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Bay Blog: groundwater

Feb
25
2014

Science shows restoration work can improve local water quality

Pollution-reducing practices can improve water quality in the Chesapeake Bay and have already improved the health of local rivers and streams, according to new research from the Chesapeake Bay Program partnership.

In a report released today, several case studies from across the watershed show that so-called “best management practices”—including upgrading wastewater treatment technologies, lowering vehicle and power plant emissions, and reducing runoff from farmland—have lowered nutrients and sediment in local waterways. In other words, the environmental practices supported under the Clean Water Act, the Clean Air Act and the Farm Bill are working.

Excess nutrients and sediment have long impaired local water quality: nitrogen and phosphorous can fuel the growth of algae blooms and lead to low-oxygen “dead zones” that suffocate marine life, while sediment can block sunlight from reaching underwater grasses and suffocate shellfish. Best management practices used in backyards, in cities and on farms can lower the flow of these pollutants into waterways.

Data collected and analyzed by the Bay Program, the University of Maryland Center for Environmental Science (UMCES) and the U.S. Geological Survey (USGS) have traced a number of local improvements in air, land and water to best management practices: a drop in power plant emissions across the mid-Atlantic has led to improvements in nine Appalachian watersheds, upgrades to the District of Columbia's Blue Plains Wastewater Treatment Plant have lowered the discharge of nutrients into the Potomac River and planting cover crops on Eastern Shore farms has lowered the amount of nutrients leaching into the earth and reduced nitrate concentrations in groundwater.

“In New Insights, we find the scientific evidence to support what we’ve said before: we are rebuilding nature’s resilience back into the Chesapeake Bay ecosystem, and the watershed can and will recover when our communities support clean local waters,” said Bay Program Director Nick DiPasquale in a media release.

But scientists have also noted that while we have improved water quality, our progress can be overwhelmed by intensified agriculture and unsustainable development, and our patience can be tested by the “lag-times” that delay the full benefits of restoration work.

“This report shows that long-term efforts to reduce pollution are working, but we need to remain patient and diligent in making sure we are putting the right practices in place at the right locations in Chesapeake Bay watershed,” said UMCES President Donald Boesch in a media release. “Science has and will continue to play a critical role informing us about what is working and what still needs to be done.”

UMCES Vice President for Science Applications Bill Dennison echoed Boesch’s support for patience and persistence, but added a third P to the list: perspiration. “We’ve got to do more to maintain the health of this magnificent Chesapeake Bay,” he said.

“We’ve learned that we can fix the Bay,” Dennison continued. “We can see this progress… and it’s not going to be hopeless. In fact, it’s quite hopeful. This report makes a good case for optimism about the Chesapeake Bay.”

You can view an Executive Summary of the report here. Learn more.



Dec
11
2013

Groundwater withdrawal causing land to sink in lower Chesapeake region

The intensive withdrawal of groundwater is causing land to sink in the lower Chesapeake Bay region, worsening the effects of sea-level rise and increasing the severity of floods along the Delmarva Peninsula and Virginia Coastal Plain.

Image courtesy PhotoSeoul/Flickr

Land subsidence, or the sinking of the land’s surface, is in part a natural phenomenon, occurring as bedrock responds to the melting of an ice sheet that once covered Canada and the northern United States. But according to a new report from the U.S. Geological Survey (USGS), most of the land subsidence in this area is taking place in response to groundwater withdrawal, which could help explain why the region has the highest rates of relative sea-level rise on the Atlantic Coast.

When groundwater is pumped out of the earth, water levels in the area’s underground aquifers decrease. As these water levels decrease, the aquifer system compacts, causing the land above it to sink. In the southern Bay region, land subsidence has been measured at rates of 1.1 to 4.8 millimeters per year—close to the width of five stacked pennies.

Land subsidence can increase flooding, alter wetland and coastal ecosystems, and damage human infrastructure and historical sites. Some areas in Virginia—like the city of Franklin and the counties of Isle of Wight and Southhampton—have already experienced floods as the land around them sinks, and the low-lying Hampton Roads could experience similar episodes soon.

But according to the USGS, a change in water use—from moving groundwater pumping out of high-risk areas to slowing rates of groundwater withdrawal—could slow or mitigate land subsidence and relative sea-level rise.

Learn more.



Nov
12
2013

Ancient seawater found under Chesapeake Bay

The oldest body of seawater ever identified is buried under the Chesapeake Bay.

According to the U.S. Geological Survey (USGS), this recently discovered body of water dates back to the Early Cretaceous period, when wet and dry seasons controlled the climate, tropical jungles dominated the landscape and dinosaurs were becoming more plentiful.

Image courtesy Nicolle Rager-Fuller/National Science Foundation

The water is buried beneath a large meteorite that struck the earth 35 million years ago, throwing debris into the atmosphere and spawning a train of tsunamis that probably reached as far as the Blue Ridge Mountains. The so-called “Chesapeake Bay impact crater” is the largest crater discovered in the United States and helped determine the current shape of the Bay.

Because the water is trapped in place, USGS scientists have been able to estimate its age—100 to 145 million years old—and its salinity—twice as salty as modern seawater.

Acting USGS Associate Director for Water Jerad Bales said in a media release that before this discovery was made, no one realized that the saltier-than-normal groundwater found deep in the Atlantic Coastal Plain “was North Atlantic ocean water that has essentially been in place for 100 million years.”

“We are working directly with seawater that dates far back in earth’s history,” Bales said.

Learn more.



Nov
12
2013

Groundwater pushes nitrogen into Bay, delays effects of restoration

Slow-moving groundwater on the Delmarva Peninsula could push excess nutrients into the Chesapeake Bay even after we have lowered the amount of nitrogen and phosphorous we put onto the land.

Image courtesy yorgak/Flickr

According to new research from the U.S. Geological Survey (USGS), most of Delmarva is affected by the slow movement of nutrients from the land into the water. A USGS model developed to track the movement of nitrogen through the region showed that groundwater—and the pollutants it can contain—takes an average of 20 to 40 years to flow through the peninsula’s porous aquifers into rivers and streams. In some parts of Delmarva, the groundwater that is now flowing into local waterways contains nitrogen linked to fertilizer used three decades ago.

The slow flow of nitrogen-laden groundwater into the Bay could affect efforts to restore the watershed, lengthening the “lag-time” between the adoption of a conservation practice and the effect of that practice on a particular waterway. In other words, it could take days or even decades for today's management actions to produce positive water quality results.

“This new understanding of how groundwater affects water-quality restoration in the Chesapeake Bay will help sharpen our focus as many agencies, organizations and individuals work together to improve conditions for fish and wildlife,” said Lori Caramanian, Department of the Interior Deputy Assistant Secretary for Water and Science, in a media release.

While these findings seem to contradict the value of our restoration work, the study in fact indicates that pollution-reducing practices put in place over the past decade have begun to work. The study also confirms that rigorous steps taken to reduce nutrients on the land will lower the amount of nitrogen loading into streams in the future.

Learn more.



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