COLUMBUS, Ohio For the first time, scientists have been able to measure the amount of water that rises and falls annually in the Amazon River floodplain.
The result -- 285 billion metric tons, or 285 cubic kilometers of water by volume -- sounds like a lot. That amount is over half the volume of Lake Erie, which is the world's 15th largest lake.
But it accounts for only 5 percent of the water flowing through the Amazon River every year, and it is a much smaller amount than researchers were expecting to find in the largest drainage basin in the world.
Doug Alsdorf, associate professor of earth sciences at Ohio State University, and his colleagues report their study online in the journal Remote Sensing of Environment, in a paper to appear in a future print edition.
Until now, researchers could only estimate the amount of water in the Amazon floodplain using a few sporadic field studies and crude assumptions about water flow. In fact, water volumes on any floodplain are poorly known, if at all. Yet this information is critical to predicting the floods and droughts that could accompany global climate change, explained Alsdorf.
Much of Earth's available fresh water resides in remote rivers, lakes and wetlands, and also underground.
"Nobody knows exactly how much water there is on the planet," he said. "We need to understand how our water supply will change as the climate changes, and the first step is getting a handle on how much water we actually have."
Alsdorf and his team have made it their mission to find ways to measure water from space.
"Satellite observations are the only reliable option for places like the Amazon and especially the Congo Basin, where in-person measurements are near-impossible. Just getting there is a serious challenge," he said.
For this study, the researchers were interested only in the amount of water that flowed into and out of the floodplain -- that
|Contact: Doug Alsdorf|
Ohio State University