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10 Things You Should Know About Dams

Energy

1. 50,000 Large Dams Are Clogging the World's Rivers:

About 50,000 dams with a height of 15 meters or more and millions of smaller dams have been built on the world's rivers. Some of them date back centuries, but most were built after World War II. About 5,000 dams have a height of 60 meters or more—another 350 such giants are currently under construction.

The Grand Coulee dam on the Columbia River in Washington State was constructed between 1933-1942. Photo credit: Wikimedia Commons

2. Dams Are Changing the Face of the Earth:

Dams have fragmented two-thirds of the world's large rivers and flooded a land area the size of Spain. Their reservoirs contain three times as much water as all the world's rivers, and constantly lose close to four Niagara Falls to evaporation. Dams trap 40 cubic kilometers of sediments every year, and starve deltas of the silt that protects them against the intruding sea.

3. Dams Provide Important Services:

Dams generate 16 percent of the world's electricity and irrigate food crops for 12-15 percent of the world's population. To a lesser extent, dams have also been built for water supply, flood protection, navigation and tourism purposes. Most dams have been built for irrigation, but 80 percent of the water they store is used for hydropower.

4. Dams Kill Fish:

Dams block the migration of fish, deplete rivers of oxygen and interfere with the biological triggers that guide fish. They also reduce the ability of rivers to clean themselves. Due to dam building and other factors, the population of freshwater species declined by 37 percent between 1970-2008—more than the populations of any other ecosystems. Tropical freshwater populations declined by a stunning 70 percent.

5. Dams Are Changing the Climate:

Dams are not climate-neutral. Particularly in the tropics, organic matter rotting in their reservoirs emits methane, an aggressive greenhouse gas. Scientists have estimated that reservoirs account for four percent of all human-made climate change, equivalent to the climate impact of aviation. The floods and droughts caused by climate change in turn make dams less safe and less economic.

6. Dams Displace People:

Dams have displaced an estimated 80 million people, with 23 million alone in China. Displacement robs people who are already poor and marginalized of their resources, skills and cultural identity, and impoverishes them further. Dams have also negatively impacted about 500 million people living downstream. The benefits of dams often bypass the people who sacrifice their livelihoods for them.

7. Dams Can Put Human Rights at Risk:

Most dams that displace large populations are being built by authoritarian governments. In Burma, China, Colombia, Ethiopia, Guatemala, Sudan and other countries, dam builders have often responded to opposition with serious human rights violations. In the worst dam-related massacre, more than 440 indigenous people were killed to make way for Guatemala's Chixoy Dam in 1982.

The Chixoy Dam in Guatamala was completed in 1982. Photo credit: Wikimedia Commons

8. Dams Are Expensive:

Large dams belong to the most expensive investments many governments have ever made. An estimated 2,000 billion dollars has been spent on dams since 1950. Due to planning errors, technical problems and corruption, dams experience average delays of 44 percent and cost overruns of 96 percent. Such massive overruns make them uneconomic.

9. Dams Don't Last Forever:

Sooner or later reservoirs silt up, and the cost of maintaining dams becomes bigger than their benefits. In the U.S., more than 1,000 dams have been removed at great cost. When dams are not properly built or maintained, they can break. In the world's biggest dam disaster, the failure of China's Banqiao Dam killed an estimated 171,000 people in 1975.

10. Better Solutions Are Usually Available:

In 2012, governments and businesses installed 75 gigawatt of wind and solar power, compared with 30 gigawatt of hydropower. Such alternatives fare even better when social and environmental impacts and transmission costs are included. The International Energy Agency has proposed that 60 percent of the funds needed to achieve energy access for all should go to local renewable energy projects.

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On Thursday, the U.S. Drought Monitor said nearly 60 percent of the state was abnormally dry, up from 46 percent just last week, according to The Mercury News in San Jose.

The dry winter has included areas that have seen devastating fires recently, including Sonoma, Napa, Lake and Mendocino counties. If the dry conditions continue, those areas will once again have dangerously high fire conditions, according to The Mercury News.

"Given what we've seen so far this year and the forecast for the next few weeks, I do think it's pretty likely we'll end up in some degree of drought by this summer," said Swain, as The Mercury News reported.

Another alarming sign of an impending drought is the decreased snowpack in the Sierra Nevada Mountain range. The National Weather Service posted to Twitter a side-by-side comparison of snowpack from February 2019 and from this year, illustrating the puny snowpack this year. The snow accumulated in the Sierra Nevadas provides water to roughly 30 percent of the state, according to NBC Los Angeles.

Right now, the snowpack is at 53 percent of its normal volume after two warm and dry months to start the year. It is a remarkable decline, considering that the snowpack started 2020 at 90 percent of its historical average, as The Guardian reported.

"Those numbers are going to continue to go down," said Swain. "I would guess that the 1 March number is going to be less than 50 percent."

The National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center forecast that the drier-than-average conditions may last through April.

NOAA said Northern California will continue deeper into drought through the end of April, citing that the "persistent high pressure over the North Pacific Ocean is expected to continue, diverting storm systems to the north and south and away from California and parts of the Southwest," as The Weather Channel reported.

As the climate crisis escalates and the world continues to heat up, California should expect to see water drawn out of its ecosystem, making the state warmer and drier. Increased heat will lead to further loss of snow, both as less falls and as more of it melts quickly, according to The Guardian.

"We aren't going to necessarily see less rain, it's just that that rain goes less far. That's a future where the flood risk extends, with bigger wetter storms in a warming world," said Swain, as The Guardian reported.

The Guardian noted that while California's reservoirs are currently near capacity, the more immediate impact of the warm, dry winter will be how it raises the fire danger as trees and grasslands dry out.

"The plants and the forests don't benefit from the water storage reservoirs," said Swain, as The Mercury News reported. "If conditions remain very dry heading into summer, the landscape and vegetation is definitely going to feel it this year. From a wildfire perspective, the dry years do tend to be the bad fire years, especially in Northern California."