Dams

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Dams
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Dams
Enhanced economic prosperity Public
health Agriculture
Altered natural environments Reduced
streamflows Water quality degradation Fish and
wildlife
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Ancient Cultures
Earth, rocks, logs
Flood control and irrigation
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Dams
Flood control Irrigation Redistribution Recreation
Navigation Electricity
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Dam Basics
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Components
Face exposed surface of the structure Abutments
sides of the dam Crest top of the dam Toe
natural ground surface Outlet opening to
discharge water Spillway chute to allow excess
water flow
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Components
Face Abutments Crest Toe Outlet spillway
upriver
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Types of Dams
Gravity Concrete Concrete Arch Earthen
Embankment
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Types of Dams
Gravity Concrete Concrete Arch Earthen
Embankment
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Gravity Concrete
Concrete Arch
(mass)
Earthen Embankment
More than 50 Compacted earth
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Dead Storage Active Storage Flood Pool
Storage Surcharge (temp. flood pool)
Dam Storage
Total capacity
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Capacity
Total Capacity all storage space Live Capacity
total that can be released by gravity
(total dead) Freeboard difference in
elevation between the dam
crest and the maximum water
surface
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Major U.S. Dams
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Examples
Hoover Dam Grand Cooley Dam Kingsley Dam
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Hoover Dam
(Boulder Canyon Dam)
One of 11 major dams Completed 1935 165
million Concrete Gravity Arch Black Creek Canyon
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Hoover Dam
726 feet high 1244 ft length 660 feet thick at
base 45 feet thick at crest
Lake Mead
Crest
Base
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Lake Mead
Elwood Mead
10.5 trillion gallons 581 feet deep 110 miles long
Lake Mead
2000 megawatts
Irrigation Hydroelectric power Municipal
use Recreation Fish and wildlife
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Grand Cooley Dam
Concrete Gravity Dam Columbia River in Central
Washington Constructed 1933-1941
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Grand Cooley Dam
Largest concrete Structure in the U.S.
550 feet high 5223 feet long 500 feet wide at
base 30 feet wide at crest
Hoover
1244 ft length 660 feet thick at base 45 feet
thick at crest
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Kingsley Dam
Earthen Dam Ogallala Nebraska North Platte
River Constructed 1936-41
Steel and Clay core Sand, gravel, soil
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Kingsley Dam
Width 3.5 miles Height 162 feet Base width
1100 feet Crest width 28 feet
Grand Cooley
Hoover
5223 feet long 500 feet wide at base 30 feet wide
at crest
1244 ft length 660 feet thick at base 45 feet
thick at crest
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Dates
Hoover Dam
1931-1935
Grand Cooley Dam
1933-1941
1936-1941
Kingsley Dam
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The Great Depression
1929 - 1941

• Over 25 unemployment
• Manufacturing down 50

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Impacts of Dams
Change in river character
Temperature Stress Rigid barriers to migratory
fish Water release changes sediments, O2
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Sedimentation
Still water behind the dam deposits
sediments Clear water released, scouring the
riverbed downstream Further downstream, new
sediment load deposited creating sandbars and
islands slowing the river.
Reservoir capacity reduced
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The Three Gorges Dam
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Concrete Gravity Length 1.2 miles Height
608 ft
The Three Gorges Dam Yangtze River
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Yangtze River Watershed
Houses 1/3 Chinas population Supplies ½ Chinas
food
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The Reservoir
574 feet deep 373 miles long Filled by 2009
Equal in length to Lake Superior
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Benefits
Hydroelectric Power
85 billion kilowatts per year 10 of future
energy needs Clean energy alternative
Flood Protection
300,000 deaths by flooding
Navigation
Commercial shipping to central China
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Costs
Water stagnation in Reservoir
Increased temperatures Increased salinity Human
wastes Sedimentation and nutrients
Cultural Consequences
Relocation of up to 2 million people Breakup of
traditional rural social system
Adaptation to urban lifestyles, industry
Farmlands and burial grounds flooded Importation
of food
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Rodman Dam
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7,200-foot-long Earthen Dam
completed in 1968
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Cross-Florida Barge Canal
Philip II of Spain in 1567 Funded first in
1935 Stopped in 1936 Reauthorized in
1942 Construction resumed 1964 Stopped in
1971 Cancelled in 1991
Nuclear power
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Ocklawaha River
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Rodman Reservoir
9,600 acres 15 miles long 2 miles wide
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River Restoration
Migratory fish blocked from the river
The floodplain and adjacent woodlands are a rare
land-use classification of sub-tropical hardwood
forest
nutrient enriched impoundment, seasonally choked
by exotic weeds, lined with stumps of the remnant
bottomland hardwood forest
Between 1985 and 2000, at least three major fish
kills have occurred.
20 natural springs submerged by the reservoir
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River Restoration
Rodman Reservoir is a viable and complex
ecosystem that supports a wide variety of native
plants and wildlife, including many endangered
species. The water quality of Rodman Reservoir
is good and is one of the few major sources of
uncontaminated water entering the St. Johns
River. Rodman Reservoir is consistently listed
by major fishing magazines as one of the ten best
bass lakes in the United States.