The Colorado River isn’t what it used to be. Because it is so important to so many communities, it has been tinkered with for years. The Hoover Dam and others like it along the Colorado River have resulted in river water rarely reaching the ocean. The Colorado River now has a dry delta, and where once there were healthy wetlands, they’ve been reduced to about 5% of their original size. Invasive plant species have replaced many native species, which has reduced biodiversity and negatively impacts the ecosystem.
That’s why the federal government released 130 million cubic meters of water (about 52,000 Olympic swimming pools) into the river basin in order to kick start the river again. That’s still only about 1% of the total water that used to flow down the Colorado. The goal is to get wetlands and river ecosystems back in action and to provide more water for agriculture and other uses. This kind of flooding is a useful tactic that has been used elsewhere.
But researchers attached to the project learned something new about this process: wetting dry riverbeds in this way releases a great deal of carbon and other greenhouse gases that would otherwise have been stored in the ground. Some of it thousands of years old. These gases are released into the water and, presumably, into the atmosphere as well. Water is an excellent system for trapping such gases, but it can only hold so much. Too much carbon in water makes it acidic, which is bad for wildlife.
Overall, though, the researchers are confident that the benefits of rewetting the riverbed outweigh this potential downside. One such benefit is the fact that rewetting the riverbed can lead to a flourishing of indigenous plants, which are better at trapping carbon than invasive species. That new growth in and of itself may offset the additional release of greenhouse gases.