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Bay Blog: Conowingo Dam

Aug
03
2016

Photo Essay: Seen from above, humans and nature intertwine along the Chesapeake Bay

The Bird River flows into the Gunpowder River in Baltimore County, Maryland, on June 27, 2016. The 26-square-mile Bird River watershed is about one-third forested land and one-fifth agricultural land. It received Baltimore County's first comprehensive watershed plan in 1995 to address water quality issues caused by unstable stream channels, impervious surfaces, pollutants, mining, agriculture and other threats. Today, completed stream restoration along the mainstem and tributaries of Bird River total five miles.

Flying low over the Chesapeake Bay, it’s not actually the water that draws your attention—except for the sporadic glint of sunlight reflected off of its calm surface. Instead, it’s the patchwork landscape and the rate at which a quiet farm field gives way to grids of streets or wriggling stretches of wetlands.

And there’s another reason to pay attention to all that land: because the Chesapeake Bay is so shallow—its average depth is just 21 feet—and because so much land area feeds into it, the health of the Bay depends greatly on how the land is treated.

With the support of a volunteer pilot from the nonprofit organization LightHawk, we took a look around the northern edges of the Chesapeake Bay to see some of the ways the land has been shaped by the people living there.

The Susquehanna River flows south past Conowingo Dam, toward Havre de Grace, Maryland. Conowingo Dam has long trapped sediment runoff originating from farms and other sources upstream. But as the dam nears 100 years of age, its capacity for trapping sediment is now at equilibrium, meaning it can only trap sediment in the short-term, after heavy storms scour away some of the buildup behind the dam.

Maryland Route 301, known as Blue Star Memorial Highway, runs toward Queenstown, Maryland. An effort by the Eastern Shoreway Alliance (ESA) to get the stretch of highway designated a scenic byway stalled ten years ago. In the group's proposal, quoted in the Chestertown Spy news website, the ESA describes the area surrounding 301 as a "slowly woven tapestry of exceptionally rich farm fields and pastures, natural woodlands and meadows, tidal estuaries and marshes.”

Skipton Creek flows west into the Wye River in Talbot County, Maryland. The Wye River received a "C" grade overall in the Midshore Riverkeeper Conservancy's 2015 report card—the same grade as in 2014—with phosphorus pollution in the "D" to "D-" range.

A patch of forest is shaped by the manicured fields surrounding it near the Elk River in Cecil County, Maryland. As trees have been replaced with roads, buildings, farms and houses, 60 percent of the Chesapeake Bay watershed’s forests have been divided into disconnected fragments. This increases the amount of sun-exposed forest "edge"—where fields and forest meet—that favors invasive species and large populations of deer.

A recently planted riparian forest buffer borders an agricultural field along Emory Creek, which flows into the Corsica River in Queen Anne's County, Maryland. A lack of buffers is a major challenge for the restoration of the Corsica, according to the river's Watershed Restoration Action Strategy (WRAS) completed in 2004.

Chicken barns rise from a farm in Queen Anne's County, Maryland. Manure accounts for 19 percent of the nitrogen and 26 percent of the phosphorus entering the Chesapeake Bay, according to a 2010 report by the U.S. Environmental Protection Agency.

Poultry, corn, and soybeans are the dominant agriculture on the Eastern Shore currently, but industries have gone through boom-bust cycles on the Delmarva Peninsula since the early 1600s. Retirees, commuters and tourists have increased their footprint since travel became easier with opening of the Chesapeake Bay Bridge in 1952.

Box stores and townhouses spread through a suburban area of Easton, Maryland. The opening of the Chesapeake Bay Bridge in 1952 made travel to the Eastern Shore more convenient, literally paving the way for rapid population growth in the 1990s and early 2000s. The town of Easton grew by over one third between 1990 and 2003.

The 13.6-megawatt Wye Mills solar project features over 40,000 solar panels on 97 acres in Queen Anne's County, Maryland. The project, to be online in 2016, is set to deliver energy to Johns Hopkins University, which chose the remote site because of a lack of space near its campus in Baltimore.

Baltimore's Inner Harbor is seen at the far left at the end of the northwest branch of the Patapsco River, which receives water from the mouth of Jones Falls. The Inner Harbor and tidal Patapsco River have received failing water quality grades for years, according to a report card published by the Healthy Harbor Initiative for the Waterfront Partnership of Baltimore.

Riprap and bulkheads harden a shoreline along Edgemere, Maryland, near North Point State Park in Baltimore County. Hardened shorelines eliminate the shallow habitat required by many of the small fish and invertebrates that trophy fish like striped bass eat, and can also make it hard for underwater grasses to take root in the turbulent waves reflected off the hard surface.

Patterson Park offers the only green space to much of the surrounding neighborhoods in Baltimore.

Hart-Miller Island State Park lies east of Baltimore in the Chesapeake Bay. The 1,100-acre island began as two distinct islands joined by dredged material in a restoration project overseen by Maryland Environmental Service. In 2016, the 300-acre south cell of the island opened to the public for the first time since the U.S. Army Corps of Engineers began dredging in 1981.

Wetlands flow into the Chesapeake Bay near the mouth of the Elk River in Cecil County, Maryland. Aberdeen Proving Ground, northeast of Baltimore, is visible in the distance. Shoreline development poses a major threat to wetland, but protected areas like Elk Neck State Park help protect portions of these habitats from destruction.

To view more photos, visit the Chesapeake Bay Program's Flickr page

Photographs and text by Will Parson

Will Parson's avatar
About Will Parson - Will is the Multimedia Specialist for the Chesapeake Bay Program. A native of Bakersfield, California, he acquired an interest in photojournalism while studying ecology and evolution at University of California, San Diego. He pursued stories about water and culture as a graduate student at Ohio University's School of Visual Communication, and as an intern at several newspapers in New England before landing in Maryland.



Mar
10
2016

Upstream pollution reductions could ease effects of Conowingo Reservoir infill, report maintains

Reducing pollution in the Susquehanna River watershed could ease the environmental effects of an essentially full reservoir behind Conowingo Dam, according to a final report from the Lower Susquehanna River Watershed Assessment (LSRWA) team released today.

For decades, the reservoir behind Conowingo Dam—as well as those behind the Holtwood and Safe Harbor dams—has trapped particles of sediment flowing down the Susquehanna River, along with the nutrients that are often attached. But a draft report from the LSRWA team released in November 2014 indicated this reservoir is full—and the final report upholds these findings: no substantial changes were made to the findings or recommendations of the report between the draft and final phases.

According to the report, the reservoir is trapping smaller amounts of sediment and nutrients and, during large storms, sending more of these pollutants into the Susquehanna River more often. The report indicates that reducing pollution loads, particularly nutrients, upstream of the dam would provide a more effective solution than various strategies for managing sediment at the dam itself, such as dredging or bypassing.

In 2010, the Chesapeake Bay Total Maximum Daily Load (TMDL) was established to reduce nutrient and sediment loads across the watershed. Bay jurisdictions—Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia and the District of Columbia—and federal agencies are currently in the process of submitting draft two-year water quality goals, or milestones, to achieve the nitrogen, phosphorus and sediment reduction goals of the TMDL.

The final report is available on the LSRWA website.



Feb
27
2015

Sediment in Conowingo reservoir exceeds 90 percent of storage capacity

Sediment building up behind Conowingo Dam has almost reached the reservoir’s capacity for storage, according to a report released by the U.S. Geological Survey (USGS). The reservoir is considered at its limit for holding sediment when it is half full—at present, it is 92 percent of the way toward this maximum.

The reservoir behind Conowingo Dam, which traps sediment and nutrients flowing down the Susquehanna River, has reached 92 percent of its capacity for storage.

Since its construction in 1929, the Conowingo reservoir, along with the reservoirs behind the Holtwood and Safe Harbor dams, has trapped sediment and nutrients as they flow down the Susquehanna River—which provides nearly half of the fresh water that flows into the Bay. According to the report, the ability of these reservoirs to trap pollutants has been steadily declining.

“Storage capacity in Conowingo reservoir continues to decrease, and ultimately that means more nutrients and sediment will flow into the Bay,” said Mike Langland, author of the study, in a release. “Understanding the sediments and nutrients flowing into the Bay from the Susquehanna River is critical to monitoring and managing the health of the Bay.”

Excess sediment can cloud the water and harm underwater grasses, fish and shellfish, while nutrients can fuel the growth of harmful algae blooms and the creation of low-oxygen “dead zones,” which suffocate underwater life. Reducing the amount of pollutants in local waterways is integral to Bay restoration efforts, including the Chesapeake Bay Total Maximum Daily Load (TMDL), or “pollution diet,” which Bay Program partners recommitted to achieving as part of the Chesapeake Bay Watershed Agreement. In anticipation of a decline in Conowingo reservoir’s ability to trap sediment, the TMDL includes a mechanism for addressing any increases in nutrient and sediment pollution caused by a full reservoir.

The report from USGS reiterates the findings of a study by the Lower Susquehanna River Watershed Assessment (LSRWA) team, released in November 2014, which found that the once-effective “pollution gate” is trapping smaller amounts of sediment and nutrients and, during large storms, sending more of these pollutants into the Susquehanna River more often. The team found that reducing pollution loads upstream of the dam would pose a more effective solution that dredging, bypassing or other operational changes, which would come with high costs and low or short-lived benefits.

The USGS report, Sediment Transport and Capacity Change in Three Reservoirs, Lower Susquehanna River Basin, Pennsylvania and Maryland 1900–2012, is available online.



Nov
13
2014

Reducing upstream pollution could ease effects of full Conowingo reservoir

A team of scientists has found that reducing pollution in the Susquehanna River watershed—which includes portions of New York, Pennsylvania and Maryland—could ease the environmental effects of an “essentially full” reservoir behind the Conowingo Dam, whose pollution-trapping capacity has diminished in recent years.

The reservoir behind the Conowingo Dam—as well as those behind the Holtwood and Safe Harbor dams—has for decades trapped particles of sediment flowing down the Susquehanna River, as well as the nutrients that are often attached. But according to research from the Lower Susquehanna River Watershed Assessment (LSRWA) team, this reservoir is full. The once-effective “pollution gate” is trapping smaller amounts of sediment and nutrients and, during large storms, sending more of these pollutants into the Susquehanna River more often.

While researchers explored strategies for managing sediment at the dam, the team found that reducing pollution loads upstream of the dam would pose a more effective solution to the “full reservoir” problem. Indeed, dredging, bypassing or other operational changes would come with high costs and low or short-lived benefits. But adhering to the Chesapeake Bay’s “pollution diet”—and taking additional steps to reduce pollution where possible—would offer management flexibility and environmental benefits.

The Chesapeake Bay Total Maximum Daily Load (TMDL) was established in 2010 to reduce nutrient and sediment loads across the watershed. Lowering these pollutants is integral to restoring the health of the Bay: excess sediment can cloud the water and harm underwater grasses, fish and shellfish, and nutrients can fuel the growth of harmful algae blooms. While the LSRWA team did find that the effects of the sediment that “scour” from the Conowingo reservoir cease once it settles to the bottom of the river, the effects of nutrient pollution linger. Green infrastructure, forest buffers and sound farm and lawn management can help businesses, landowners and individuals contribute to a restored Chesapeake.

Learn more.



Aug
30
2012

Sediment reservoirs in lower Susquehanna reach capacity, deliver more pollutants into Bay

Sediment reservoirs near the mouth of the Susquehanna River are filling up faster than researchers expected, posing a new obstacle for improving water quality in the Chesapeake Bay. 

As the holding areas behind the lower Susquehanna's three dams reach capacity, their ability to trap upriver sediment and the phosphorous that is often attached wanes, and the sediment that is held grows more and more likely to flow out of the reservoirs and into the river.

Image courtesy Jane Thomas/Integration and Application Network/University of Maryland Center for Environmental Science.

According to a report released by the U.S. Geological Survey (USGS), strong storms, severe flooding and faster-moving water have turned the one-time pollutant blockers into less effective gates.

The Susquehanna delivered more phosphorous and sediment into the Bay last year than it has in more than three decades of monitoring. The past 15 years have seen a 55 percent increase in phosphorous entering the Bay from the river and a 97 percent increase in sediment. And while nitrogen flow has dropped, it shows a jump during large storms--like Tropical Storm Lee in 2011 or Hurricane Ivan in 2004--and the flooding that follows.

Excess nutrients and sediment can harm fish, shellfish and underwater grasses. Nitrogen and phosphorous fuel the growth of algae blooms that rob water of oxygen and, with suspended sediment, cloud the water and block the sunlight that plants need to grow.

A previous USGS report cited improvements in nutrient and sediment trends as a sign of improving Bay health. The USGS has seen significant reductions in nutrient and sediment concentrations upstream of the reservoirs, which reflect the positive impacts of conservation efforts in the Susquehanna watershed. But the filling reservoirs behind the Safe Harbor and Holtwood dams in Pennsylvania and the Conowingo Dam in Maryland overshadow the pollution reduction progress that is being made.

The Lower Susquehanna River Watershed Assessment team, composed of federal, state and regional partners and administered by the U.S. Army Corps of Engineers, is exploring ways to expand the reservoirs' capacity. 

Learn more about the flow of nitrogen, phosphorous and suspended sediment from the Susquehanna River into the Bay



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