The amount of nutrient and sediment pollution entering the Chesapeake Bay fell significantly between 2014 and 2015, helping improve water quality in the nation’s largest estuary. Experts attribute this drop in pollution loads to dry weather and below-normal river flow, but note local efforts to reduce pollution also played a role. Indeed, related research shows “best management practices”—including upgrading wastewater treatment plants, lowering vehicle and power plant emissions, and reducing runoff from farmland—have lowered nutrients and sediment in local waterways.
Excess nutrients and sediment are among the leading causes of the Bay’s poor health. Nitrogen and phosphorus can fuel the growth of algae blooms that lead to low-oxygen “dead zones,” while sediment can suffocate shellfish and block sunlight from reaching underwater grasses. By tracking pollution loads into rivers and streams, the Chesapeake Bay Program (CBP) can ensure our partners are on track to meet clean water goals.
According to data from the CBP and the U.S. Geological Survey (USGS), nitrogen, phosphorus and sediment loads to the Bay were below the long-term average in 2015. Between 2014 and 2015, nitrogen loads fell 25 percent, phosphorus loads fell 44 percent and sediment loads fell 59 percent. Below-average loads are considered positive because reductions in nitrogen, phosphorus and sediment pollution can improve water quality.
The most recent assessment of water quality—which examines dissolved oxygen, water clarity and chlorophyll a (a measure of algae growth) in the Bay and its tidal waters—makes these improvements clear: between 2013 and 2015, an estimated 37 percent of the tidal Chesapeake met water quality standards. While this is far below the 100 percent attainment needed for clean water and a stable aquatic habitat, it marks an almost 10 percent improvement from the previous assessment period.
A large portion of pollution loads enters the Bay from the rivers within its watershed. Accordingly, the USGS tracks both annual pollution loads and trends in these loads at monitoring stations along nine of the biggest rivers that feed the Bay. In some cases, long-term pollution trends at these stations reflect efforts to improve water quality. Long-term trends in nitrogen, for example, are improving at six of the nine monitoring stations. Long-term trends in phosphorus and sediment, however, are more variable, and short-term pollution trends show less improvement.
“While the lowered amount of pollution entering the Chesapeake Bay in 2015 is encouraging, the trends of nutrients and sediment over the last decade in the major rivers flowing into the Bay show mixed results,” said U.S. Geological Survey Chesapeake Bay Coordinator Scott Phillips in a media release. “There will need to be improving trends in all of these rivers to support improvement in the Bay’s health.”
Last year’s decline in pollution loads can, in large part, be attributed to favorable weather. While high precipitation can increase river flow and push pollution into the Bay, river flow was below normal in 2015. The long-term decline in pollution loads can also be attributed to on-the-ground pollution-reducing practices, which jurisdictions put in place to meet first the 1983 Chesapeake Bay Agreement, then similar agreements signed in 1987 and 2000, and later the requirements of the Chesapeake Bay Total Maximum Daily Load (Bay TMDL). As of 2015, computer simulations show these practices are in place to achieve 31 percent of the nitrogen reductions, 81 percent of the phosphorus reductions and 48 percent of the sediment reductions necessary to reach our clean water goals.
While improvements in water quality will take time—due in large part to the lag between the implementation of a conservation practice and the visible effect of that practice on a particular waterway—the ecosystem is beginning to respond to protection and restoration efforts. Last year, researchers observed more than 91,000 acres of underwater grasses (also known as submerged aquatic vegetation or SAV) in the Bay, which surpassed the Chesapeake Bay Program’s 2017 restoration target two years ahead of schedule and marked the highest amount ever recorded by the Virginia Institute of Marine Science aerial survey.
“As an SAV biologist, I’m thrilled to see these improving trends in water quality, whether they’re an effect of low flow or our pollution reduction efforts, or both,” said Maryland Department of Natural Resources Biologist and Submerged Aquatic Vegetation Workgroup Chair Brooke Landry. “Better water quality means more SAV, and more SAV means more food and habitat for the fish, invertebrates and waterfowl that depend on it. In 2015, SAV expanded in areas throughout the Bay, and even appeared in places where it's never been recorded before, reaching almost 50 percent of our ultimate restoration goal. This is very exciting and provides the incentive we need to stay on track with our efforts to clean up the Bay. It’s not always easy, but it’s worth it.”
“The ecosystem of the Chesapeake Bay watershed is large and complex and can be affected by a variety of different factors,” said Chesapeake Bay Program Director Nick DiPasquale in a media release. “We are witnessing improvement in a number of our indicators—bay grasses, water clarity and water quality standards attainment, as well as a number of our fisheries such as blue crab population. But we must stay focused and ramp up our pollution reduction efforts if we are to be successful over the long term.”
The early summer dissolved oxygen forecast (called an “anoxia forecast”) is based on nitrogen loads to the Bay during winter and spring, as well as high river flow in May due to heavy rainfall. According to scientists, the Bay’s 2011 low-oxygen area – commonly called the “dead zone” – could be the fourth-largest since 1985.
The annual summer ecological forecast uses data such as nitrogen loads, wind direction and sea level to predict dissolved oxygen levels in the Bay’s mainstem. The forecast is split into early summer (June to mid-July) and late summer (mid-July to September) because scientists have observed a significant change in oxygen levels following early summer wind events.
The forecast is supported through research at the Chesapeake Bay Program, Johns Hopkins University, Old Dominion University, and the University of Maryland Center for Environmental Science Horn Point Lab.
For more information about the dissolved oxygen forecast, visit Chesapeake Eco-Check’s website.
Nutrient pollution in the majority of the Chesapeake Bay region’s freshwater streams and rivers has decreased over the last 25 years, according to data from scientists with the U.S. Geological Survey (USGS) and the Chesapeake Bay Program.
Almost 70 percent of the watershed’s 32 monitoring locations show decreasing nitrogen and phosphorus levels, meaning fewer of these harmful nutrients are entering the Chesapeake’s local waterways. Approximately 40 percent of the sites show decreasing trends for sediment pollution.
Although this data may indicate long-term improvements in the health of the Bay’s streams and rivers, pollution loads to the Bay were higher in 2010 due to more rain, snow and river flow.
“These long-term trends indicate that pollution reduction efforts, such as improved controls at wastewater treatment plants and practices to reduce nutrients and sediment on farms and suburban lands, are improving water quality conditions in many areas,” said USGS scientist Scott Phillips. “However, nutrients, sediment and contaminants will need to be further reduced to achieve a healthier Bay and streams.”
Each day, billions of gallons of fresh water flow through thousands of streams and rivers that eventually empty into the Bay. This fresh water is known as “river flow.” In general, as river flow increases, more nutrient and sediment pollution is carried downstream to the Bay. Pollution levels in rivers vary greatly from year to year because they are influenced by rainfall. Scientists make adjustments to remove the effects of weather variations, allowing consistent measurement of pollution levels over time and better evaluation of long-term changes.
In the 2010 water year (October 2009-September 2010):
The Bay Program’s goal is to have a long-term average of 186 million pounds of nitrogen and 12.5 million pounds of phosphorus entering the Bay from streams and rivers.
In a different, shorter-term study conducted between 2000 and 2008, the health of individual freshwater streams across the watershed showed mixed conditions. Of the 7,886 stream sites sampled, more than half (55 percent) were found to be in very poor or poor condition. The remaining 45 percent were found to be in fair, good or excellent condition.
This study uses data on the tiny, bottom-dwelling creatures that live in freshwater streams and rivers as an indicator of overall stream health. This method provides a uniform evaluation of the health of local waterways across state lines and throughout the entire Bay watershed.
The USGS estimates how much river flow enters the Bay each year, monitors pollution loads in the Bay’s major rivers, and works with the Bay Program to estimate how much pollution reaches the Bay. To learn more about the USGS’s Chesapeake monitoring activities, visit http://chesapeake.usgs.gov.
The Chesapeake Bay has received a C-minus on the University of Maryland Center for Environmental Science’s (UMCES) 2010 Bay Health Report Card. The 2010 grade is a 4 percent decrease from 2009, when the Bay’s health received a C.
Higher rainfall – which led to increased stormwater runoff from the land – drove down scores for water quality and biological heath indicators. Researchers believe that two closely timed, large-scale weather events in winter 2010 played a role in the decrease.
The Bay’s health is affected by many factors, including human activities and natural variations in rainfall, which is the major driver of runoff from farms, cities and suburbs. Even as pollution is reduced, higher rainfall and associated runoff can mask the effects of these improvements.
“One of the main drivers of annual conditions in Chesapeake Bay is river flow related to weather patterns,” said UMCES-EcoCheck scientist Dr. Heath Kelsey. “While efforts to reduce pollution have been stepped up in recent years, nature overwhelmed those measures in 2010 and temporarily set the Bay back a bit.”
The declines are the first observed since 2003 and are on par with conditions observed in 2007. Annual weather-related variability in scores, even as more pollution-reduction measures are put into place, is to be expected in a highly complex ecosystem like the Bay, according to Dr. Kelsey.
Overall, the Lower Bay’s health score stayed relatively steady from 2009, while the Mid- and Upper Bay regions declined slightly. Results were fairly consistent in that declines were seen in most indicators.
The report card, based on data collected by state and federal agencies through the Chesapeake Bay Program, provides an independent analysis of Chesapeake Bay ecosystem health. It is expected that Bay Health Index scores will increase over time, as restoration and pollutant reduction activities are increased.
The report card analysis is conducted through the EcoCheck partnership between UMCES and the NOAA Chesapeake Bay Office. In addition to the Bay-wide reportcard, UMCES works with local watershed organizations to develop river-specific report cards to give residents a creek-by-creek look at their local waters.
For more information about the 2010 Chesapeake Bay Health Report Card, including region-specific data, visit the Chesapeake EcoCheck website.