— USGS (@USGS) May 4, 2015
A huge shout out to all of you government types that have a part if providing clean water to the masses!
— USGS (@USGS) May 1, 2015
Here’s the release from the USGS and USFS:
More than 1,000 dams have been removed across the United States because of safety concerns, sediment buildup, inefficiency or having otherwise outlived usefulness. A paper published today in Science finds that rivers are resilient and respond relatively quickly after a dam is removed.
“The apparent success of dam removal as a means of river restoration is reflected in the increasing number of dams coming down, more than 1,000 in the last 40 years,” said lead author of the study Jim O’Connor, geologist with the U.S. Geological Survey. “Rivers quickly erode sediment accumulated in former reservoirs and redistribute it downstream, commonly returning the river to conditions similar to those prior to impoundment.”
Dam removal and the resulting river ecosystem restoration is being studied by scientists from several universities and government agencies, including the USGS and U.S. Forest Service, as part of a national effort to document the effects of removing dams. Studies show that most river channels stabilize within months or years, not decades, particularly when dams are removed rapidly.
“In many cases, fish and other biological aspects of river ecosystems also respond quickly to dam removal,” said co-author of the study Jeff Duda, an ecologist with USGS. “When given the chance, salmon and other migratory fish will move upstream and utilize newly opened habitat.”
The increase in the number of dam removals, both nationally and internationally, has spurred the effort to understand the consequences and help guide future dam removals.
“As existing dams age and outlive usefulness, dam removal is becoming more common, particularly where it can benefit riverine ecosystems,” said Gordon Grant, Forest Service hydrologist. “But it can be a complicated decision with significant economic and ecologic consequences. Better understanding of outcomes enables better decisions about which dams might be good candidates for removal and what the river might look like as a result.”
Sponsored by the USGS John Wesley Powell Center for Analysis and Synthesis, a working group of 22 scientists compiled a database of research and studies involving more than 125 dam removals. Researchers have determined common patterns and controls affecting how rivers and their ecosystems respond to dam removal. Important factors include the size of the dam, the volume and type of sediment accumulated in the reservoir, and overall watershed characteristics and history.
Here’s the release from the United States Geological Survey:
Endocrine disrupting chemicals (EDCs) were transported 2 kilometers downstream of a wastewater treatment plant (WWTP) outfall in a coastal plain stream. EDCs persisted downstream of the outfall with little change in the numbers of EDCs and limited decreases in EDC concentrations.
U.S. Geological Survey (USGS) scientists measured concentrations of select EDCs approximately 10 times in water and sediment from 2009 to 2011, at five sites in the Spirit Creek watershed near Fort Gordon, Georgia, as part of an assessment of the effects of the closure of a WWTP on EDC persistence.
Sites included a control site upstream of the WWTP outfall and four other sites in the 2–kilometer reach extending downstream to Spirit Lake, into which Spirit Creek flows. A site located at the outfall of Spirit Lake was sampled once to assess the potential for EDC transport through the lake.
A modest decline (less than 20 percent in all cases) in surface-water detections of EDCs was observed with increasing distance downstream of the WWTP and was attributed to the chemicals attaching (partitioning) to the sediment. The EDCs focused on in this study included natural estrogens (estrone, 17β–estradiol, and estriol) and detergent metabolites, which exhibit estrogenic properties. Concentrations of estrogens and detergent metabolites downstream of the WWTP remained elevated above levels observed at the upstream control site, indicating that the WWTP was the prominent source of these chemicals to the stream. The mean estrogen concentrations observed downstream of the WWTP were 5 nanograms per liter and higher, a level indicative of the potential for endocrine disruption in native fish.
Estrogens were not detected in the outflow of Spirit Lake, indicating that they were diluted, partitioned to lake sediments, or were degraded within the lake through a combination of microbial processes and/or photolysis. However, detergent metabolites were detected in the outflow of Spirit Lake, indicating the potential for EDC transport downstream.
The ongoing post–closure assessment at the Fort Gordon WWTP will provide more insight into the environmental persistence of EDCs over time and the potential for stream and lake bed sediment to serve as a long–term source of EDCs in stream ecosystems.
The Fort Gordon Environmental and Natural Resources Management Office of the U.S. Army and the USGS Toxic Substances Hydrology Program provided the funding for this work.
More water pollution coverage here.