Usually, western Namibia is a dusty place where the stream beds are sand and the "lakes" are nothing more than flats of dried mud. But in 2011, rivers with names like Swakop and Omaruru and Kuiseb flowed all the way to the sea--something that happens maybe "once a decade," says Paul Bierman of the University of Vermont. Bierman and Kyle Nichols of Skidmore College, both geologists, have been working for more than a decade in Namibia, collecting samples of rock and river sediment, and bringing them back for analysis. See more in this news release photo gallery.
Credit: Paul Bierman, UVM
Researchers eavesdropping on complex signals from a remote Wisconsin lake have detected what they say is an unmistakable warning--a death knell--of the impending collapse of the lake's aquatic ecosystem. Find out more in this news release.
Credit: Steve Carpenter
Rivers and streams supply the lifeblood to ecosystems across the globe, providing water for drinking and irrigation for humans as well as a wide array of life forms from single-celled organisms up to the fish humans eat. But humans and nature itself are making it tough on rivers to continue in their central role to support fish species. Read more in this news release.
Credit: Thomas Ross Reeve, Bureau of Reclamation
Witold Krajewski and his colleagues at the University of Iowa gained a rare opportunity to study the geophysical aspects of flooding in real time and to analyze the after-effects of flooding on residents. The university was caught in the path of rising flood waters in June 2008. The deluge overwhelmed streams and breeched levees in populated areas such as Cedar Rapids and Iowa City, where the Cedar and Iowa Rivers crested at unprecedented heights. Read more in this Discovery.
Credit: IIHR--Hydroscience and Engineering
The Division of Behavioral and Cognitive Sciences (BCS) of the Directorate for Social, Behavioral and Economic Sciences supports research to develop and advance scientific knowledge on human cognition, language, social behavior and culture, as well as research on the interactions between human societies and the physical environment.
A borrowed boat, a small mountain lake and the inaugural run of a state-of-the-art multi-beam sonar system made history in July 2010 with the successful high-definition mapping of the bottom of Fallen Leaf Lake, a tributary lake just upstream from Lake Tahoe.
The growing number of dams and other impoundments is increasing the number of invasive species and the speed at which they spread, putting natural lakes at risk, according to a study lead by the University of Colorado at Boulder. The research team combined data on water chemistry, the distribution of five "nuisance invaders" and boating activity from the Great Lakes region.
November 7, 2011
Dams--What Goes Up Must Come Down, and Then What?
Scientist monitors how ecosystem regroups after dam removal
Time can take its toll on a dam. As dams age, they are more costly to repair and the risk of a catastrophic dam break increases--putting property and lives at risk. But, removing them can mean big changes to the community, and the environment.
"A lot of communities now are trying to wrestle with the decision of whether or not to support dam removal. And part of that uncertainty is our lack of scientific knowledge of what's going to happen when you take a dam out," says Dartmouth College geographer Frank Magilligan.
With support from the National Science Foundation (NSF), Magilligan studies river systems to learn how dam removal might affect them. His "lab" has been the relatively small Homestead Dam along the Ashuelot River in Swanzey, N. H., 60 miles south of his campus office. The Homestead Dam was built more than 200 years ago along the Ashuelot. It's long outlived its purpose, once serving as a power source for a local mill that is long gone.
When Magilligan heard the dam was going to be taken down in July 2010, he rushed with a team of researchers to the dam site. "We were really fortunate because we were able to get in several months before the dam came out to get all the necessary pre-removal data," says Magilligan.
One set of data is LIDAR imagery of the Ashuelot. LIDAR uses a laser-based ranging tool mounted on the bottom of a small plane. It can peer beneath vegetation showing the Ashuelot's former riverbed from centuries ago.
"LIDAR is a very sophisticated laser system. What [we're] able to do is pick up very detailed, centimeter-scale topographic elevation," says Magilligan. LIDAR can get those precise measurements in just a few hours, giving a more accurate snapshot of the river's flow at any given point in time. It's the kind of work that might take months to complete by ground surveillance.
A year after the dam's removal, the team has now returned to the Ashuelot to get new LIDAR measurements to pinpoint where the river is currently flowing.
"We'll be able to document a topographic snapshot before the dam was removed and a topographic snapshot a year after the dam was removed," says Magilligan. LIDAR doesn't penetrate water, so grad student John Gartner resorts to a little help from a GPS device.
"As part of the GPS analysis we're able to get centimeter-scale topographical information," explains Magilligan, who also studies the riverbed sediment to track how the path of the river is changing. Magilligan finds there have been notable differences since the dam's removal. "What we have seen from some of our field analysis is that there's been a couple of feet of bank erosion in some places. In other places, we see a couple of feet of bank deposition as well," he notes.
For Magilligan, it's all about "shoring up" what we know about how rivers flow, in order to make smart choices when it is time for a dam to come down.
Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.