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Disappearing Lakes, Shrinking Seas

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  • mtneuman@juno.com
    Eco-Economy Update 2005-3 For Immediate Release April 7, 2005 DISAPPEARING LAKES, SHRINKING SEAS http://www.earth-policy.org/Updates/2005/Update47.htm Janet
    Message 1 of 1 , Apr 8, 2005
      Eco-Economy Update 2005-3
      For Immediate Release
      April 7, 2005

      DISAPPEARING LAKES, SHRINKING SEAS
      http://www.earth-policy.org/Updates/2005/Update47.htm

      Janet Larsen


      West Africa's Lake Chad has shrunk to a mere 5 percent of its former
      size.
      Central Asia's Aral Sea is shrinking, gradually turning into desert. In
      Israel, the receding shores of Lake Tiberias-also known as the Sea of
      Galilee-sometimes allow mere mortals to walk where the water once was.
      Thousands of lakes in China have disappeared entirely. The diversion of
      river water in India and Pakistan that allowed for a doubling of
      irrigated
      area over the last four decades has depleted many lakes. All told, more
      than half of the world's 5 million lakes are endangered.

      For more than 4,000 years, farmers have diverted river water for crops in
      dry areas and dry seasons, reducing the flow into nearby lakes and seas.
      Over the last half-century world water use has tripled, expanding faster
      than population. Today irrigation accounts for two thirds of global water
      use. With the advent of diesel and electrically driven pumps, groundwater
      extraction in some areas has exceeded recharge from precipitation, also
      causing water tables and lake levels to fall.

      Nestled among deserts, the 5-million-year-old Aral Sea is one of the
      world's most ancient lakes. As recently as the early 1960s, it covered
      some 66,000 square kilometers (25,483 square miles) and held 1,000 cubic
      kilometers (264 trillion gallons) of water. Two rivers, the Amu Darya and
      Syr Darya, fed the lake with some 65 cubic kilometers of water each year.
      Today, however, irrigation of vast fields of cotton has drained the
      rivers, reducing the annual inflow to only 1.5 cubic kilometers. As a
      result the Aral has lost four fifths of its volume and split into two
      sections.

      The shoreline of the Aral Sea has receded by up to 250 kilometers,
      leaving
      behind a salty desert. The United Nations estimates that every day
      200,000
      tons of salt and sand containing residual agricultural chemicals and
      heavy
      metals from the uncovered seabed are carried by the wind and dumped on
      farmland within a 300-kilometer radius, destroying pastures and arable
      land. The pollution of air, land, and water has left a legacy of diseases
      such as cancer, cholera, and typhus. The once-prolific fishery has been
      destroyed.

      Growing water demands are causing other lakes around the globe to vanish.
      (See http://www.earth-policy.org/Updates/2005/Update47_data.htm for
      additional
      examples and data.) Irrigation withdrawals from the waters that feed
      Africa's Lake Chad quadrupled between 1983 and 1994. Water consumption,
      combined with low rainfall levels since the 1960s, has shrunk the lake by
      95 percent, from 25,000 square kilometers to 1,350 square kilometers,
      over
      the past 35 years.

      Overpumping groundwater in China's Hebei province has lowered the water
      table, resulting in the loss of 969 of the province's 1,052 lakes. Madoi
      County in northwest China's Qinhai province, the first through which the
      main stream of the Yellow River flows, once had 4,077 lakes. Over the
      past
      20 years, more than half have disappeared.

      In 1998, China's largest river, the Yangtze, experienced devastating
      flooding, taking the lives of 3,600 people and wreaking more than $30
      billion in damages. The floods were largely attributed to the cutting of
      forests and the loss of more than 13,000 square kilometers of lake area
      along the Yangtze's middle and lower reaches. Prior to the flooding, some
      800 lakes had disappeared entirely, depriving the basin of needed water
      storage capacity and flood protection. Following the floods the Chinese
      government pledged action to restore both forests and lakes.

      Tonle Sap in Cambodia, Southeast Asia's largest freshwater lake, supports
      one of the world's largest inland fisheries. Like many lakes it has long
      provided flood protection, fluctuating in volume according to rainfall
      and
      climate. Now, however, eroding deforested and farmed land is silting up
      the lake and reducing its storage capacity, ultimately increasing the
      region's vulnerability to the opposing extremes of flooding and water
      scarcity. The Hamoun Lakes and nearby wetlands in Iran and Afghanistan's
      Sistan Basin are similarly losing their ability to mitigate floods as
      they
      are drying from the damming of the Helmand River and years of drought.

      Mono Lake, North America's oldest, dating back some 760,000 years, is an
      important feeding stop for migrating birds, especially as southern
      California has lost over 90 percent of its wetlands. Since the first
      diversions of its tributaries to quench the thirst of growing Los Angeles
      in 1941, the lake has contracted dramatically, with water level dropping
      by 11 meters (34 feet) and volume down 40 percent. As a result, its
      salinity has jumped to three times that of the ocean-far too salty to
      sustain most fish. The lake likely would have died completely had locals
      not intervened and defeated Los Angeles in a legal battle over keeping
      water for the lake.

      Mexico's largest lake, Chapala, is the primary source of water for
      Guadalajara's growing population of 5 million. This lake's long-term
      decline began in the 1970s, corresponding with increased agricultural
      development in the R�o Lerma watershed. Since then, the lake has lost
      more
      than 80 percent of its water. Between 1986 and 2001, Chapala shrank in
      size from 1,048 to 812 square kilometers. Climbing municipal and
      industrial water demands now exceed the sustainable supply by 40 percent.
      The lake's contraction has come at the expense of several fish species
      and
      potentially presages a change in the mild climate that the water
      supported.

      Lakes are not only being drained dry; they also are dying from
      contamination. Farm wastes, sewage, and nitrogen fallout from fossil fuel
      burning fertilize lakes, causing excess algal and plant growth that
      depletes water oxygen levels and kills aquatic animal life. Such
      eutrophication plagues more than half the lakes in Europe and Asia, 41
      percent of those in South America, and 28 percent in North America.

      Acid precipitation, largely from fossil fuel burning emissions, is
      killing
      thousand of lakes. An estimated 120,000 square kilometers of lakes in
      Norway are acidified to the point where fish stocks have crashed. Sweden
      has some 4,000 acidified lakes. In Canada, some 14,000 lakes are severely
      acidified. The U.S. Environmental Protection Agency estimates that some
      70
      percent of sensitive lakes in New York's Adirondack Mountains are at risk
      of periodic acidification, and that without further reductions in sulfur
      dioxide emissions the rate of acidification will increase by half or
      more.

      A survey of remote mountain lakes throughout Europe found that even lakes
      far from human development were acidified by sulfur and nitrogen
      deposition and that virtually all were contaminated by heavy metals (such
      as mercury, lead, and cadmium) and fly ash particles. The sediments and
      fish in these lakes also contained a wide range of persistent organic
      pollutants.

      Rising global temperatures are predicted to increase average lake
      temperatures by 2-3 degrees Celsius (3.6-5.4 degrees Fahrenheit) over the
      next 50 years. Unfortunately, as water warms, its natural purification
      processes can slow down. Climate-related changes in water chemistry and
      stratification can lead to fish losses, as is already being seen in East
      Africa's Lake Tanganyika.

      More than 2 billion people live in countries with chronic water stress.
      Many of the world's people, especially in developing countries, depend on
      fish for protein. Lakes are not only reservoirs of fresh water and a
      source of food, but also important habitats for aquatic organisms and
      waterfowl. Lakes reduce flood damage, moderate climate, and recharge
      groundwater supplies. They also offer transportation and recreational
      opportunities and income from tourism. With all the benefits that we
      derive from healthy lakes, we cannot afford to let them disappear.

      # # #

      Additional data and information sources at www.earth-policy.org or
      contact
      jlarsen@...

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