Encyclopedia of Global Resources part 72 pptx

Regarding future production, Kazakhstan has the largest reserves of chromium in the world 26 per-cent of the world total, far outpacing South Africa 15 percent of world total and India 3

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Kazakhstan will continue to be a major player in the

global oil market Perhaps the crowning illustration of

oil’s significance to the Kazakh economy is President

Nursultan Nazarbayev’s ambitious “Kazakhstan 2030”

campaign This directive seeks to vault Kazakhstan

into the world’s fifty most economically developed

counties Perhaps not coincidentally, Kazakhstan’s oil

production is expected to peak in 2030

Natural Gas

While not nearly as significant to Kazakhstan’s global

resources as its oil deposits, natural gas is also an

im-portant resource, particularly in satisfying local

de-mand Kazakhstan’s production of natural gas (nearly

28 trillion cubic meters in 2007) pales in comparison to

neighboring Russia (654 trillion cubic meters),

Turk-menistan (69 trillion cubic meters), and Uzbekistan

(65 trillion cubic meters) Production is significant,

however, placing Kazakhstan twenty-fifth among

nat-ural-gas-producing countries, between Pakistan and

Venezuela While much of the natural gas production

fulfills domestic consumption, Kazakhstan does

ex-port more than 8 trillion cubic meters, ranking it

twenty-third in the world between Brunei and the

United Arab Emirates Kazakhstan’s importance to the

global economy with respect to natural gas, however,

stems from its substantial anticipated future

produc-tion Its natural gas reserves, in 2008, estimated to be

2.8 trillion cubic meters (1.6 percent of the world

to-tal), rank Kazakhstan eleventh in the world Because

Kazakhstan consumes slightly more natural gas than

it produces (and also exports large amounts), it

im-ports nearly 11 billion cubic meters from neighboring

Uzbekistan Kazakhstan’s large area and inadequate

internal natural gas transport infrastructure

necessi-tate this import from Uzbekistan to serve the

south-ern industrial and urban centers of Shymkent and

Alma-Ata Plans have been introduced to construct

a gas pipeline linking Kazakhstan’s gas fields with

China’s western province of Xinjiang

Coal

Kazakhstan is a major producer of coal and possesses

large coal reserves Kazakhstan ranks as the world’s

tenth largest coal producer Estimates indicate that its

coal reserves rank Kazakhstan eighth in the world

While domestic coal consumption of 78 short tons (in

2006) makes Kazakhstan a major consumer, the

re-maining 28 tons of coal it produces are exported

Kazakhstan was an important coal producer for the

Soviet Union, though production declined after the country gained independence However, production has risen from its 1999 low More than one-half of Kazakhstan’s Soviet-era subsurface coal mines have closed, falling victim to restructuring difficulties, nu-merous fatal mine accidents, and difficulty in attract-ing foreign investment Coal is an important energy source within Kazakhstan, as coal-powered plants produce 80 percent of the country’s electricity The country’s coalfields, located primarily in the central Qaraghandy region, are somewhat unique in the amount of coal-bed methane emitted In fact, Kazakh-stan is one of the only countries that actively harness this gas for energy purposes

Uranium Kazakhstan’s uranium-related history includes its pri-macy as a source of the mineral for the Soviet Union and as the home of the Soviet nuclear weapons testing ground at the Polygon site near the northeastern city

of Semey Given the global concern over the burning

of fossil fuels, greenhouse-gas emissions, and contri-butions to climate change and global warming, ura-nium is poised to become an increasingly important energy source in future decades, particularly as global electricity consumption is expected to double Fur-thermore, more than thirty nuclear reactors are being built around the world, with an additional several hundred in advanced planning stages As a result, Kazakhstan is well placed to capitalize on current and future demand, as it is the world’s third largest ura-nium producer, behind Canada and Australia, and is home to the world’s second largest uranium reserves, behind only Australia Estimates put Kazakhstan’s uranium endowment at 17 percent of the world’s to-tal Kazakhstan’s proximate location to the world’s two most populous countries is also seen as an impor-tant aspect of its future uranium production and export Increases in nuclear power in China and In-dia are viewed as important markets for Kazakhstan’s uranium Unique features of Kazakhstan’s uranium stocks include accessibility, high quality, and ease of extraction By using the in situ leaching method, in which water and sulfuric acid free the mineral from surrounding rock, Kazakhstan is able to extract ura-nium at a relatively low cost The arrest of Mukhtar Dzhakishev, former chief executive officer of the na-tional uranium company Kazatomprom, is widely believed to be politically motivated This arrest, and others like it, illustrates one aspect of the risky

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ronment associated with foreign investment in

Ka-zakhstan’s mining sector

Chromium

Taking into account both current production and

estimated reserves, Kazakhstan may be the global

economy’s most important source of chromium

Al-ternatively referred to as chrome ore or chromite, the

mineral has a unique blend of corrosion resistance,

hardness, and bright finish, which make it an

indis-pensable input for jet-engine turbine blades,

fuel-efficient engine, and, most important for the global

economy, stainless steel Kazakhstan produces 17

per-cent of the world’s chromium, second only to South

Africa Regarding future production, Kazakhstan has

the largest reserves of chromium in the world (26

per-cent of the world total), far outpacing South Africa

(15 percent of world total) and India (3 percent of

world total) Global demand for chromium largely

mirrors that for stainless steel, the most important

end use of chromium In fact, there is not a substitute

for chromium in the production of stainless steel, a

fact that solidifies Kazakhstan’s importance in the global chromium market Kazkhrom, a chromium ex-traction company, nearly one-third of which is owned

by the Kazakhstan government, is the world’s second-largest chromium producer About one-half of pro-duction is exported; the other half is used in Kazakh-stan’s sizable steel industry Quantifying chromium’s contribution to the Kazakhstan economy is difficult as the mineral is not an openly traded commodity and exchange details are not made public Global short-ages of chromium have, however, resulted from de-mand greatly outstripping supply As a result, com-modity prices were estimated to have doubled between 2007 and 2008 China—the world’s largest steel producer and experiencing increases in con-struction, industrialization, and overall economic growth—is seen as an important current and future market for Kazakhstan’s chromium

Other Resources Kazakhstan, ranked eighth in the world in production

of manganese, is estimated to be home to the world’s

Workers stand behind vessels containing uranium, one of Kazakhstan’s main natural resources (Getty Images)

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second largest manganese reserves As of 2009,

pro-duction was at only 20 percent capacity, and all

man-ganese mining operations within Kazakhstan were

foreign owned

Kazakhstan is the eleventh largest producer among

countries of lead and has the fourth largest lead

re-serves Some estimates claim that global lead resources

will be exhausted by 2050, so Kazakhstan may become

a leading producer in coming decades Much of the

lead used now, however, is produced by recycled

mate-rials

Home to the world’s eleventh largest copper

re-serves, Kazakhstan is also the world’s eleventh largest

producer Kazakhmys, the largest copper producer in

Kazakhstan, exports 85 percent of its final product to

China Kazakhmys also produces silver, gold, and zinc

Kazakhstan is the world’s seventh largest producer

of zinc and is home to the world’s fifth largest

re-serves While zinc is an important input in the

galvani-zation of steel and the production of brass, its prices

have fallen steadily as global demand has dropped

precipitously The Kazakhstan metals company

Ka-zakhmys, in response to poor market conditions,

an-nounced in June, 2009, that it was suspending

opera-tions at its Balkhash zinc production facility

Kazakhstan is the eleventh largest producer of iron

ore in the world and is home to the world’s seventh

largest reserves Production has been declining in

re-cent years, however, and much of the country’s

depos-its are considered of low-grade quality

Kazakhstan’s other resources include important

animal and plant resources The Caspian Sea, for

ex-ample, is home to the endangered beluga sturgeon,

noted for its production of world-class caviar Apples

appear to have originated in Kazakhstan, where

for-ests of wild apples offer a vast genetic “library” for this

valuable plant Agricultural researchers have collected

seeds from Kazakhstan’s apple forests in an attempt to

conserve the biodiversity of apples in case the

mono-culture varieties that dominate world markets should

face catastrophic disease from pests, fungus, or

vi-ruses

Kristopher D White

Further Reading

Fergus, Michael, and Janar Jandosova Kazakhstan:

Coming of Age London: Stacey International, 2004.

Koven, Peter “Kazakhstan Unrest Dims Uranium Ore

Shares Forty Percent.” Financial Post, May 28, 2009.

Kramer, Andrew E “Capitalizing on Oil’s Rise,

Ka-zakhstan Expands Stake in Huge Offshore

Proj-ect.” The New York Times, January 15, 2008.

Lustgarten, Abrahm “Nuclear Power’s White-Hot

Metal.” Fortune 157, no 6 (March 31, 2008) Papp, John F “Chromium.” In 2006 Minerals Yearbook.

Denver, Colo.: U.S Geological Survey, 2008

Peck, Anne E Economic Development in Kazakhstan: The

Role of Large Enterprises and Foreign Investment New

York: Routledge, 2004

Pomfret, Richard “Kazakhstan’s Economy Since In-dependence: Does the Oil Boom Offer a Second

Chance for Sustainable Development?” Europe-Asia

Studies 57, no 6 (2005): 859-876.

Serafin, Tatiana “Emerging Market Gold Mine.”

Forbes 177, no 6 (March 27, 2006).

Timmons, Heather “Kazakhstan: Oil Majors Agree to

Develop Field.” The New York Times, February 26,

2006

See also: Chromium; Coal; Nuclear energy; Oil and natural gas reservoirs; Strategic resources; Uranium

Kyanite

Category: Mineral and other nonliving resources

Where Found Because metamorphosed high-alumina shales are common in the mountain belts of the world, kyanite group minerals are widely distributed However, con-centrations of the minerals in reasonably large crystal size are required for economic production Major kyanite ore reserves are found in the southern Appa-lachian Piedmont and in India Sillimanite has been mined in India, Australia, and South Africa Large de-posits of commercial-grade andalusite occur in France, South Africa, and North Carolina

Primary Uses Kyanite minerals are used in high-temperature metal-lurgical processes They are also used in high-strength porcelain manufacture

Technical Definition Kyanite is an aluminum silicate mineral, Al2SiO5, also written Al2O3CSiO2 Two other minerals, sillimanite and andalusite, have identical composition but crys-tallize in different forms determined by the

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ture and pressure at the time of crystallization The

three minerals are polymorphs (different forms) of

Al2SiO5 and constitute the kyanite, or sillimanite,

group of minerals

Description, Distribution, and Forms

Kyanite crystallizes as blade-shaped crystals with

vitre-ous luster and white to blue color Sillimanite is most

commonly finely fibrous and brown in color

Andalu-site occurs as elongate, cigar-shaped crystals in a

vari-ety of colors Kyanite-group minerals occur most

com-monly in metamorphosed high-alumina shales

Relatively high pressures and temperatures produce

kyanite, intermediate pressures and high

tempera-tures produce sillimanite, and low temperatempera-tures and

pressures produce andalusite

History

Kyanite has been mined in many parts of the world In

the past, it was treasured for its blue color Some

tradi-tions indicate kyanite has healing powers

Obtaining Kyanite

Kyanite minerals require varying amounts of

prepara-tion before use Massive aggregates of kyanite and

sillimanite that occur in India have been sawed or

carved to desired shapes, but kyanite group mineral

resources in Europe and North America normally

require separation of the minerals from associated

quartz, micas, and other minerals, resulting in a

gran-ular product The granules, which do not adhere to

one another, are mixed with various materials, usually

including fireclay and water, to produce a moldable

product that can be used as mortar between

refrac-tory bricks or molded into bricks or other useful

shapes

As a high-temperature furnace lined with “green”

(unfired) superduty refractory bricks is heated, the

kyanite group minerals in the green brick and mortar

convert to mullite Uniquely, the volume of mullite

and silica glass resulting from the conversion of

kyan-ite to mullkyan-ite is about 18 percent greater than the

orig-inal volume of kyanite The volume increase occurs at

about the same temperature that other materials are

shrinking in volume, and this phenomenon tends to

mechanically stabilize the furnace lining Therefore,

there is a significant advantage to including raw

kya-nite in the green products

Uses of Kyanite The kyanite group minerals are used as superduty refractories in high-temperature metallurgical pro-cesses, especially steel production, and in high-strength porcelain products, typically automobile spark plug insulators On heating to about 1,400° Cel-sius, the kyanite group minerals alter to mullite (3Al2O3C2SiO2) plus silica glass Mullite remains stable and strong to 1,810° Celsius The kyanite group min-erals are therefore very desirable as refractories in steel and glass furnace linings and as materials for kiln furniture (product supports) in high-temperature ce-ramic manufacture

Kyanite group minerals compete economically with synthetic mullite refractories Synthetic mullite is produced by heating or fusing an appropriate mix-ture of high alumina and siliceous materials Near Americus, Georgia, naturally occurring mixtures of

Kyanite is used in metallurgical processes and can range in color from white to blue (©John Carter/Dreamstime.com)

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bauxite and kaolin—and at Niagara, New York,

alu-mina and glass-grade silica sand—are used to produce

synthetic mullite

Robert E Carver

Web Site

U.S Geological Survey

Kyanite

http://minerals.usgs.gov/minerals/pubs/

commodity/kyanite/index.html#myb

See also: Ceramics; Clays; Metamorphic processes,

rocks, and mineral deposits; Minerals, structure and

physical properties of; Orthosilicate minerals

Kyoto Protocol

Category: Laws and conventions

Date: Produced in June, 1992; adopted for use on

December 11, 1997; entered into force February

16, 2005

The Kyoto Protocol is an environmental treaty created

to stabilize greenhouse gases (GHGs) in the

atmo-sphere It is a protocol to the United Nations

Frame-work Convention on Climate Change, which was

produced at the United Nations

Confer-ence on Environment and Development in

Brazil from June 3 to 14, 1992.

Background

In 1987, the Montreal Protocol was

es-tablished, creating a treaty to phase out

production of a major group of

indus-trial gases, including

chlorofluoro-carbons, that deplete the ozone layer

The Kyoto Protocol was established to

enhance energy efficiency in areas not

covered in the Montreal Protocol It

en-courages research and reform,

reduc-ing emissions of GHGs and methane, as

well as facilitation of measures to address

climate change The protocol includes

twenty-eight articles addressing climate

change in transport, energy, and industry

sectors and stresses the need for research,

publications, and periodic review of the

protocol

Provisions The Kyoto Protocol establishes legally binding com-mitments for the reduction of carbon dioxide (CO2), methane (CH4), nitrous oxide (N20), and sulfur hexa-fluoride (SF6) for developed countries for the

post-2000 period and control of hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs), produced by Annex I (industrialized) nations Cuts in these gases are measured against a baseline (from either 1990 or 1995)

As of 2008, 183 parties had ratified the Kyoto Pro-tocol with specific goals of quantified emissions lim-itation or reduction commitments of 5.2 percent

in comparison to 1990, collectively The developed countries committed to reducing emissions of the six key GHGs through cuts of as much as 8 percent For some countries, stabilization of emissions was the goal By 2005, progress had to be demonstrated in all countries, and targets were to be achieved between

2008 and 2012

Impact on Resource Use

In order for the impact of the protocol to be evalu-ated, countries were required to submit information

on their climate change programs and promote pub-lic awareness, education, and training Monitoring and compliance procedures were designed to deter-mine whether parties were fulfilling their obligations

Upon the adoption of the Kyoto Protocol, chairman Raul Estrada Oyuela shakes hands with a delegate, while other diplomats celebrate with applause (AP/Wide

World Photos)

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A national system for estimating the GHG emissions

was also required The protocol called for an expert

team to review the inventories and manage their GHG

portfolios, which all nations in Annex I and most of

the non-Annex I countries established

Ultimately, the protocol has forced countries to

ad-dress their overuse of fuels responsible for global

warming and gave them sufficient reason to reduce

local and regional air pollution Compliance was

ex-pected to reduce petroleum dependence and

ineffi-ciencies in energy production and use Further, the

economic burden of implementing the policies were

expected to be worth the investment, especially when

considering the socioenvironmental costs of not

abid-ing by the protocol

Germany, for example, reduced its GHG emissions

by 22.4 percent between 1990 and 2008, and in 2004, France shut down its last coal mine to decrease its CO2 emissions Overall, the Kyoto Protocol demonstrated that the world could produce the same amount of en-ergy with less coal, more gas, and the use of more renewable sources of energy

Gina M Robertiello

See also: Agenda 21; Climate Change and Sustain-able Energy Act; Edison Electric Institute; Green-house gases and global climate change; Intergovern-mental Panel on Climate Change; Montreal Protocol; United Nations climate change conferences; United Nations Framework Convention on Climate Change

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La Niña See El Niño and La Niña

Lakes

Category: Ecological resources

Lakes are inland bodies of water that fill depressions in

the Earth’s surface They are generally too deep to allow

vegetation to cover the entire surface and may be fresh

or saline.

Background

Lakes are standing bodies of water that occupy

hol-lows or depressions on the surface of the Earth Small,

shallow lakes are usually called ponds, but there is no

specific size and depth that are used to distinguish

ponds from lakes The scientific study of the physical,

chemical, climatological, biological, and ecological

aspects of lakes is known as limnology

Precipitation is the primary source of water for

lakes, in the form of either direct runoff by streams

that drain into a depression or groundwater that

slowly seeps into a lake by passing through subsurface

earth materials Although lakes are generally thought

of as freshwater bodies, many lakes in arid regions

be-come very salty because of the high evaporation rate,

which concentrates inflowing salts The Caspian Sea,

the Great Salt Lake, and the Dead Sea are classic

ex-amples of saline lakes

Although freshwater and saline lakes account for a

minute fraction of the world’s water—almost all of it is

in the oceans and in glaciers—they are an extremely

valuable resource In terms of ecosystems, lakes are

divided into a pelagial (open-water) zone and a

litto-ral (shore) zone where macrovegetation grows

Sedi-ments free of vegetation that occur below the pelagial

zone are in the profundal zone

The renewal time for freshwater lakes ranges from

one to one hundred years The length of time varies

directly with lake volume and average depth, and

indi-rectly with a lake’s rate of discharge The rate of

re-newal, or turnover time, for lakes is much less than

that of oceans and glacial ice, which is measured in thousands of years

Lake size varies enormously Lake sizes range from small depressions of a hectare or less to that of the Caspian Sea, the largest in the world, which covers 371,000 square kilometers This one body of saline water is larger than all of Germany The Great Lakes

of North America (Lakes Superior, Huron, Michigan, Erie, and Ontario) make up the largest continuous mass of fresh water on the planet, with a combined area of more than 245,000 square kilometers—larger than the total area of Great Britain The largest single freshwater lake in the world is Lake Superior, with a surface area of more than 82,000 square kilometers— nearly the size of Ireland Other major freshwater lakes include Lake Victoria in Africa, Lake Huron, and Lake Michigan, with approximate areas of 69,000, 60,000, and 58,000 square kilometers, respec-tively

Lake Baikal in Russia not only is the deepest lake in the world (1,620 meters) but also contains the largest amount of fresh water (23,600 cubic kilometers) This one lake alone contains approximately 20 percent of all of the fresh water in the world The combined vol-ume, 22,810 cubic kilometers, of all of the five Great Lakes is still less than Lake Baikal However, Lake Baikal and the Great Lakes account for more than 40 percent of the total amount of fresh water in the world The second and third largest freshwater lakes

in the world in terms of volume are Lake Tanganyika

in Africa and Lake Superior, with 18,900 and 12,100 cubic kilometers, respectively Lake Tanganyika is also the second deepest lake in the world (1,433 meters) Lake Titicaca in the Andes Mountains of Peru and Bo-livia is the highest lake in the world at 3,800 meters el-evation, while the Dead Sea in Israel and Jordan is the lowest, at an elevation of 422 meters below sea level

Origins of Lakes Lakes are unevenly distributed on the Earth’s surface Nearly half of the world’s lakes are in Canada, and Minnesota is proud of its reputed count of ten thou-sand lakes Both Canada and Minnesota were deeply affected by continental glaciation during the various

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stages of the Pleistocene epoch, or

Ice Age, which lasted for

approxi-mately two million years In fact, most

of the world’s lakes were formed as

a consequence of the movement of

continental ice sheets during the

Pleistocene For example, the Great

Lakes were formed by advancing ice

sheets that carved out large basins

in the bedrock In many other

in-stances, existing valleys were eroded

and deepened by glacial advance,

resulting in the formation of large

lakes such as Great Bear Lake and

Great Slave Lake in central Canada

(31,153 and 27,200 square

kilome-ters, respectively) In some instances,

long, narrow valleys were oriented

parallel to the movement of the ice

sheet When the ends of these valleys

became blocked by glacial debris,

the basins filled up with water to form long, narrow

lakes The Finger Lakes of western New York State

provide an excellent example of this process

Numer-ous small lakes and ponds were formed in kettles,

which are small depressions found in glacial deposits

called moraines Blocks of stagnant ice that became

trapped in the morainal deposits melted and formed

kettle lakes Minnesota and many other areas in the

upper Midwest and central Canada have numerous

kettle lakes with this type of origin

Tectonic activity in the crust of the Earth formed

lake basins in a number of ways For example, faulting

results in rift valleys that can fill with water The

downfaulted block is referred to as a graben and

ac-counts for the deepest lakes in the world, Lakes Baikal

and Tanganyika These lakes are also unusual in that

they contain a large number of relict endemic species

of plants and animals More than 80 percent of the

plant and animal species in Lake Baikal are endemic

only to this lake Examples of graben lakes in the

United States include Lake Tahoe, in the Sierra

Mountains of California and Nevada, and Pyramid

Lake, north of Reno in Nevada The Truckee River

flows from Lake Tahoe into Pyramid Lake

Several large, isolated lake basins have resulted from

tectonic movements that caused a moderate uplift of

the marine seabed The Caspian Sea and the Aral Sea

in central Asia were separated by uplifted mountain

ranges in the Miocene epoch (from 5 to 24 million

years ago) Lake Okeechobee in central Florida, which

is the second largest freshwater lake in the cotermi-nous United States (Lake Michigan is the largest), with an area of 1,890 square kilometers, was a shallow depression in the seafloor when it was uplifted during the Pliocene epoch some 2 to 5 million years ago as part of the formation of the Floridian peninsula The third major natural cause of lakes is volcanic activity Lava flows can block stream valleys and form lake basins, and collapsing volcanic craters form large basins called calderas Crater Lake in Oregon, with an area of 64 square kilometers and a depth of 608 me-ters (making it the ninth deepest in the world), is a well-known example of a caldera lake The fourth type

of natural origin occurs in humid regions underlain

by limestone This type of rock is susceptible to disso-lution by percolating water In time, the limestone goes into solution, and the result is a conical and cir-cular sinkhole These sinkhole lakes are very common

in limestone areas of the Balkans and the midwestern United States and in central Florida Oxbow lakes de-velop in meandering stream channels of gently slop-ing alluvial floodplains that have been abandoned by lateral shifts of the river These are common in the floodplain of the lower Mississippi River

Lakes, whatever the nature of their origin, are ephemeral features on the Earth’s surface In contrast

to many other landforms on the Earth, such as moun-tains and valleys, lakes are transient Drier climatic

Aerial view of Lake Huron, one of North America’s five Great Lakes.

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conditions, erosion of an outlet, natural and

human-induced sedimentation, water diversion, and nutrient

inflow inexorably result in a short life span of

hun-dreds to thousands of years On a geological

time-scale, this longevity is extremely short

Lake Stratification

Solar heating of a lake results in thermal stratification,

which is a major factor in lake structure This process is

the most important physical event in the annual cycle

of a lake Thermal stratification is common in many

midlatitude lakes that are deeper than approximately

10 meters During the high Sun or summer months,

an epilimnion—a warm, lighter, circulating, and

rela-tively turbulent layer—develops in the surface waters;

it has a range of thickness of about 2 to 20 meters A

lower level of denser, cooler, and relatively quiet water

develops below the epilimnion The vertical extent of

this hypolimnion level can be large or small,

depend-ing on the depth of the lake The thermocline, or

metalimnion, forms a zone of transition between the

two layers where the temperature changes abruptly

It is generally several meters in thickness The

strat-ification is not caused by the temperature change

but rather by the difference in the densities of the

water in the epilimnion (lighter) and the

hypolim-nion (heavier) As the fall season approaches, heat

loss from the surface exceeds heat inputs, and the

epilimnion cools, becomes denser, and mixes with the

deeper layers Eventually, all of the water in the lake is

included in the circulation as the fall turnover begins

Most lakes experience a seasonal cycle of stratification

and mixing that is a key component of their ecology

Reservoirs

Reservoirs are artificial lakes; they range from small

farm or fish ponds of less than a hectare in size to

mas-sive impoundments The three largest reservoirs in

terms of capacity are Lake Kariba on the Zambezi

River, which forms the boundary between Zimbabwe

and Zambia in Africa; Bratsk on the Angara River in

Siberia; and Lake Nasser on the Nile in Egypt The

largest reservoirs in the United States are Lake Mead

and Lake Powell on the Colorado River Reservoirs are

built for hydropower, flood control, navigation, water

supply, low flow maintenance for water quality

pur-poses, recreation, or any combination thereof

Reser-voir management is a specialized field, since water

re-leases and storage requirements must fit in with the

operating schedule for each system and watershed

Although dams and reservoirs have brought many benefits to society, they are associated with several en-vironmental problems For example, the dams on the Columbia River in the Pacific Northwest inhibit the ability of salmon to return upstream where they spawn Fish ladders have provided only a partial solu-tion to this problem Large impoundments such as Lake Mead (behind Hoover Dam on the Colorado River) can store so much water that the additional weight on the Earth’s crust has been linked to small to moderate earthquakes in parts of Nevada hundreds

of kilometers away Reservoirs, by design, regulate the flow of water downstream In the process of doing so, they deny the river its normal seasonal flush of water

in the spring, which is necessary for a healthy aquatic ecosystem As a means of addressing this flushing problem on the Grand Canyon portion of the Colo-rado River, a large amount of water was released from Lake Powell, which is upstream from the Grand Can-yon, in a short period of time so as to replicate the spring flood Considerable hydropower revenues were lost in this experiment, but there were many benefits

to the ecology of the river

Eutrophication The aging of a lake by biological enrichment is known

as eutrophication The water in young lakes is cold and clear, with minimal amounts of plant and animal life The lake is then in the oligotrophic state As time goes on, streams that flow into the lake bring in nutri-ents such as nitrates and phosphates, which encour-age aquatic plant growth As the fertility in the lake increases, the plant and animal life increases, and or-ganic remains start accumulating on the bottom The lake is in the process of becoming eutrophic Silt and organic debris continue to accumulate over time, slowly making the lake shallower Marsh plants that thrive in shallow water start expanding and gradually fill in the original lake basin Eventually the lake be-comes a bog and then dry land

This natural aging of a lake can take thousands of years, depending upon the size of the lake, the local cli-mate, and other factors However, human activities can substantially accelerate the eutrophication process Among the problems caused by humans are the pollu-tion of lakes by nutrients from agricultural runoff and poorly treated wastewater from municipalities and in-dustries The nutrients encourage algal growth, which clogs the lake and removes dissolved oxygen from the water The oxygen is needed for other forms of aquatic

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life The lake enters a hypereutrophic state as declining

levels of dissolved oxygen result in incomplete

oxida-tion of plant remains, a situaoxida-tion that eventually causes

the death of the lake as a functioning aquatic

ecosys-tem In a real sense, the lake chokes itself to death

Climatic Effects

Lakes moderate local climates Since the specific heat

of water is five times that of dry land, lakes ameliorate

cold-air-mass intrusions in midlatitude regions The

resultant extension of the frost-free period can be

ex-tremely beneficial to agriculture The successful

vine-yards on the shores of the Finger Lakes in New York

and the fruit-tree belts in upper New York just south of

Lake Ontario are a well-known example of this

bene-fit Even in Florida, the presence of Lake Okeechobee

helps the agricultural areas on the southern and

southeastern shores; cold air from the northwest is

warmed as it passes over the lake

The Great Lakes are associated with a “lake effect”

that results in additional snow falling in those areas

where cold Canadian air masses pass over the lakes

from the northwest in the winter, pick up moisture

from the relatively warmer water, and then precipitate

the snow on the southern and eastern shores of the

lakes The amounts of snow deposited during these

routine occurrences can be substantial

Robert M Hordon

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