Chapter 6 Water Resources

Transcription

1 Chapter 6 Water Resources Elemental Geosystems 5e Robert W. Christopherson Charles E. Thomsen 1

2 Water Resources The Hydrologic Cycle Groundwater Resources Our Water Supply The Hydrologic Cycle A Hydrologic Cycle Model Surface Water 2

3 Hydrologic Cycle Model Figure 6.1 Surface Water Figure 6.2 3

4 Precipitation in North America Figure 6.4 Types of Soil Moisture Figure 6.7 4

5 Figure 6. 9 Groundwater Resources Groundwater Profile and Movement Groundwater Utilization Pollution of Groundwater Resource 5

6 Groundwater Potential Figure 6.13 Groundwater Characteristics Figure

7 Groundwater Characteristics Figure 6.14 Groundwater and Streamflow Figure

8 Our Water Supply Water Supply in the United States Water Supply in California Water Supply in Los Angeles Future Considerations 8

9 Water Withdrawal by Sector Figure 6.18 Global Water Scarcity Figure

10 California Water Supply Bsh Bwh Csa Csb D E Hot dry summers with periods of drought Winter and early spring rain Southern California 10

11 Historical Water Supply Surface water, irrigation ditches Groundwater reserves Los Angeles River, 1890 (USC Digital Archives) Los Angeles River, Griffith Park, 1900 (USC Digital Archives) Imported Water: 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 11

12 Los Angeles Aqueducts Built in 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 storage capacity of 300,560 AF. Photo courtesy of LADWP Colorado River Aqueduct Began in 1933, operational in 1941 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 AF. 775 miles of pipeline Metropolitan Water District of Southern California California Farm Water Coalition 12

13 California Aqueduct 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 Average total energy generated annually 7.6 billion Kilowatt hours Photo by William Selby (c) 2004 Andrew Alden Metropolitan Water District 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 drinking water to it s service area. 13

14 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 2,368,999 acre feet of fresh water, or approximately 772 billion gallons (MWD) City of Los Angeles LADWP sells approx 660,000 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% from MWD. Keep in mind every city has slightly different demands and dependencies. Figures from the Los Angeles Department of Water and Power (2005) 14

15 The creation of dams and alteration of natural hydrology has had a tremendous environmental impact. 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 Groundwater 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 15

16 Problems 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 16