A new global warming offender: Dam drawdowns (+video) - The Petri Dish

This article was updated with a video at 6:29 a.m. EDT.

According to a new Washington State University report, WSU researchers have discovered a new global warming culprit: Dam drawdowns. In fact, researchers contend that dam drawdowns cause significant increases in greenhouse gases.

The study found that methane emissions skyrocketed 20-fold when the water level was drawn down at Lacamas Lake in Clark County. Bubbles rising from Lacamas Lake were found to have a 36-fold rise in methane during a dam drawdown.

Researchers say that methane is a powerful greenhouse gas, as it is 25 times more effective than carbon dioxide at keeping heat in the atmosphere. Dam drawdowns contribute to global warming because the approximately 80,000 dams in the United States contain biological activity that can generate copious amounts of greenhouse gases.

“Reservoirs have typically been looked at as a green energy source,” says Bridget Deemer, a doctoral student at Washington State University-Vancouver. “But their role in greenhouse gas emissions has been overlooked.”

Ms. Deemer and her research partner are trying to contribute to efforts to realize the role of lakes, reservoirs and stream in the release of greenhouse gases. Their research is especially important, as a 2011 study concluded that that ability of terrestrial ecosystems to soak up greenhouse gas emissions could be one-fourth less than estimated once emissions from reservoirs are taken into consideration.

The WSU study is the first study to quantify the relationship between dam drawdowns and greenhouse gas releases. John Harrison, an assistant professor of Earth and Environmental Sciences, says that their research could help dam engineers mitigate greenhouse gas emissions. In fact, Mr. Harrison says that the summer months may be the worst time to execute a dam drawdown, as warmer temperatures may facilitate an increase in greenhouse gas emissions during the drawdown.

“We have the ability to manage the timing, magnitude and speed of reservoir drawdowns, which all could play a role in how much methane gets released to the atmosphere,” Mr. Harrison says.

At this point, Ms. Deemer says researchers “simply don’t know” whether decommissioning a dam would have a net positive effect on the release of greenhouse gases.