Can We Clean Up Our Waters?
Lessons from the Corsica River
On a hot Eastern Shore morning, biogeochemist Jeff Cornwell and geologist Cindy Palinkas set out in kayaks to paddle a small tributary of the Corsica River. Both scientists, who work at Horn Point Laboratory, played a key role in a collaborative research and synthesis effort aimed at understanding the fluxes of nutrients and sediments in the Corsica River.

MURKY WATER LAPS THE PAVEMENT at the Centreville Public Landing, enveloping Jeff Cornwell's sandal-clad feet. He's ankle deep, putting three kayaks into Mill Stream, a tributary of the Corsica River on Maryland's Eastern Shore.

The same water is more than calf-deep on Cindy Palinkas — she seems small and slight in contrast to Cornwell's 6-foot, 7-inch frame. Palinkas climbs into a red kayak, next to Cornwell's yellow one, and pushes off with the side of her paddle. The two scientists strike out toward the center of the stream.

It's a pretty morning on the Eastern Shore — skin-prickling hot and sunny, humming with the buzz of summer insects. Only the slice of the kayak paddle breaking the surface disturbs this quiet creek.

Cornwell and Palinkas have taken a morning away from Horn Point Laboratory, part of the University of Maryland Center for Environmental Science (UMCES). The kayak trip provides a welcome break from the logistics and hectic pace of usual field trips, when they go out to take sediment cores and conduct shipboard experiments. Paddling the Corsica River offers the scientists a rare opportunity to step back and reflect on the river they've studied for several years — and on its future.

A few feet from shore, Cornwell drives his paddle down into the streambed, stirring up muddy bottom. The water's less than two feet deep here, so his paddle doesn't go far. Bubbles burble to the surface — like a pot of water that's just reached its boiling point.

"Methane gas," he says. For Cornwell, a biogeochemist, this is evidence there's little to no oxygen in these bottom sediments. He explains that certain sediment-dwelling microbes produce methane when oxygen is scarce — a clear sign that anoxic or hypoxic processes are at work.

And not a good sign for the Corsica River.

Cornwell and Palinkas maneuver their kayaks upstream. As the creek narrows, the water grows shallower, just deep enough to keep the kayaks afloat. But even in mere inches of water, the river bottom is barely visible. No underwater grasses grow here. Algae and suspended sediments cloud the water, turning it the color of coffee with cream.

An Unprecedented Effort

In 1998, the degraded condition of the Corsica River system earned it a Category 1 designation by the state of Maryland in its Clean Water Action Plan — placing it on the list with highest priority for restoration. What followed was one of the most intensive, highly targeted restoration efforts ever mounted in the Chesapeake Bay watershed.

The Maryland Department of Natural Resources (DNR) and the Maryland Department of the Environment (MDE) developed restoration strategies for 25 watersheds across Maryland. These plans — called Watershed Restoration Action Strategies — offered a roadmap for restoration that combined a number of intensive best management practices, such as sewer and septic upgrades, stormwater management, and cover crops. Based on the strong restoration plan put forth in the Corsica, the state of Maryland in 2005 selected this watershed to launch an all-out cleanup effort.

Then-governor Robert Ehrlich made the project a centerpiece of his environmental agenda. "The Corsica River Pilot Project is the first of its kind in the Bay watershed and can provide a blueprint for the future restoration of the Chesapeake Bay watershed," he proclaimed when kicking it off in the spring of 2005. "This multi-faceted effort will demonstrate that with a focused approach, combined resources, and a comprehensive strategy, we can potentially restore an entire river system."

A bold statement. And an ambitious experiment. The state of Maryland made a five-year commitment to the tune of $19.4 million. This effort would require a massive push from diverse sectors, with dozens of public, private, and environmental partners coming together around a common goal — to restore one 6½-mile stretch of river, a small sub-watershed of the Chester River. If successful, it would become a proof of concept that might be replicated around the Chesapeake watershed.

Five years later, the Corsica remains on Maryland's list of impaired waterways under the Clean Water Act — receiving failing marks for excessive sediments, nutrient over-enrichment, PCBs, fecal coliform bacteria, and impacts to biological communities. Local governments and state agencies remain deeply engaged, but citizen buy-in won't last forever.

"We're doing all of these things and I think we are cleaning the river," says Jim Malaro, the president of the Corsica River Conservancy. "The major obstacle is that it is hard to show improvement," he says. "And it's hard to generate enthusiasm if we don't see improvement in the river."

With such a big investment and such a small return, more people are asking the tough question: What will it take — and how long will it take — to clean up the Corsica River?

What Can Data Tell Us?

The Corsica restoration effort began in 2005 with best management practices and monitoring. With a new focus on implementing best management practices on the ground, state and federal officials knew they would need to track water quality conditions very closely to find out whether their efforts were working.

All of a sudden, people were "running about the seascape and landscape of the Corsica making measurements," says Walter Boynton, an estuarine scientist from the UMCES Chesapeake Biological Laboratory. Volunteers from the Corsica River Conservancy were taking weekly samples from five stations in the river for water quality analysis. In a collaborative effort between DNR, the U.S. Geological Survey, and MDE, the agencies placed automated flow gauges just above where tidal influence begins in all three major streams that feed the Corsica. Together these gauges receive drainage from about 70 percent of the watershed, an unusually large fraction of a watershed to measure directly, says Boynton.

What they got were data. A lot of it.

To put it in perspective, just one of these automated sensor systems records dissolved oxygen and other variables every 15 minutes between March and October, generating a whopping 210,000 data points for each site, every year.

Agency representatives quickly realized that by themselves these large data sets don't provide meaningful information for management. So in 2006, the Maryland Department of Natural Resources tapped Boynton, who has studied the Chesapeake Bay for more than 30 years, to pull together a team of scientific collaborators for an intensive synthesis effort that DNR would largely fund. The resource managers, led by Resource Assessment Service director Bruce Michael and Corsica project coordinator John McCoy, issued Boynton a tough challenge. They asked him to use these vast data sets to create a nutrient budget, to predict whether the proposed restoration activities could reduce these loads if fully implemented.

They wanted a forecast: if nutrient loads came down, how would the Corsica River respond?

Walter Boynton (aka Labman) by Erica Goldman
Researcher Walter Boynton aboard the R/V Rachel Carson. Boynton pulled together a team of scientific experts to help assess the effect restoration efforts might have on the Corsica watershed. Credit: Walter Boynton.
Nutrient Overload

Boynton began by recruiting a top-flight group. He worked most closely with UMCES scientists Michael Kemp and Jeremy Testa, who have strong expertise in estuarine processes. He went to experts on stormwater from agencies and local governments and to experts on agriculture and cover crops from the Wye Center for Agro-ecology, especially Russ Brinsfield and Ken Staver. He also recognized the need to sample and account for certain processes not captured by ongoing measurements. For that, he turned to biogeochemist Jeff Cornwell to predict rates of denitrification and nitrogen burial in the Corsica River, both processes that can permanently remove nitrogen from the system. He looked to Cindy Palinkas to provide information about the overall sediment budget of the Corsica, to help understand the contribution of processes like shoreline erosion to the nutrient budget.

Boynton quips, "When the going gets tough, the smart collaborate."

By the spring of 2010, the scientific team was able to summarize their findings for DNR. Not surprisingly, their synthesis report found that nutrients from agriculture (so-called diffuse sources) make up the lion's share of the load entering the Corsica system — some 84 percent of the nitrogen and 74 percent of the phosphorus. The watershed's 25,298 acres are dominated by agricultural land uses — mostly corn and soybean farms that feed the Eastern Shore's poultry operations. Stormwater comes in a distant second, accounting for 10 percent of the nitrogen and 25 percent of the phosphorus (see Total Nitrogen Flux graph).

High nitrogen loads mean turbid water and algae blooms, says Boynton. Through further statistical analyses, the team demonstrated a strong relationship between the amount of nitrogen that reaches the system in the spring and the amount of chlorophyll-α (a proxy for algae) that shows up in summer. Algal blooms in turn reduce water clarity, letting very little light reach the bottom, despite the river's uniformly shallow depths. Currently, only 10 percent of the river bottom receives sufficient light to support even "potential" communities of underwater grasses, Boynton explains.

The team's study also confirms a strong connection between summer chlorophyll-α concentrations (algae) and low oxygen conditions (hypoxia). To generate this statistical relationship, they analyzed data from multi-probe sensor systems that recorded variables such as dissolved oxygen, chlorophyll, and turbidity at three different sites every 15 minutes between March and October of each year.

That high nutrient concentrations lead to poor water clarity and hypoxic conditions is not surprising. This is a story that's been repeated from tributary to tributary all over the Chesapeake watershed. But the connection between springtime nitrogen and summertime chlorophyll does carry a surprising twist. The relationship between nitrogen loading and chlorophyll-α is what scientists call "non-linear" (see Benefits of Reduced Nitrogen Load graph). In this case that non-linear connection means that small declines in nitrogen loading might lead to large declines in algae blooms.

Thanks to this connection, the Corsica River estuary currently hovers near a potential "tipping point" for nitrogen loading, explains Boynton. And it's a tipping point in the right direction. Nutrient reduction efforts could really punch a lot of bang for the buck, he says. To put it in numbers, the data suggest that a 50 percent reduction in nitrogen loading to the system would produce a 70 percent decline in summer algae.

Crossing this threshold would push the Corsica River toward another one — a tipping point that would cause a rapid increase in water clarity up to 75 percent. Here non-linearity becomes important again, explains Boynton. A relatively small change in water clarity (Secchi depth increase by about half a meter) is predicted to cause a sharp increase in the amount of river bottom that would receive enough light to support the growth of benthic algae and underwater grasses — critical for repairing degraded ecosystem functions in the Corsica River. Their predictions also suggest that a 50 percent reduction in nitrogen load and an associated chlorophyll-α decline would also reduce the amount of summer low oxygen by 80 percent, essentially eliminating the water quality problem.

These potential tipping points or thresholds for nitrogen loads, algal abundance, and water clarity are good news for the Corsica River says Boynton. But will nutrient loads decline enough to cause the river to "tip"?

Land use map
Agriculture for corn and soybeans (shown on map in yellow), dominates the Corsica watershed, making up more than 60 percent of the land cover. Outside the town of Centreville, the population in the watershed is spread out, with developed land comprising a relatively small overall percentage. Map courtesy of the Maryland Department of Natural Resources.
Benefits of Reducing Nutrients
To create a nutrient budget for the Corsica River, researchers evaluated nitrogen inputs and losses from all sources. They were not surprised to find that most of the nitrogen entering the watershed comes from agriculture.
Benefits of Reducing Nutrients
Benefits of Reducing Nutrients
Scientific models predict that a 50 percent reduction in nitrogen loads would increase water clarity enough to significantly boost bottom habitat for plants and decrease hypoxia (bottom left). Improving light penetration (measured by Secchi disk) from 0.7 meter to 1.2 meter, for example, would lead to a sharp increase in the amount of light reaching the bottom (maps at right). Graphs and maps (bottom right) courtesy of Walter Boynton.
Putting Science to Work

For citizens of the watershed, getting the Corsica River to the tipping point is serious business. The county government employs a watershed planner, Eva Kerchner, who oversees all of the stormwater retrofit projects. Since September 2009, she has managed the construction of a three-quarter-acre wooded wetland that drains 17 acres of the watershed within town boundaries. She's overseen the relocation of storm drains to intercept the drainage from impervious surfaces that were directly discharged into Gravel Run, one of the Corsica's small tributaries. She's also managed a retrofit project for 10 acres of drainage area to a coastal plain outfall, reconfiguring a pipe that dumped stormwater directly into the stream.

Along with multiple partners, the town of Centreville also has instituted a Green Business Certification, offering a voluntary program whereby businesses that follow a stringent set of best management practices can market their participation with a sticker displayed in their storefront window. To date, Centreville boasts 11 certified green businesses, restaurants, and office spaces — including big retail operators such as Acme and Food Lion.

Watching over these governmental projects is the non-governmental Corsica River Conservancy, some 670 members strong, working to build stakeholder buy-in for the restoration process. Volunteer members coordinate weekly water quality sampling in the summer months, a process done with scientific rigor sufficient to be included with the Chesapeake Bay Program's water quality sampling data (see A Citizen Scientist).

Symphony Village
rain garden
John McCoy
demonstration rain garden
The Corsica River watershed boasts some 250 rain gardens — an impressively high number for a watershed with only about 1600 families. Rain gardens help retain stormwater, preventing direct runoff into creeks. The over-55 community of Symphony Village has nearly 70 rain gardens (top), and the Centreville Public Library is home to a large demonstration rain garden (bottom left) with explanatory signage. Standing near the headwaters of Gravel Run, John McCoy, who helped coordinate the Corsica restoration effort for the Maryland Department of Natural Resources, checks on one of three automated water samplers.

The Corsica River Conservancy also facilitates the installation of rain gardens in Centreville, acting as liaisons between the homeowner and contractor. They help administer a grant that provides $2,000 per homeowner to offset the installation and material costs. The practice of planting rain gardens seems to have spread like wildfire, says John McCoy, who has overseen the coordination of the Corsica River restoration effort since the beginning for Maryland DNR. The town of Centreville now boasts nearly 250 rain gardens, with dozens more in the planning stages.

Outside of town, the Corsica River Conservancy and Maryland DNR have undertaken extensive wetland restoration and planting of forested buffers in places like Bloomfield Farm — a large property owned by the county on the outskirts of town. The group also oversees the Maryland Grows Oysters project for the watershed, which has put 140 cages in the water for oyster aquaculture.

These efforts have clearly improved the local environment and bolstered on-ground capacity for restoration. But frankly, it would be surprising if citizens could see an improvement in the river at this point. Aside from the upgrade to the sewage treatment plant, which brought about an initial 7 to 8 percent decline in nitrogen, nutrient loads have not yet decreased by even a measurable amount, says McCoy.

"The [synthesis] report is spot on as far as what needs to be done," he says. "We haven't achieved this yet, but it confirms and reaffirms what we need to do. I don't think people really appreciate how much work needs to get done to really improve water quality."

So what will it will it take to reduce nutrient loads in the Corsica? That is the million-dollar question.

Centerville, Va
Bloomfield Farm
Thanks to the Corsica River Restoration Pilot Project, the town of Centreville (left) is home to sewer, septic, and stormwater upgrades, along with hundreds of rain gardens. On the outskirts of town, Bloomfield Farm (above), a property owned by Queen Anne's County, has become a demonstration site for wetland and meadow restoration, as well as forest buffers and cover crops.
Cover Crop Challenge

In the drive to reach a positive tipping point for the Corsica, the greatest roadblock facing the watershed is nutrient runoff. "If we can't get a handle on agricultural pollution, we won't get anywhere," says the Corsica River Conservancy's Malaro. "All of the other things that we are doing pale in comparison."

But solving the problem related to nutrient pollution from agriculture presents huge challenges. Crops like corn and soybeans depend on nitrogen-based fertilizers for rapid growth. As long as these crops drive the economy of the Eastern Shore, high nutrient loads will be on the ground.

When the summer growth season ends, these annual crops die back. At this point, active uptake of water and nitrogen (in the form of nitrate) cease, though soil processes that release nitrate will continue as long as soil temperatures are warm.

Fall and winter become vulnerable seasons for nutrient pollution. Freely available nitrate in the soil can flow directly into nearby ditches and creeks when it rains, ultimately making its way into the river. Winter rain and snowmelt also seep downward through surface soils toward the groundwater — carrying with them any nitrate that was left in the root zone. Nitrogen that reaches the groundwater can be trapped in the system for up to 10 years, according to a study by the U.S. Geological Survey.

Planting cover crops ranks as the best way to reclaim the nitrogen and phosphorus applied to farm fields. "We get the biggest bang for the buck with the cover crop program," says Dave Mister, who's served as the Eastern Shore area supervisor for the Maryland Department of Agriculture for nearly 23 years. And not just for the Corsica, but for the entire state of Maryland.

Cover crops can keep nutrients from leaving the farm, explains Mister. If planted early enough, these crops — small grains such as rye or barley or winter wheat planted without fertilizers immediately after harvesting corn or other row crops — also help take up nitrate in the root zone before it leaches into groundwater.

In the Corsica watershed, total crop acres approach 11,000 acres. Under the restoration scenario, the goal acreage for cover crops is 6,000 acres, or roughly 60 percent.

This is high, says Mister. On a year-to-year basis, he doesn't think that 60 percent is an attainable goal. "Weather is a big factor," he says. "Last fall was just horrendous. We're lucky to have gotten the cover crops that we did get planted."

"I would like to see a 30-35 percent goal. "I think this is reasonable for farmers to accommodate in this watershed, but this is probably not enough from a nutrient reduction standpoint."

Dave Mister and Katie Staff by Erica Goldman
A farmer plants cover crops by National Resources Conservation Service
At the county office for the MDA Soil Conservation District, area supervisor Dave Mister and soil conservation planner Katie Starr look over a map showing farms in the Corsica watershed (left). In the fall, farmers plant cover crops, like barley (right), to prevent excess nutrients from polluting local streams and seeping into groundwater. Farmer planiting barley courtesy of the Maryland Department of Natural Resources.

Though incentives help, planting and managing additional cover crop acreage is hard work for farmers. "This is where we struggle," says Mister. "Farmers understand that cover crops will help the Bay, but it all comes down to how much one individual can do."

This year, MDA has made some strategic changes to the cover crop program statewide to boost acreage enrollment. For the first time, the agency removed the acreage cap, which previously set a limit on how many acres an individual farmer could plant. While the intent of the cap had been to ensure that incentive payments were distributed equitably, Mister suspected that the cap was holding back individual farmers from planting their maximum possible cover crop acreage. In addition, MDA extended the window for cover crop signup — increasing the period from one week to three.

TALL STANDS OF CORN arc high along the sides of the road, like walls of a slot canyon. Our car navigates the narrow passage until we reach a grassy clearing. Here Buck Morris waits alongside his black pickup truck, near the property line where his farm extends toward busy Route 213. more . . .

The Maryland Department of Agriculture also stepped up outreach to farmers for the cover crop program in the Corsica watershed. The agency advertised in the newspaper and placed huge signs up at the field mills, so farmers would see them when they were hauling in wheat to sell. Katie Starr, the soil conservation planner for the Queen Anne's County Soil Conservation District, sent letters and contacted each farmer in the watershed by phone to explain the program — some multiple times. She offered to come out to the farm to sign anyone up if they were too busy to make it into the Soil Conservation District office, since the signup period fell during the window for wheat harvest. Buck Morris, a farmer who works land for ten different landlords in the watershed, took her up on the offer (see View From the Farm). She enrolled him in the cover crop program while riding with him on his combine.

MDA's efforts seem to be working. Whether due to the change in acreage cap or intensified outreach, cover crop enrollment has hit a peak this year, both in the Corsica and throughout the state. For 2010-2011, the Corsica watershed has enrolled more than 9,000 acres in the program, for the first time both meeting and exceeding the 60 percent target. Compared with last year, more than twice as many farmers enrolled more than double the previously enlisted acreage. Statewide, MDA approved a record 502,323 acres of cover crops, requested by 1,688 farmers.

The Gift of Time

Cover crops, stormwater management, sewage treatment and septic upgrades, wetland restoration, riparian buffers. The Corsica watershed has made considerable progress toward getting these best management practices in the ground. In doing so, they've created a solid foundation of local capacity for restoration and deep community engagement. No doubt that these efforts have improved the local environment in real and tangible ways. But will these efforts ultimately translate to an improvement in water quality?

"People look to Corsica for how to accomplish things and for lessons learned," says McCoy, who recently left his coordinating role with DNR to take a job as watershed planner with the Columbia Association in Howard County. "How much work it will take is one of the lessons learned."

Hard work and time. This seems to be the verdict on what it will take to restore the Corsica River. In preparing the synthesis report, Boynton reviewed the calculations in his statistical models with agriculture experts. The calculations suggest that the watershed still needs to do a lot of cover cropping — early planting, year in and year out, to really achieve reductions in nutrient loads. It will take time, he says. Nitrogen that seeps into the ground can reside in groundwater for more than a decade. Once enough cover crops are in the ground, one could still expect a lag time of anywhere from five to eight years for nutrient loads to actually decline.

With aggressive cover cropping, combined with continued upgrades to septic systems and stormwater treatment, models predict that a 50 percent target for nitrogen load reduction could be achieved. And the good news is that once nutrient loads do come down, recovery should be fairly rapid. The "tipping point" effect predicted by the team's study suggests that once the algae-clouded water begins to clear and light can reach the bottom, ecological processes should kick in to take the river the rest of the way.

But will funding and politics stay the course for the Corsica River? Boynton for one has his doubts. "If political officials lasted for the residence time of groundwater, maybe they'd support this," he said in a symposium talk in which he presented the report's findings.

THE SMALL BOAT ROCKS GENTLY as Sandy Simpson fits a glass sample bottle into a metal buckle at the end of a long wooden pole. She unseals the cap and lifts the pole over the side of the boat as it idles along the widest part of the Corsica River. Leaning down, she swipes the bottle through the water, making sure that the sample comes from below the surface. more . . .

And the Corsica River restoration pilot project raises a big question for the Bay as a whole. If it takes so much to bring back one 6½-mile stretch of river, what will it take to replicate such intensive efforts tributary-by-tributary over the whole Chesapeake Bay watershed?

This question comes at a time when the stakes are higher than ever. This summer, the Environmental Protection Agency adopted nutrient and sediment goals that represent the maximum amounts of nitrogen, phosphorus, and sediment that can originate river-by-river from each state, so-called Total Maximum Daily Loads or TMDLs (see What Will It Take to Limit "Daily Loads"?). These will be legally binding requirements, a huge pressure on local jurisdictions watershedwide.

As Bay states move forward into the brave new world of TMDLs, the Corsica River carries an important message for the future. Restoration takes time, money, and a whole lot of hard work. The best science available predicts that the Corsica River can recover, and rebound quickly, once nutrient loads come down. But it will take a marathon, not a sprint, to achieve a tipping point for recovery in this watershed. The road to restoration will be a steep hill to climb.

vol. 9, no. 3
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