Editor’s note: This is part of a series of articles examining issues related to the Cheaspeake Bay Program’s “Midpoint Assessment” of Chesapeake cleanup efforts.

Information on the Nutrient and Sediment Trend tables shown in the image box above is provided here.

Take one Conowingo Dam, sprinkle it with a bit of climate change, mix in an unhealthy amount of phosphorus-saturated soil and you could have the recipe for a big Bay headache.

Those are some of the major science and policy issues that local, state and federal officials are grappling with as they take stock of where Chesapeake Bay cleanup efforts stand with the halfway mark approaching in the agreed-upon timetable for reaching restoration goals.

For several years now, officials have been preparing for what’s known as the “midpoint assessment,” mulling over new science, monitoring data, land use and other local information to gauge the effectiveness of actions taken to date. And perhaps even more importantly, they’re trying to understand what’s changed since the latest Bay cleanup goal was set in 2010.

The goal of the assessment, slated for completion next year, is to use all available new information to make whatever adjustments are needed to complete the multi-billion dollar restoration effort by its 2025 deadline. Based on the results, states and the federal agencies will need to revise their strategies for delivering a healthy Bay for the public — as well as for the crabs, fish, underwater grasses and even bottom-dwelling worms that depend on it.

The good news is that a wealth of new information is providing a clearer-then-ever picture of where pollution is coming from and how it’s affecting the nation’s largest estuary. On the other hand, that information, when melded together, is likely to show that meeting nitrogen, phosphorus and sediment reduction goals by 2025 will be a more daunting task than what was envisioned just a few years ago.

“I feel fairly confident that the level of effort is going to have to increase, and likely increase substantially,” said James Davis-Martin, Bay coordinator with the Virginia Department of Environmental Quality and chair of the state-federal Bay Program’s Water Quality Goal Implementation Team. But exactly how much harder the cleanup could be, Davis-Martin said, “is still unknown.”

The midpoint assessment was required as part of the “accountability framework” of the Chesapeake Bay Total Maximum Daily Load, or TMDL, when it was established by the Environmental Protection Agency in 2010, setting enforceable limits on the key pollutants fouling the Bay’s waters: nitrogen, phosphorus and sediment.

Taking note of previously missed cleanup deadlines, the EPA set a series of interim deadlines to keep efforts on track, including a 2017 goal that called for taking actions sufficient to achieve 60 percent of the pollutant load reductions needed for a clean, healthy Bay. That would have put the region on a glide path toward meeting its overall 2025 cleanup goal, with eight years to achieve the remaining 40 percent pollution reductions.

Since 2010, nutrient and sediment levels reaching the Bay have fallen. Wastewater treatment plants are proving to be capable of removing more nutrients than earlier thought, and states are slowly ramping up programs to control stormwater and agricultural runoff.

But the most recent data released by the EPA in April show that the region will almost certainly miss its 2017 nitrogen interim target, and is not on pace to meet sediment goals.

Further, many shortfalls are in critical places. About 75 percent of the nitrogen reductions since the TMDL was imposed have come from wastewater plants, which disproportionately benefits Western Shore tributaries. That has improved local water quality conditions and helped spur the comeback of underwater grasses in places like the Potomac River.

But the Eastern Shore and Susquehanna River have the greatest influence on the oxygen-starved deep waters of the Upper Bay — the area that has the greatest difficulty in attaining water quality standards. Wastewater is a relatively small contributor to the nutrient pollution coming from those areas.

The Bay TMDL had assigned varying nutrient reductions to different areas to achieve water quality goals in both the Bay and its tidal tributaries. In the past, progress has been evaluated mostly Baywide and state-by-state.

The midpoint evaluation may highlight the need for states to adjust nutrient and sediment control efforts to ensure that pollution reductions come from areas — and from pollution source sectors, such as agriculture and stormwater — where they have been lagging.

“We know that reduced pollutant loads from wastewater treatment plants on the Bay’s Western Shore won’t fully improve water quality conditions in the tidal rivers and creeks along the Eastern Shore,” said Rich Batiuk, associate director for science with the EPA’s Bay Program Office. “And, we know reductions of pollutants from the Eastern Shore have a more positive effect on the main Bay’s water quality conditions compared with the Western Shore. We need to account for that.”

Furthermore, most wastewater treatment plant controls are now in place. Likewise, water quality throughout the region has benefited since the mid-1990s from federal and state air pollution control efforts that have reduced the airborne deposition of nitrogen. But most of those air-quality controls are in place, and future reductions will likely be small. That means more efforts will need to come from sources where progress has been more elusive.

The midpoint assessment will also have to grapple with new science that suggests issues not fully accounted for earlier in the TMDL may pose challenges to cleanup efforts. For instance:

  • Recent studies show Conowingo Dam has largely stopped trapping sediment coming down the Susquehanna River and is now allowing more of it — along with the nutrients attached to the particles of silt — to reach the Bay.
  • Warming water temperatures, new rainfall patterns and rising sea levels are all symptoms of a changing climate that will likely hamper efforts to reach pollution goals.
  • New studies — coupled with water quality monitoring — show that phosphorus-saturated soils in many areas with large livestock populations, especially poultry, are sending more of the nutrient downstream than currently accounted for.

“Folks need to be prepared for change, but not just for change’s sake,” Batiuk said. “New information is going to provide a sharper picture — but a different picture — from what we’ve been working off of.”

The extent, and full impact, of those changes won’t be known until next year. Scientists are still refining estimates, for instance, of how much of a difference things like Conowingo Dam will make. Then, the information has to be fed into newly updated computer models — some still under development — that will recalculate the amount of nutrients coming into the Bay and how that will affect Chesapeake water quality.

A host of other refinements will also influence those results. Updated information on land use, derived from high-resolution photography of the entire 64,000-square-mile watershed, along with zoning and other information provided by many local governments, will provide better information about nutrient runoff. New estimates of the effectiveness of more than 360 runoff control measures, known as best management practices, will allow the computer models to provide a more accurate assessment of nutrient and sediment reduction efforts.

The ultimate clean Bay goal — the maximum amount of nitrogen, phosphorus and sediment that the Bay can receive and still be cleaned up — isn’t expected to change, as those numbers are derived from decades of water quality monitoring and computer models. But factoring in the impacts of Conowingo and phosphorus-saturated soils may mean more action is needed to account for any additional pollution.

“The application of those models will probably adjust the loads among the different source sectors,” said Lee Currey, science services director of the Maryland Department of the Environment and co-chair of the Bay Program Modeling Workgroup. But because there are so many changes, and the new models will not be finalized until next year, he cautioned, “I wouldn’t want to say by how much.”

Currey and others acknowledge that those changes will likely create “winners” and “losers” when nutrient estimates are revised next year. States will use those estimates in 2018 to develop updated cleanup plans that will guide their actions through 2025.

The assessment’s outcome will set the stage for tough policy debates among the EPA and the states. New information could make the cleanup job substantially more difficult — perhaps impossible — for some agricultural areas with phosphorus-saturated soils. Pennsylvania, which is already significantly lagging in its efforts, could face additional burdens related to the Conowingo issue.

Among the questions that could arise: Would other areas, sectors or states be able or willing to take on more of the pollution-reduction burden? Conversely, would states or federal agencies be willing to send more money or resources to problematic areas?

“I think they would be tough conversations to have, but I think we are going to have to have them,” said Beth McGee, senior water quality scientist with the Chesapeake Bay Foundation.

An even more difficult question: If the changes show the cleanup effort is more difficult, will Bay water quality goals actually be attainable?

If not, the water quality standards that define a clean Bay — and determine the needed amount of cleanup efforts — would have to be weakened.

“It’s conceivable that could be the outcome,” Davis-Martin said. “Politically, whether that would happen or not is an issue for the policy folks. But that is certainly one potential outcome.”

McGee said its “too early to throw in the towel” on achieving a clean Bay, and in any event, the environmental group likely “would resist that. It’s possible, she suggested, that the assessment might find the Bay responding better than predicted. “But the notion of an already difficult task being made more difficult,” she added, “is certainly one where we understand the political ramifications.”

Other questions await, as well. One goal of the midpoint assessment is to enlist more local officials in Bay cleanup efforts, by convincing them that the restoration plan is working and fairly apportioned. After the Bay TMDL was issued in 2010, efforts to assign localities cleanup goals met stout pushback in many areas when the Bay watershed model information ran counter to what local officials knew was happening on the ground.

With refined modeling and new land use information — which local governments are being given a chance to review — the Bay Program hopes to gain local officials’  support because much of the remaining Bay pollution reduction efforts must take place at the community level.

State and federal officials want to try again to set local pollution reduction targets in their revised watershed implementation plans. But the extent to which those would be binding, or how localized such targets could be, hasn’t been decided.

And until the local land use and modeling work is finished, it won’t be known how fine-scale model projections can be.

“I think you will have better accuracy of land uses at local scales,” said Dave Montali, of the West Virginia Department of Environmental Protection, and co-chair of the Bay Program Modeling Workgroup. But, he cautioned, “the smaller you go, the less accurate it is going to be.”

Also up for debate is how to factor in land use changes between now and 2025. More development, fewer forests and potentially more farm animals are all changes that could make reaching pollution reduction goals more difficult.

Some advocate projecting future land use to estimate the potential impact on states for planning purposes. Others are resisting planning for changes they say may not occur, or at least as projected.

One thing is certain, though. Even as states prepare for their final push toward the 2025 goal line, the job won’t get any easier. More people, more growth and continuing climate change will pose continued threats to progress being made.

“The idea that we hit 2025 and we’re done, I don’t think it works that way,” Davis-Martin said. “Future generations are going to have to continue to implement practices to maintain progress and offset any changes that occur, additional population growth, etc.”

Key Issues in the Midpoint Assessment

Here’s a look at some of the key issues in the midpoint assessment:

Conowingo Dam: Scientists have long warned that one day the reservoir behind the Conowingo Dam on the Susquehanna River was filling with sediment, and as that happens, more nutrients and sediment pass through the dam and enter the Bay. But when the Chesapeake Bay Total Maximum Daily Load was completed in 2010, it wasn’t recognized that the reservoir had essentially already reached its storage capacity and the flow of nutrients had already increased.

A recent U.S. Army Corps of Engineers report said that offsetting the lost pollution-trapping impact of Conowingo Dam could require 2.4 million additional pounds of nitrogen reductions and 270,000 pounds of additional phosphorus reductions from the Susquehanna River.

Those are reductions that were not factored into the TMDL. Not only are they extra nutrients that have to be controlled, but they are coming from the worst possible place: the Susquehanna. Pound-for-pound, nutrients from the river have a greater impact on dissolved oxygen levels in the deep-water areas of the upper Bay — the area which has the greatest problem meeting water quality standards — than nutrients from other rivers.

Computer modeling shows that if those nutrient reductions don’t come from the Susquehanna, other portions of the Bay watershed would have to cut back by nearly twice as much — 4.4 million pounds of nitrogen and 410,000 pounds of phosphorus — to achieve the same water quality benefit.

Factor in that Pennsylvania, which contributes the lion’s share of the Susquehanna’s nutrients, is already tasked with the greatest reduction burden of any state and is far behind schedule in meeting its goals, and the stage is set for a difficult policy debate, probably next year.

Climate Change: Water in the Bay and its tributary rivers is warming; Chesapeake water levels are rising; and the frequency and severity of storms have been increasing. All of that can affect the amount of nutrients and sediment washing off the land and how they affect water quality.

The interactions are complex: Higher sea levels can draw more ocean water into the Bay and cause more water mixing — which is generally a good thing — but they can also erode shorelines and buffering marshes. Warmer water tends to hold less oxygen than cooler water and threatens the survival of ecologically vital eelgrass in the Lower Bay.

On balance, scientists and officials believe such changes will ultimately make the Bay cleanup more difficult. Key questions: How rapidly will they occur, and will they have an impact by 2025, or sometime later?

At the least, the issue could force a re-examination of some of the best management practices being installed, as well as how to maintain their effectiveness in decades to come. For instance, stormwater and some farm runoff controls may need to be designed to withstand larger, more frequent storms. Building so-called “living shorelines” may become more important in managing erosion and protecting marshes.

Phosphorus: In the past, the Bay Program’s watershed model assumed that the amount of phosphorus that runs off farmland was related to the amount that is applied. But research has shown that in areas where phosphorus levels have built up in soils over many decades, the nutrient continues to leak out even if little or none is spread on fields.

That may help explain why the model shows phosphorus levels going down in some places where water quality monitoring shows worsening trends. A new sub-model is being developed in cooperation with land grant universities and the U.S. Department of Agriculture to better account for the phosphorus buildup in soils. Once completed, it’s likely to discount at least some of the phosphorus reductions previously estimated by the model.

The EPA last year warned states of that likely change, saying the agency “believes that the level of effort to manage phosphorus may increase” and states should “consider additional actions to manage phosphorus” in the future.

Best Management Practices: In the past, the Bay Program only counted a few dozen best management practices, or BMPs, toward meeting nutrient and sediment reduction goals. In the last few years, scores of expert panels have been convened to examine the benefits of new practices — urban tree canopies, oyster aquaculture, street sweeping, manure-to-energy technologies and many more.

But the panels in some cases have recommended changes in the amount of nutrient reductions associated with various BMPs. Further, as they interact with new, fine-scale modeling, the effectiveness of BMPs could be increased or decreased in specific places.

Meanwhile, states have been making efforts to identify conservation practices already adopted by farmers — usually those without cost-share funding from conservation agencies — that haven’t been factored into the cleanup effort yet.

On the other hand, the EPA has also been pressing states to clean up their historic BMP data going back to 1985 and removing from their records those that no longer exist, or those that might have been double-counted.

Also, after 2018, the states must begin periodically inspecting BMPs to ensure that they are maintained and functioning. Those not verified will not be counted toward pollution reduction goals.

New models: The Bay Program partnership relies on a series of computer models that have been developed and refined over three decades to estimate the nutrients and sediment reaching the Bay and how they will impact water quality. There is an air quality model, for instance, that estimates atmospheric deposition on the Bay and its watershed; a watershed model that estimates the movement of nutrients from the land to the Bay; and an estuarine model that simulates water quality in the mainstem of the Chesapeake. In addition, there are a variety of sub-models that cover land uses, the effectiveness of best management practices, underwater grass habitats, oyster filter feeding and more.

The models have undergone significant refinements since they were used to establish TMDL goals in 2010. Changes have focused on the better handling of local movements of nutrients in the watershed — especially phosphorus — and local water quality conditions in shallow parts of the Bay.

The refinements should provide a clearer picture of how nutrients move across the landscape; how that movement may vary regionally; and how the Bay’s water quality is ultimately affected. Because the models are calibrated against decades of historical water-quality monitoring data, their updating should not yield major changes in the overall estimates of nutrients reaching the Bay. It may revise tallies of where nutrients are coming from, though it is too early to say by how much.

Another change: Many of the nutrient reduction actions on the landscape take years before they actually affect the amount reaching the Bay. For the first time, the updated watershed model will be able to give an idea of the time lag— and therefore when the Chesapeake might be cleaned up.

Monitoring: The Bay Program has long been criticized for being overly reliant on computer models as its primary tool for assessing pollution reduction efforts.

Over the last decade and a half, beefed-up monitoring in tributaries has provided better information about trends in nutrient and sediment pollution and their sources. Those data are expected to give the midpoint assessment a better picture of real-world conditions, and what’s driving those trends. Improved monitoring also could play a bigger role in tracking cleanup progress.

EPA officials are already experimenting, for the first time, with translating nutrient reduction goals — now spelled out in pounds removed from wastewater and runoff per year — into predicted loads of nitrogen and phosphorus in some local waterways. Cleanup efforts could then be tracked with real-world water quality monitoring, rather than by relying on simulations of virtual stream conditions generated by computer models.

Land Use: Very little affects nutrient pollution more than land use. For the watershed model, all land in the 64,000-square-mile watershed is given a use, such as impervious surface or pavement, turf grass, pasture, degraded riparian pasture, forest, disturbed forest and so on. Each of these land uses is assigned a different nutrient loading rate by teams of experts based on a variety of factors.

Land use designations in the model have sometimes been highly contentious because in many cases they did not accurately reflect local conditions. For the midpoint assessment, land use information has been overhauled. It’s been revised based on new satellite imagery that provides 1-meter-square detail for the entire watershed, incorporating roads, buildings — even stream forest buffers — that previously went unseen.

In addition, local governments have been invited to provide information on their communities and to review what’s been put together by the Bay Program. So far, local governments representing about 80 percent of the watershed population have provided local land use, land cover, zoning or other information.

Notes on Nutrient and Sediment Trends tables (shown in image box at top of article)

Chesapeake Bay watershed states have made progress, but the region is not on the pace needed to achieve interim 2017 nitrogen or sediment pollution reduction goals, according to figures released in April by the Chesapeake Bay Program.

The figures shown in the tables reflect measured reductions from wastewater treatment plants and estimated reductions from efforts to control pollution from stormwater, farms and other areas.

The phosphorus figures appeared more positive, but Bay program officials cautioned that upcoming revisions to computer models used to estimate the Bay’s nutrient pollution may cast those gains in doubt.

The biggest nitrogen shortfall, by far, is in Pennsylvania, where officials recently announced plans to “reboot” their Bay-related efforts. But New York and Delaware are also off the pace needed to meet 2017 targets.

There are also differences among pollution sources. Nitrogen reductions from wastewater treatment plants are ahead of schedule everywhere except in New York and West Virginia. Watershedwide, plants have slashed nitrogen discharges 75 percent, from 52.2 million pounds in 2009 to 38 million pounds last year — exceeding their 2017 target, and approaching their 2025 goal. Conversely, stormwater controls are not on pace to meet nitrogen goals anywhere. Watershedwide, stormwater nitrogen loads have increased since 2009, the baseline for measuring nutrient reduction progress, from 39.7 million pounds to 40.5 million pounds.

Agriculture, the largest source of nutrients, is not on the trajectory to meet 2017 goals in most states, though the most significant shortfall is in Pennsylvania. Agricultural nitrogen was reduced from 113.8 million pounds in 2009 to 99.2 million pounds in 2015, but needs to reach 88.7 million pounds in 2017 and 71.9 million in 2025.

Editor's note: This article was corrected on May 11 to reflect that West Virginia is on track to meet its 2017 goal.