2 pages report - Cardillac Desert book

Water Cycle

Lakes

Ekman Transport/Gyres

Lake Tahoe Bathymetry

Why is lake Tahoe so clear?

Small drainage area compared to size of Lake Tahoe

low nutrient load into lake

Very deep (501 m)

Why is it important to understand geohazards?

!

Much infrastructure along the coastMuch infrastructure along the coast

Model Earthquakes - TeraShake Project

Large Historic Earthquakes, California

Lone Pine Earthquake, March 26th, 1872 M 7.6-8.0, 27 Dead, 4-5 m vertical, 10-15 m lateral

Great San Francisco Earthquake, April 18th, 1906 M 7.8, 3000+ Dead, 6 m lateral, 8.5 m lateral at depth

Fort Tejon Earthquake, January 9th, 1857 M 7.9, 2 Dead, 6 m lateral, 9 m lateral

Loma Prieta Earthquake, October 17th, 1989

aka World Series Earthquake M 6.9, 63 Dead, 4000 injured

Northridge Earthquake, January 17th, 1994

M 6.7, 72 Killed, 9000 injured, highest measured g

Future Earthquake?

San Andreas Fault Hayward Fault

M6.7+M7.8+

West Tahoe Fault

M7.3

San Jacinto Fault

M7 Wasatch Fault M7

We cannot predict earthquakes - so we develop probabilities - hazard area maps

Secchi Dish

Urbanization causes increased runoff and less lag between precipitation and discharge

Horsetail Falls, Yosemite

Meandering River with oxbow lakes

Rich soils in the river valley deposited during floods - make for great farming opportunities

(e.g., Nile)

Braided Rivers exhibit numerous channels that split off and rejoin each other to give a braided appearance. They typically carry fairly coarse- grained sediment down a fairly steep gradient. Additionally, the water discharge tends to be highly variable. Consequently, braided rivers usually exist near mountainous regions, especially those with glaciers.

TROUBLED WATERS

1901: Imperial Canal brings water from the Colorado River to the Imperial Valley.

1904: Silt blocks the Imperial Canal preventing it from supplying water to the Imperial Valley.

1905: Temporary diversion of the Colorado River, constructed to replace water from the blocked canal, is breached by floodwaters. River changes course and flows into Salton Sink.

1906: Floodwaters continue to fill Salton Sea, washing away a chain of lakes along the route and threatening Imperial Valley’s fledgling agriculture industry.

1906: The Salton Sea is recorded at – 195 feet below sea level.

1907: Floodwaters continue to fill Salton Sea until in February Southern Pacific Railroad closes the river breach.

So why hasn’t the Salton Sea dried up?

Scripps Institution of Oceanography

Scripps Institution of Oceanography

Sea level is Falling

Sea level is Falling

Dust blowing from the dry lakebed became a problem for the communities surrounding Owens Lake, and its presence eventually constituted a violation of the Federal air quality dust standard. In July 1998, the City of Los Angeles and the Great Basin Unified Air Pollution Control District entered into a historic agreement committing the Los Angeles Department of Water and Power to mitigate the dust conditions.

Salton Sea salinity is at an all time high (5.1%) and threatens the tilapia population

Important Western Fly Way

Reported Salton Sea Salinities

Future Conditions of the Salton Sea

Created in 1905 through irrigation canal failure Landlocked repository for agricultural drainage Heavily used by migratory waterfowl, including endangered species Flows are expected to decrease by as much as 50% over next 10 years as Imperial Irrigation District sells water to thirsty urban region of San Diego Salinity increasing every year

Without human intervention, sea will eventually become “hypersaline” unable to support fish, waterfowl

Salton Sea

Yes Billion

Three-salt lake

• carbonates

• chlorides

• sulfates

Mixture of table salt, baking soda, and sulfates