West Africa's Lake Chad has shrunk to a mere 5% 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 water once was.
|Lakes offer transportation and recreational opportunities — and income — from tourism. With all the benefits from healthy lakes, we cannot afford to let them disappear.|
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 five 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 has exceeded recharge from precipitation in some areas, causing water tables and lake levels to fall.
Losing the Aral Sea
Nestled among deserts, the 5-million-year-old Aral Sea is one of the world's most ancient lakes.
|Water consumption, combined with low rainfall levels since the 1960s, has shrunk Lake Chad by 95%, from 25,000 square km to 1,350 square km over the past 35 years.|
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, the irrigation of vast fields of cotton has drained the rivers and reduced 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.
A salty desert
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 Aral Sea’s uncovered seabed are carried by the wind — and then dumped on farmland within a 300-kilometer radius, destroying pastures and arable land.
Destroyed fisheries and water quality
The resulting pollution of air, land and water has left a legacy of diseases such as cancer, cholera and typhus. The Aral's once-prolific fishery has been destroyed.
|Over the last half century, world water use has tripled, expanding faster than population. Today, irrigation accounts for two-thirds of global water use.|
Growing water demands are causing other lakes around the globe to vanish. Click here for additional examples.
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%, from 25,000 square kilometers to 1,350 square kilometers, over the past 35 years.
Over used and over pumped
In China's Hebei province, over-pumping groundwater 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.
|In Israel, the receding shorelines of Lake Tiberias — also known as the Sea of Galilee — sometimes allows mere mortals to walk where water once was.|
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.
Benefits of healthy 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 rainfall and climate. Now, however, eroding deforested and farmed land is silting up the lake and reducing its storage capacity. Ultimately, this increases the region's vulnerability to the opposing extremes of flooding and water scarcity.
Saving Mono Lake
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.
|Today, irrigation of vast fields of cotton has drained the rivers — and as a result, the Aral Sea has lost four- fifths of its volume and split into two sections.|
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% 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%. 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 Lake Chapala
Mexico's largest lake, Chapala, is the primary source of water for Guadalajara's growing population of five million. This lake's long-term decline began in the 1970s, corresponding with increased agricultural development in the Río Lerma watershed.
Since then, the lake has lost more than 80% 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%.
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.
|Mono Lake — North America’s oldest lake — likely would have died completely had locals not intervened.|
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 — cause excess algal and plant growth that in turn, depletes water oxygen levels and kills aquatic animal life.
This process, called eutrophication, plagues more than half the lakes in Europe and Asia, 41% of those in South America — and 28% 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% of sensitive lakes in New York's Adirondack Mountains are at risk of periodic acidification. It also believes that without further reductions in sulfur dioxide emissions the rate of acidification will increase by half or more.
Human development and water stress
A survey of remote mountain lakes throughout Europe found that even lakes far from human development were acidified by sulfur and nitrogen deposition. Virtually all were contaminated by heavy metals (such as mercury, lead and cadmium) and fly ash particles.
|In China, prior to the flooding of the Yangtze River, some 800 lakes had disappeared entirely — depriving the basin of needed water storage capacity and flood protection.|
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 two billion people live in countries with chronic water stress. Many of the world's people, especially in developing countries, depend on fish for protein.
Losing our lakes
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.