Dams

Enhanced economic prosperityPublic healthAgriculture

Altered natural environmentsReduced streamflowsWater quality degradationFish and wildlife

Dams

Ancient Cultures

Earth, rocks, logs

Flood control and irrigation

Dams

Flood controlIrrigationRedistributionRecreationNavigationElectricity

Dam Basics

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

Components

FaceAbutmentsCrestToeOutletspillway

upriver

Types of Dams

Gravity Concrete

Concrete Arch

Earthen Embankment

Gravity Concrete

Concrete Arch

Earthen Embankment

Types of Dams

More than 50% Compacted earth

Gravity ConcreteConcrete Arch

Earthen Embankment

(mass)

Dam Storage

Dead Storage

Active Storage

Flood Pool Storage

Surcharge (temp. flood pool)

Totalcapacity

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

Major U.S. Dams

Examples

Hoover Dam

Grand Cooley Dam

Kingsley Dam

Hoover Dam

One of 11 major damsCompleted 1935$165 millionConcrete Gravity ArchBlack Creek Canyon

(Boulder Canyon Dam)

Hoover Dam

726 feet high

1244 ft length

660 feet thick at base

45 feet thick at crest

Lake Mead

Base

Crest

Lake Mead

IrrigationHydroelectric powerMunicipal useRecreationFish and wildlife

Lake Mead

Elwood Mead

10.5 trillion gallons581 feet deep110 miles long

2000 megawatts

Grand Cooley Dam

Concrete Gravity DamColumbia River in Central WashingtonConstructed 1933-1941

Grand Cooley Dam

Largest concreteStructure in the U.S.

550 feet high5223 feet long500 feet wide at base30 feet wide at crest

1244 ft length660 feet thick at base45 feet thick at crest

Hoover

Kingsley Dam

Earthen Dam Ogallala NebraskaNorth Platte RiverConstructed 1936-41

Steel and Clay coreSand, gravel, soil

Kingsley Dam

Width = 3.5 milesHeight = 162 feetBase width = 1100 feetCrest width = 28 feet

5223 feet long500 feet wide at base30 feet wide at crest

1244 ft length660 feet thick at base45 feet thick at crest

HooverGrand Cooley

Dates

Hoover Dam

Grand Cooley Dam

Kingsley Dam 1936-1941

1933-1941

1931-1935

The Great Depression

1929 - 1941

Over 25% unemploymentManufacturing down 50%

Impacts of Dams

Change in river character

Temperature StressRigid barriers to migratory fishWater release changes – sediments, O2

Sedimentation

Still water behind the damdeposits sediments

Clear water released, scouringthe riverbed downstream

Further downstream, new sediment load deposited creatingsandbars and islands slowing the river.

Reservoir capacity reduced

The Three Gorges Dam

The Three Gorges Dam Yangtze River

Concrete Gravity

Length = 1.2 miles

Height = 608 ft

Yangtze River Watershed

Houses 1/3 China’s populationSupplies ½ China’s food

The Reservoir

574 feet deep

373 miles long

Filled by 2009

Equal in length toLake Superior

Benefits

Hydroelectric Power

85 billion kilowatts per year10% of future energy needsClean energy alternative

Flood Protection300,000 deaths by flooding

NavigationCommercial shipping to central China

Costs

Water stagnation in Reservoir

Increased temperaturesIncreased salinityHuman wastesSedimentation and nutrients

Cultural ConsequencesRelocation of up to 2 million peopleBreakup of traditional rural social system Adaptation to urban lifestyles, industry Farmlands and burial grounds floodedImportation of food

Rodman Dam

7,200-foot-longEarthen Dam

completed in 1968

Cross-FloridaBarge Canal

Philip II of Spain in 1567Funded first in 1935Stopped in 1936Reauthorized in 1942Construction resumed 1964Stopped in 1971Cancelled in 1991

Nuclear power

Ocklawaha River

Rodman Reservoir

9,600 acres15 miles long 2 miles wide

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.

River Restoration

20 natural springs submerged by the reservoir

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.