Lakes created by hydroelectric dams impound 13 percent of the organic carbon carried by rivers into oceans, a peer-reviewed study published in Nature Communications reports. By removing carbon from the carbon cycle, hydroelectric dams may be doing more to mitigate global warming than simply producing emissions-free power.
An international team of scientists studied the transport of organic carbon via river systems into the oceans. Looking at data for the year 2000, the team discovered “dams lowered the OC [organic carbon] export to the global coastal zone via rivers by 13%.” Seven percent was due to lakes sequestering carbon in sediments, and six percent was due to mineralization of carbon.
Hoover Dam. Photo courtesy of Pixabay.
“At the global scale, dams represent a net sink for riverine OC,” the study concludes.
With more dams currently being built – primarily outside the United States – organic carbon sequestration by dams may reach 19 percent by 2030, the scientists report.
“All other factors equal, by eliminating OC more efficiently than nutrients, river damming should enhance carbon fixation over mineralization in the receiving waters,” the study notes.
Hydro power is the most cost-effective source of emissions-free power. The new evidence that hydroelectric dams impound carbon in addition to producing zero-emissions power makes the environmental case for hydro power even more compelling.