.FIGURE 4-3-1 Owens Lake, California. As
seen in the (a) map and (b) satellite image Owens Lake lies between the
Sierra Nevada and Inyo Mountains....FIGURE 4-3-2 Owens Lake Today. The
mostly dry lake viewed from the south....What atmospheric factors
contribute to dust storms in the Owens Valley? Get solution
2fs. Owens Lake Dust StormsStrange as it seems, one of the largest single air pollution sources in the United States lies hundreds of miles from heavy industry, smokestacks, or roadways clogged with automobiles. The polluter is the nearly dry bed of Owens Lake in eastern California, which periodically belches clouds of dust high into the atmosphere that endanger health and cause millions of dollars of economic damage each year.(Figure 4-3-1). Although they might seem to be natural occurrences, these storms are the direct result of actions taken a century ago to benefit growing populations in Southern California.The Drying of Owens LakeOwens Lake is an ancient body of water fed from the north by the Owens River. During glacial times thousands of years ago, the lake was so full of water that it spilled over high passes to the south, with some of its water reaching what is now Death Valley. As the climate warmed and became drier, the lake became shallower and developed into a terminal lake with no outlet. But it was still a substantial body of water until the early 20th century, complete with steamships transporting silver, lead, and zinc ore taken from mines in the mountains to the east.All this changed with construction of the Los Angeles Aqueduct in 1913. This massive water project is an engineering marvel. Every second it moves about 10 cubic meters of water (2642 gallons) more than 200 miles southward by gravity alone, and it generates electricity as well. But its effect on Owens Lake was anything but benign. Within 17 years the lake was essentially dry, appearing much as it does today (Figure 4-3-2). With this drying came huge dust storms caused by winds picking up fine-grained material from the former lake bed.Dust StormsThe dry lake is about 280 km2 (108 mi2), about 40 percent of which is covered by minerals left behind by evaporation of briny water. Compared to much older natural lake beds in the West that have had time to equilibrate with their climate, the floor of Owens Lake is very active.When winds are strong enough, sand-sized rock fragments bounce along the ground, breaking the surface deposits into small particles that can be lofted high into the atmosphere. Particularly worrisome are particles smaller than 10 µm in diameter, so-called PM10 particles. These travel great distances and are a serious health hazard for animals and people unlucky enough to be exposed to them (see Chapter 14 for more information about PM10 particles).The geography of the Owens Valley means strong winds and associated dust storms are common. It was originally believed that the dust storms were caused by winds blowing across the Sierra Nevada Mountains and down into the valley from the west. But more recent research has revealed that strong westerly winds are rare, and most storms have winds that blow along the valley axis, from either the south or north. High winds arise from several mechanisms, including the passage of cold fronts, downward momentum transfer from fast-moving air high in the atmosphere, and channeling of air through valley side-walls. Dust storms can occur any time of year, but are most common in the spring.The net effect is that the Owens Lake bed can produce very large quantities of dust, by one estimate about half a million metric tons of dust every year (about 550 million U.S. tons). This amounts to 6 percent of the total U.S. production from one very small area. Communities in the surrounding area within the valley exceed federal air quality standards for particulates 48 times per year on average. Dust reaches high elevations in surrounding mountains, where it has the potential to damage sensitive tree species. In some cases dust storms affect visibility as much as 250 km (150 mi) away. Dust is also blown into nearby protected wilderness areas that have minimum visibility requirements set by federal law.RemediationThere has never been any doubt about the origin of this dust or the responsibility of the city of Los Angeles in its production. Following an historic agreement reached in the late 1990s, the city has been charged with making efforts to control Owens Lake dust. It has employed several methods, the most successful of which is to simply pump water back into the lake and thereby reduce the amount of dry sediment exposed to scouring winds. There is no doubt these efforts have had great effect, with measurements typically 10 times lower than before. However, dust levels remain 10 times higher than federal standards and are higher than similar dry locations elsewhere. At present the city of Los Angeles claims it has done what was promised, while other stakeholders say more must be done. As so often happens with issues related to water, the matter is now in federal court.FIGURE 4-3-1 Owens Lake, California. As seen in the (a) map and (b) satellite image Owens Lake lies between the Sierra Nevada and Inyo Mountains....FIGURE 4-3-2 Owens Lake Today. The mostly dry lake viewed from the south....If you were the federal judge hearing the case, what factors would you consider in deciding if Los Angeles has done enough to reduce dust? Get solution
2fs. Owens Lake Dust StormsStrange as it seems, one of the largest single air pollution sources in the United States lies hundreds of miles from heavy industry, smokestacks, or roadways clogged with automobiles. The polluter is the nearly dry bed of Owens Lake in eastern California, which periodically belches clouds of dust high into the atmosphere that endanger health and cause millions of dollars of economic damage each year.(Figure 4-3-1). Although they might seem to be natural occurrences, these storms are the direct result of actions taken a century ago to benefit growing populations in Southern California.The Drying of Owens LakeOwens Lake is an ancient body of water fed from the north by the Owens River. During glacial times thousands of years ago, the lake was so full of water that it spilled over high passes to the south, with some of its water reaching what is now Death Valley. As the climate warmed and became drier, the lake became shallower and developed into a terminal lake with no outlet. But it was still a substantial body of water until the early 20th century, complete with steamships transporting silver, lead, and zinc ore taken from mines in the mountains to the east.All this changed with construction of the Los Angeles Aqueduct in 1913. This massive water project is an engineering marvel. Every second it moves about 10 cubic meters of water (2642 gallons) more than 200 miles southward by gravity alone, and it generates electricity as well. But its effect on Owens Lake was anything but benign. Within 17 years the lake was essentially dry, appearing much as it does today (Figure 4-3-2). With this drying came huge dust storms caused by winds picking up fine-grained material from the former lake bed.Dust StormsThe dry lake is about 280 km2 (108 mi2), about 40 percent of which is covered by minerals left behind by evaporation of briny water. Compared to much older natural lake beds in the West that have had time to equilibrate with their climate, the floor of Owens Lake is very active.When winds are strong enough, sand-sized rock fragments bounce along the ground, breaking the surface deposits into small particles that can be lofted high into the atmosphere. Particularly worrisome are particles smaller than 10 µm in diameter, so-called PM10 particles. These travel great distances and are a serious health hazard for animals and people unlucky enough to be exposed to them (see Chapter 14 for more information about PM10 particles).The geography of the Owens Valley means strong winds and associated dust storms are common. It was originally believed that the dust storms were caused by winds blowing across the Sierra Nevada Mountains and down into the valley from the west. But more recent research has revealed that strong westerly winds are rare, and most storms have winds that blow along the valley axis, from either the south or north. High winds arise from several mechanisms, including the passage of cold fronts, downward momentum transfer from fast-moving air high in the atmosphere, and channeling of air through valley side-walls. Dust storms can occur any time of year, but are most common in the spring.The net effect is that the Owens Lake bed can produce very large quantities of dust, by one estimate about half a million metric tons of dust every year (about 550 million U.S. tons). This amounts to 6 percent of the total U.S. production from one very small area. Communities in the surrounding area within the valley exceed federal air quality standards for particulates 48 times per year on average. Dust reaches high elevations in surrounding mountains, where it has the potential to damage sensitive tree species. In some cases dust storms affect visibility as much as 250 km (150 mi) away. Dust is also blown into nearby protected wilderness areas that have minimum visibility requirements set by federal law.RemediationThere has never been any doubt about the origin of this dust or the responsibility of the city of Los Angeles in its production. Following an historic agreement reached in the late 1990s, the city has been charged with making efforts to control Owens Lake dust. It has employed several methods, the most successful of which is to simply pump water back into the lake and thereby reduce the amount of dry sediment exposed to scouring winds. There is no doubt these efforts have had great effect, with measurements typically 10 times lower than before. However, dust levels remain 10 times higher than federal standards and are higher than similar dry locations elsewhere. At present the city of Los Angeles claims it has done what was promised, while other stakeholders say more must be done. As so often happens with issues related to water, the matter is now in federal court.FIGURE 4-3-1 Owens Lake, California. As seen in the (a) map and (b) satellite image Owens Lake lies between the Sierra Nevada and Inyo Mountains....FIGURE 4-3-2 Owens Lake Today. The mostly dry lake viewed from the south....If you were the federal judge hearing the case, what factors would you consider in deciding if Los Angeles has done enough to reduce dust? Get solution
