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Chapter 6Water Resources

Elemental Geosystems 5e

Robert W. ChristophersonCharles E. Thomsen

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Water ResourcesThe Hydrologic Cycle

Groundwater Resources

Our Water Supply

The Hydrologic CycleA Hydrologic Cycle Model

Surface Water

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Hydrologic Cycle Model

Figure 6.1

Surface Water

Figure 6.2

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Precipitation in North America

Figure 6.4

Types of Soil Moisture

Figure 6.7

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Figure 6. 9

Groundwater ResourcesGroundwater Profile and Movement

Groundwater Utilization

Pollution of Groundwater Resource

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Groundwater Potential

Figure 6.13

Groundwater Characteristics

Figure 6.14

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Groundwater Characteristics

Figure 6.14

Groundwater and Streamflow

Figure 6.16

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Our Water SupplyWater Supply in the United States

Water Supply in California

Water Supply in Los Angeles

Future Considerations

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Water Withdrawal by Sector

Figure 6.18

Global Water Scarcity

Figure 6.20

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• Hot dry summers with periods of d ht

Bsh

California Water Supply

drought

• Winter and early spring rainCsaCsbDE

Bwh

Southern California

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• Surface water, irrigation ditches • Groundwater reserves

Historical Water Supply

• Groundwater reserves

Los Angeles River, Griffith Park, 1900 (USC Digital Archives)Los Angeles River, 1890 (USC Digital Archives)

Imported Water:

• Los Angeles Aqueducts

Water Supply Today

Los Angeles Aqueducts

• Colorado River Aqueduct

• California Aqueduct (San Francisco Bay/Sacramento-San Joaquin Delta)

• Local Sources (groundwater basins)

• Limited amounts of treated wastewater and locally captured surface runoff in some areas

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Los Angeles AqueductsLos Angeles Aqueducts

Water Supply Today

• Built in 1913

• 340 miles from the Mono Basin through Owens Valley to Los Angeles

• Water is conveyed by gravity alone

• There are seven reservoirs in the system with a combined storagesystem with a combined storage capacity of 300,560 AF.

Photo courtesy of LADWP

Colorado River AqueductColorado River Aqueduct

• Began in 1933, operational in

Water Supply Today

g , p1941

• Covers 242 miles from Lake Havasu to Lake Mathews

• Can deliver up to 1.3 million acre feet per year

• There are 9 reservoirs with a storage capacity of 1 092 000

Metropolitan Water District of Southern California

storage capacity of 1, 092, 000 AF.

• 775 miles of pipeline

California Farm Water Coalition

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California AqueductCalifornia Aqueduct

C l t d i th 1970’ t

Water Supply Today

• Completed in the 1970’s to bring water to the San Fernando Valley

• Begins at Lake Oroville ends in Los Angeles County

• Includes 21 lakes and reservoirs, 661 miles of pipeline

Photo by William Selby

• Average total energy generated annually 7.6 billion Kilowatt hours

(c) 2004 Andrew Alden

Metropolitan Water DistrictMetropolitan Water District

Water Supply Today

• Public agency formed in 1928 by a vote of electorates from 13 Southern California cities.

• 26 member cities and water districts that provide water to 18 million people

• Goal is to provide adequate and reliable supplies of drinkingreliable supplies of drinking water to it’s service area.

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Water Supply Today

One acre/foot of water serves the needs of five Los Angeles residents

Between 2000 and 2003 Los Angeles County gained 500,000 new residents (Public Policy Institute of California)

In 2003 MWD sold 2 368 999In 2003 MWD sold 2,368,999 acre feet of fresh water, or approximately 772 billiongallons (MWD)

• LADWP sells approx 660,000

City of Los AngelesCity of Los Angeles

Water Supply Today

pp ,acre/feet of fresh water each year. One Acre/foot is about 326,000 gallons (215,160,000,000 gallons)

• On average, the city has imported about 65% of it’s water from the Los Angeles Aqueduct, 15% from local groundwater reserves, and 20%

Figures from the Los Angeles Department of Water and Power (2005)

from MWD.

• Keep in mind every city has slightly different demands and dependencies.

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The creation of dams and alteration of natural hydrology has had a tremendous environmental impact.

Water Supply Today

• Alteration of natural hydrological processes (ex. Groundwater recharge, stream flow, etc.)

• Alteration of vegetation along riverbed

• Increased use of irrigation in places where there was previously no need

• The depletion of riverbed gravels reduces habitat for many fish that spawn in the gravelly river bottom, and for invertebrates such as insects, mollusks and crustaceans

• Decline in fish abundance and diversity

• Increase in invasive species

• Decline in habitat available for migratory bird species

GroundwaterGroundwater

Water Supply Today

Water found subsurface stored in:

Aquifers (confined or unconfined)

Permeable rock layers

Unconsolidated Sediments

Soil moisture

• San Fernando Valley

Groundwater found 6 - 57 meters below the surface

Great variability, however all measurements are trending to an increasing depth to groundwater

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ProblemsProblems

Water Supply Today

• Subsidence

• Water and oil extraction from compressible sedimentary layers

• SFV - subsidence occurring 6 -80mm per year

• Salt water intrusion (not a SFV issue)

• Lowered water tables

• Sea level rise

• Pollution