1. Factors Impacting Bay and Watershed Health
The impact of human activity is overwhelming nature and offsetting cleanup efforts in the Bay and its watershed.
Pollution: The Chesapeake Bay and its tributaries are unhealthy primarily because of pollution from excess nitrogen, phosphorus and sediment entering the water. The main sources of these pollutants are agriculture, urban and suburban runoff, wastewater, and airborne contaminants.
Land Use: One of the greatest challenges to restoration is continued population growth and development, which destroys forests, wetlands and other natural areas.
Natural Factors: Annual rain and snowfall affect how much water flows in rivers. The levels of pollution entering the Bay each year generally correspond with the volume of water that flows from its tributaries.
Other Pressures: There are several other factors that impact the overall health of the ecosystem. These include climate change, invasive species and fisheries harvest.
Additional Information:
Importance: Everything that happens on land has an impact on the water. The man-made pressures on the Chesapeake Bay and its watershed began more than 400 years ago, when the first European colony was founded at Jamestown, Virginia, and Captain John Smith led expeditions around the estuary. During the four centuries that followed, the human population swelled, forests were chopped down, industrial activity ensued, fish and shellfish were harvested, towns and cities were built, and toxic chemicals were released into the environment. These factors disrupted the natural functioning of the entire ecosystem and led to a tremendous decline in the Bay’s health. Today, human activity continues to drive the primary sources of pollution, which are agriculture, urban and suburban lands, wastewater, and air pollution.
Goal: The factors impacting Bay and watershed health are tracked with 12 “reporting-level” indicators grouped in four priority areas that represent major stressors to the Bay ecosystem. The indicators are not related to goals at this time.
In Factors Impacting Bay and Watershed Health, the most current monitoring data available are used to provide an assessment of various factors impacting the health of the Bay and its watershed.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

2. Pollutants Pollutants
Status: Annual rain and snowfall affect how much water flows in rivers. The levels of pollution entering the Bay each year generally correspond with the volume of water that flows from its tributaries.
Nitrogen: Preliminary estimates indicate that 291 million pounds of nitrogen reached the Bay during This is 13 million pounds less than 2007 and 54 million pounds less than the 345 million pound average load from
Phosphorus: Preliminary estimates indicate that 13.8 million pounds of phosphorus reached the Bay during This is the same as 2007 and 7.5 million pounds less than the 21.3 million pound average load from
Sediment: Preliminary estimates indicate that 3.3 million tons of sediment reached the Bay during This is 700,000 tons more than 2007 and 800,000 tons less than the 4.1 million ton average load from The sediment load estimates do not account for sediment from the coastal plain areas of the watershed. Scientists are currently developing methods to quantify the total loads of sediment to the Bay.
Additional Information:
Importance: The Chesapeake Bay and its tributaries are unhealthy primarily because of pollution from excess nitrogen, phosphorus and sediment entering the water. The main sources of these pollutants are agriculture, urban and suburban runoff, wastewater, and airborne contaminants.
Agriculture: Agriculture covers about 25 percent of the watershed, representing the largest intensively managed land use. There are an estimated 87,000 farms covering about 8.5 million acres. Agriculture is the number one source of pollution to the Bay. Improperly applied fertilizers and pesticides flow into creeks, streams and rivers, carrying excess nitrogen, phosphorus and chemicals into the Chesapeake Bay. Tilling cropland and irrigating fields can cause major erosion. Additionally, the nutrients and bacteria found in animal manure can seep into groundwater and runoff into waterways.
Urban and Suburban Lands: Human development, ranging from small subdivisions to large cities, is a major source of pollution for the Chesapeake. In fact, because of the region’s continued population growth and related construction, runoff from urban and suburban lands is the only source of pollution that is increasing. These areas are covered by impervious surfaces – such as roads, rooftops and parking lots – that are hard and don’t let water penetrate. As a result, water runs off into waterways instead of filtering into the ground. This runoff carries pollutants including lawn fertilizer, pet waste, chemicals and trash. Septic systems release pollution that eventually ends up in the water. Developed areas also split up forests, decreasing their filtering capacity.
Wastewater: There is a tremendous volume of sewage that must be processed in the watershed. The technology used by the 483 major municipal and industrial wastewater treatment plants has not removed enough pollution, particularly nitrogen and phosphorus. Upgrading these facilities so they can remove more pollution from the water is extremely expensive and takes time. While there has been significant progress in improving treatment at many wastewater plants, numerous facilities still use old technology. Also, population growth is increasing the need for wastewater treatment, causing some facilities to be expanded..
Air Pollution: When pollution is released into the air, it eventually falls onto land and water. Even larger than the Chesapeake Bay’s watershed is its airshed, the area from which pollution in the atmosphere settles into the region. This airshed is about 570,000 square miles, or seven times the size of the watershed. Nitrogen and chemical contaminants – such as mercury and PCBs – from air pollution contribute to poor water quality in the region, and about half of these pollutants come from outside the watershed. Air pollution is generated by a variety of sources, including power plants, industrial facilities, farming operations, and automobiles and other gas-powered vehicles.
Goal: Scientists have estimated the threshold levels of nitrogen, phosphorus and sediment that should not be exceeded for a healthy Bay. However, the levels entering the Bay each year can not be directly related to the thresholds. Work is ongoing to develop new flow-adjusted total nutrient load indicators that can be compared to the thresholds and that can better track the progress of nutrient management programs within the watershed.
The Bay's watershed covers an enormous 64,000-square-mile area that includes parts of six states – Delaware, Maryland, New York, Pennsylvania, Virginia and West Virginia – and all of the District of Columbia. Billions of gallons of water flow each day through thousands of streams and rivers that eventually empty into the Bay. The Bay must process runoff from a large amount of land with a relatively small body of water.
Runoff from winter and spring rains deliver loads of sediment and nutrient pollutants to the Bay that drive summer water quality conditions in the Bay. Past observations reveal that summer weather conditions also contribute to summer water quality when intense storms increase erosion, which contributes to poor water clarity and adds to the existing nutrient load in the Bay.
Not all rain water “runs off” the land. Some water seeps into the soil, carrying nutrients into groundwater. The travel time of nutrients through the watershed ranges from weeks to centuries. This can result in a “lag time” between implementing management actions and improvements in water quality.
Sediment continues to have an adverse impact on water clarity and underwater grasses in the Bay and stream quality in the watershed.
Synthetic organic pesticides and their degradation products have been widely detected at low levels in the watershed, including emerging contaminants such as pharmaceuticals and hormones.
Fish (principally male bass) in the Potomac watershed have testicular oocytes - female eggs growing in their testes - a form of intersex. Reproductive abnormalities in fish have been strongly linked with a variety of contaminants that affect the endocrine systems of fish.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

3. Nitrogen Loads and River Flow to the Bay
Nitrogen Loads and River Flow to Chesapeake Bay
Millions of Pounds
of Nitrogen
Billions of
Gallons of Flow
River Flow
Nitrogen Loads and River Flow to the Bay
Status:
Nitrogen: Preliminary estimates indicate that 291 million pounds of nitrogen reached the Bay during This is 13 million pounds less than 2007 and 54 million pounds less than the 345 million pound average load from
River Flow: Total river flow to the Bay during the 2008 water year (October 2007-September 2008) was 37.5 billion gallons per day (BGD). This is 3.5 BGD less than 2007 and 10 BGD less than the 47.2 BGD average flow from
Additional Information:
Importance:
Each day, billions of gallons of fresh water flow through thousands of streams and rivers that eventually empty into the Chesapeake Bay. That water also carries polluted runoff from throughout the watershed. The amount of water flowing into the Bay from its tributaries has a direct impact on how much pollution is in the estuary – generally as river flow increases it brings more nitrogen and phosphorus to the Bay. The volume of river water flowing into the Bay also affects the saltiness (salinity) of Bay waters. In addition, fast-moving and turbulent river flow mixes in oxygen from the air, which is beneficial for aquatic life. Years with low or high amounts of precipitation can result in changes to pollution levels in the Bay, but not mean the health of the watershed is improving or declining.
Runoff from winter and spring rains deliver loads of sediment and nutrient pollutants to the Bay that drive summer water quality conditions in the Bay. Past observations reveal that summer weather conditions also contribute to summer water quality when intense storms increase erosion, which contributes to poor water clarity and adds to the existing nutrient load in the Bay.
Not all rain water “runs off” the land. Some water seeps into the soil, carrying nutrients into groundwater. The travel time of nutrients through the watershed ranges from weeks to centuries. This can result in a “lag time” between implementing management actions and improvements in water quality.
Goal: Scientists have estimated the threshold level of nitrogen that should not be exceeded for a healthy Bay. However, the nitrogen loads entering the Bay each year can not be directly related to the threshold. Work is ongoing to develop a new flow-adjusted total nitrogen load indicator that can be compared to the threshold and that can better track the progress of nutrient management programs within the watershed.
Trends:
Nitrogen:
What is the long-term trend? (since start of data collection) 1990 was the first year where all necessary loads data were available. Rigorous statistical analyses to determine trends in loads have not been developed at this time. The amount of nutrients delivered to the Bay from the watershed changes dramatically from year-to-year complicating efforts to determine trends through time. Between 1990 and 2008, nitrogen loads averaged 345 million pounds per year and ranged from 174 to 514 million pounds per year. Nitrogen loads decreased from 341 to 291 million pounds per year,
What is the short-term trend? (10 year trend) The last 10 years have highly variable nitrogen loads with being very low load years followed by two much higher load years. Between , nitrogen loads increased from 177 to 291 million pounds per year.
Change from previous year: : Nitrogen loads decreased from 304 to 291 million pounds per year.
River Flow:
What is the long-term trend? (since start of data collection) Between 1938 and 2008, river flow to the Bay has averaged 47.2 BGD and has ranged from 21.9 to 78.2 BGD. The Climate Change and the Chesapeake Bay State-of-the-Science Review and Recommendations: A Report from the Chesapeake Bay Program Science and Technical Advisory Committee (STAC) highlighted an examination of the 1957 to 2000 record of annual streamflow into the Chesapeake and found substantial interannual variability as well as decadal variability characterized by dry conditions during the 1960s, wet conditions during the 1970s, and relatively normal conditions since then. There was no obvious long-term trend.
What is the short-term trend? (10 year trend) The last 10 years have highly variable flow. Between , river flow increased from 21.9 to 37.5 BGD.
Change from previous year: : river flow decreased from 41 to 37.5 BGD.
To calculate the loads of nitrogen flowing to the Bay, scientists use a combination of water samples and computer modeling. Whenever possible and practical, samples from rivers and wastewater pipes are used to measure pollution levels. Using this technique, pollution loads can be calculated for almost 80 percent of the watershed. For the remaining area, computer modeling is used to calculate pollution loads.
Average Load
Data and Methods: data are provisional.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

4. Phosphorus Loads and River Flow to the Bay
Phosphorus Loads and River Flow to Chesapeake Bay
Millions of Pounds
of Phosphorus
Billions of
Gallons of Flow
River Flow
Phosphorus Loads and River Flow to the Bay
Status:
Phosphorus: Preliminary estimates indicate that 13.8 million pounds of phosphorus reached the Bay during This is the same as 2007 and 7.5 million pounds less than the 21.3 million pound average load from
River Flow: Total river flow to the Bay during the 2008 water year (October 2007-September 2008) was 37.5 billion gallons per day (BGD). This is 3.5 BGD less than 2007 and 10 BGD less than the 47.2 BGD average flow from
Additional Information:
Importance:
Each day, billions of gallons of fresh water flow through thousands of streams and rivers that eventually empty into the Chesapeake Bay. That water also carries polluted runoff from throughout the watershed. The amount of water flowing into the Bay from its tributaries has a direct impact on how much pollution is in the estuary – generally as river flow increases it brings more nitrogen and phosphorus to the Bay. The volume of river water flowing into the Bay also affects the saltiness (salinity) of Bay waters. In addition, fast-moving and turbulent river flow mixes in oxygen from the air, which is beneficial for aquatic life. Years with low or high amounts of precipitation can result in changes to pollution levels in the Bay, but not mean the health of the watershed is improving or declining.
Runoff from winter and spring rains deliver loads of sediment and nutrient pollutants to the Bay that drive summer water quality conditions in the Bay. Past observations reveal that summer weather conditions also contribute to summer water quality when intense storms increase erosion, which contributes to poor water clarity and adds to the existing nutrient load in the Bay.
Not all rain water “runs off” the land. Some water seeps into the soil, carrying nutrients into groundwater. The travel time of nutrients through the watershed ranges from weeks to centuries. This can result in a “lag time” between implementing management actions and improvements in water quality.
Goal: Scientists have estimated the threshold level of phosphorus that should not be exceeded for a healthy Bay. However, the phosphorus loads entering the Bay each year can not be directly related to the threshold. Work is ongoing to develop a new flow-adjusted total phosphorus load indicator that can be compared to the threshold and that can better track the progress of nutrient management programs within the watershed.
Trends:
Phosphorus:
What is the long-term trend? (since start of data collection) 1990 was the first year where all necessary loads data were available. Rigorous statistical analyses to determine trends in loads have not been developed at this time. The amount of nutrients delivered to the Bay from the watershed changes dramatically from year-to-year complicating efforts to determine trends through time. Between 1990 and 2008, phosphorus loads averaged 21.3 million pounds per year and ranged from 7.1 to 46.4 million pounds per year. Phosphorus loads decreased from 17.2 to 13.8 million pounds per year,
What is the short-term trend? (10 year trend) The last 10 years have highly variable phosphorus loads with being very low load years followed by two much higher load years. Between , phosphorus loads increased from 7.1 to 13.8 million pounds per year.
Change from previous year: : Between 2007 and 2008 there was no significant change in phosphorus loads (from 14.1 to 13.8 million pounds per year).
River Flow:
What is the long-term trend? (since start of data collection) Between 1938 and 2008, river flow to the Bay has averaged 47.2 BGD and has ranged from 21.9 to 78.2 BGD. The Climate Change and the Chesapeake Bay State-of-the-Science Review and Recommendations: A Report from the Chesapeake Bay Program Science and Technical Advisory Committee (STAC) highlighted an examination of the 1957 to 2000 record of annual streamflow into the Chesapeake and found substantial interannual variability as well as decadal variability characterized by dry conditions during the 1960s, wet conditions during the 1970s, and relatively normal conditions since then. There was no obvious long-term trend.
What is the short-term trend? (10 year trend) The last 10 years have highly variable flow. Between , river flow increased from 21.9 to 37.5 BGD.
Change from previous year: : river flow decreased from 41 to 37.5 BGD.
To calculate the loads of phosphorus flowing to the Bay, scientists use a combination of water samples and computer modeling. Whenever possible and practical, samples from rivers and wastewater pipes are used to measure pollution levels. Using this technique, pollution loads can be calculated for almost 80 percent of the watershed. For the remaining area, computer modeling is used to calculate pollution loads.
Average Load
Data and Methods: data are provisional.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

5. Sediment Loads and River Flow to the Bay
Preliminary estimates indicate that 3.3 million tons of sediment reached the Bay during This is 700,000 tons more than 2007 and 800,000 tons less than the 4.1 million ton average load from
The sediment load estimates do not account for sediment from the coastal plain areas of the watershed.
Scientists are currently developing methods to quantify the total loads of sediment to the Bay.
Sediment Loads and River Flow to the Bay
Status:
Sediment: Preliminary estimates indicate that 3.3 million tons of sediment reached the Bay during This is 700,000 tons more than 2007 and 800,000 tons less than the 4.1 million ton average load from The sediment load estimates do not account for sediment from the coastal plain areas of the watershed. Scientists are currently developing methods to quantify the total loads of sediment to the Bay.
River Flow: Total river flow to the Bay during the 2008 water year (October 2007-September 2008) was 37.5 billion gallons per day (BGD). This is 3.5 BGD less than 2007 and 10 BGD less than the 47.2 BGD average flow from
Additional Information:
Importance:
Each day, billions of gallons of fresh water flow through thousands of streams and rivers that eventually empty into the Chesapeake Bay. That water also carries polluted runoff from throughout the watershed. The amount of water flowing into the Bay from its tributaries has a direct impact on how much pollution is in the estuary – generally as river flow increases it brings more sediment to the Bay. The volume of river water flowing into the Bay also affects the saltiness (salinity) of Bay waters. In addition, fast-moving and turbulent river flow mixes in oxygen from the air, which is beneficial for aquatic life. Years with low or high amounts of precipitation can result in changes to pollution levels in the Bay, but not mean the health of the watershed is improving or declining.
Runoff from winter and spring rains deliver loads of sediment and nutrient pollutants to the Bay that drive summer water quality conditions in the Bay. Past observations reveal that summer weather conditions also contribute to summer water quality when intense storms increase erosion, which contributes to poor water clarity and adds to the existing nutrient load in the Bay.
Goal: Scientists have estimated the threshold level of sediment that should not be exceeded for a healthy Bay. However, the sediment loads entering the Bay each year can not be directly related to the threshold.
Trends:
Sediment:
What is the long-term trend? (since start of data collection) 1990 was the first year where all necessary loads data were available. Rigorous statistical analyses to determine trends in loads have not been developed at this time. The amount of sediment delivered to the Bay from the watershed changes dramatically from year-to-year complicating efforts to determine trends through time. Between 1990 and 2008, sediment loads averaged 4.1 million tons per year and ranged from 0.6 to 12.2 million tons per year. Sediment loads increased from 2 to 3.3 million tons per year, Note: The sediment load estimates do not account for sediment from the coastal plain areas of the watershed. Scientists are currently developing methods to quantify the total loads of sediment to the Bay.
What is the short-term trend? (10 year trend) The last 10 years have highly variable sediment loads with being very low load years followed by two much higher load years. Between , sediment loads increased from 0.7 to 3.3 million tons per year. Note: The sediment load estimates do not account for sediment from the coastal plain areas of the watershed. Scientists are currently developing methods to quantify the total loads of sediment to the Bay.
Change from previous year: : sediment loads increased from 2.6 to 3.3 million tons per year. Note: The sediment load estimates do not account for sediment from the coastal plain areas of the watershed. Scientists are currently developing methods to quantify the total loads of sediment to the Bay.
River Flow:
What is the long-term trend? (since start of data collection) Between 1938 and 2008, river flow to the Bay has averaged 47.2 BGD and has ranged from 21.9 to 78.2 BGD. The Climate Change and the Chesapeake Bay State-of-the-Science Review and Recommendations: A Report from the Chesapeake Bay Program Science and Technical Advisory Committee (STAC) highlighted an examination of the 1957 to 2000 record of annual streamflow into the Chesapeake and found substantial interannual variability as well as decadal variability characterized by dry conditions during the 1960s, wet conditions during the 1970s, and relatively normal conditions since then. There was no obvious long-term trend.
What is the short-term trend? (10 year trend) The last 10 years have highly variable flow. Between , river flow increased from 21.9 to 37.5 BGD.
Change from previous year: : river flow decreased from 41 to 37.5 BGD.
To calculate the loads of sediment flowing to the Bay, scientists take water samples near the head of tide (fall line) in the Bay's major rivers. The volume of water flowing past the monitoring gauges – or river flow – and sediment concentrations are measured. The sediment load estimates do not account for sediment from the coastal plain areas of the watershed (areas below the fall line). Scientists are currently developing methods to quantify the total loads of sediment to the Bay.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

6. Chemical Contaminant Loads to the Bay
Synthetic organic pesticides and their degradation products have been widely detected at low levels in the watershed, including emerging contaminants such as pharmaceuticals and hormones.
Fish (principally male bass) in the Potomac watershed have testicular oocytes - female eggs growing in their testes - a form of intersex. Reproductive abnormalities in fish have been strongly linked with a variety of contaminants that affect the endocrine systems of fish.
Scientists are currently developing methods to quantify chemical contaminant loads to the Bay.
Status:
Synthetic organic pesticides and their degradation products have been widely detected at low levels in the watershed, including emerging contaminants such as pharmaceuticals and hormones.
Fish (principally male bass) in the Potomac watershed have testicular oocytes - female eggs growing in their testes - a form of intersex. Reproductive abnormalities in fish have been strongly linked with a variety of contaminants that affect the endocrine systems of fish.
Scientists are currently developing methods to quantify chemical contaminant loads to the Bay.
Additional Information:
Annual Chesapeake Bay water quality conditions are largely determined by a combination of the amount of pollution deposited on the land or discharged in wastewater and the amount of water flowing into the Bay. As the volume of water flowing into the Bay – or river flow – increases, its potential to carry increased pollutants increases as well.
The Chesapeake Bay Program (CBP) has set as its ultimate goal a Chesapeake Bay free of toxic impacts. This goal will be achieved by reducing or eliminating the input of chemical contaminants to levels that result in no toxic or bioaccumulative impact on the living resources that inhabit the Bay or on human health.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

7. Land Use
Land Use
Status: The Bay watershed is home to almost 17 million people. About 150,000 people move to the area each year. About 58 percent of the watershed is forest. The rest of the land has been developed for other uses, such as agriculture and urban and suburban lands.
Additional Information:
Importance: One of the greatest challenges to restoration is continued population growth and development, which destroys forests, wetlands and other natural areas. The impact of human activity is overwhelming nature and offsetting cleanup efforts.
Goal: The indicators are not related to goals at this time.
The Bay watershed spreads over 64,000 square miles, creating some of the most special land and water areas in our country. The Chesapeake's future depends on the choices made every day by the millions of people who live within the Bay watershed.
What each of us does on the land—including the use of vehicles, fertilizers, pesticides, electricity and water—affects our streams, rivers and ultimately the Bay.
Population growth and agricultural lands have contributed to an overabundance of nutrients, sediment and contaminants entering the Bay, and loss of habitats that can retain these pollutants.
Impervious surfaces increased 41 percent during the 1990s compared to an 8-percent increase in population. The rate of increase of impervious surface implies there will be more rapid delivery of nutrients to streams and an increase in sediment erosion.
Experts predict that the population will increase to about 20 million by 2030.
One hundred acres of forest are lost each day in the watershed. As forests and wetlands are destroyed to make room for roads and buildings, their ability to hold back pollutants and the important habitat they offer are lost as well.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

8. Bay Watershed Population and Impervious Surface
Millions of Acres of Impervious Surface
Millions of People
Population
Impervious Surface
Projection
Bay Watershed Population and Impervious Surface
Status: 16,797,132 people live in the watershed.
Additional Information:
Importance:
How humans use the land has the greatest impact on the Chesapeake Bay and local waterways. Natural areas like forests and wetlands have a positive effect on water quality, while areas developed for farming or cities generally have a negative impact. The decline of the Chesapeake Bay is directly linked to the rise in population of the watershed – since 1950 the number of residents has doubled. Projections through 2030 show continued population growth, loss of natural areas and increases in urban development, which are all challenges to protecting and restoring the Chesapeake.
Even more influential than population growth is the corresponding development. People are moving into sprawling suburbs and living in bigger houses on larger lots, causing forests, farms and other valuable lands to be transformed into subdivisions, shopping centers and parking lots. This land conversion severely impacts the health of streams, rivers and the Bay. Impervious surfaces such as roads and rooftops do not allow water to filter into the ground. Instead rainfall runs off, picking up pollution and quickly carrying it into waterways. From 1990 to 2000, impervious surfaces increased by 41 percent – a rate five times greater than the 8 percent rate of population growth during that time.
Goal: The indicator is not related to a goal at this time.
Trends:
What is the long-term trend? (since start of data collection) Population increased from 8,385,982 to 16,797,132,
What is the short-term trend? (10 year trend) 10-year trend not available since most recent annual data points are 2000 through Population increased from 15,700,408 to 16,797,132,
Change from previous year: : Population increased from 16,684,893 to 16,797,132.
Experts predict that population will increase to nearly 20 million by 2030.
In the future, the CBPO will be tracking change in developed area rather than change in impervious surfaces. Impervious surfaces are a sub-category of developed lands.
Impervious surface is defined as a surface or area that is hardened and does not allow water to pass through. Roads, rooftops, driveways, sidewalks, pools, patios and parking lots are all impervious surfaces.
The land area of the Chesapeake Bay watershed is 64,000 square miles or ~40.9 million acres. The total acres of imperviousness in the watershed in 1990 was 602,766 acres and in 2000 it increased to 848,727 acres – an increase of 245,961 acres or 40.8%.
While the overall population of the Bay watershed continues to grow, population changes vary from state to state and region to region. Some areas are gaining population at a high rate, while populations in other areas are leveling out or declining.
Data and Methods:
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

9. Bay Watershed Forest Cover
Percent Forest Cover
Bay Watershed Forest Cover
Status: In the 1600s, forests covered 95 percent of the watershed. Now only 58 percent of the watershed is forested, and development is reducing forests at the rate of 100 acres per day. Also because of development, forested areas are being split into smaller parcels, which reduce their ability to improve water quality and provide wildlife habitat.
Additional Information:
Importance: Forests protect and filter drinking water for 75 percent of the Bay watershed’s residents and provide valuable ecological services and economic benefits including carbon sequestration, flood control, wildlife habitat and forest products. Forests are the most beneficial use of land for Bay water quality. They capture, filter and retain water, thereby reducing pollution and improving water quality. Forests also absorb air pollution and retain up to 85 percent of the nitrogen from sources such as automobiles and power plants. Forested areas reduce erosion, control flooding and provide habitat for wildlife.
Goals:
In recognition of the unique and irreplaceable functions of urban and rural forests to the health, well-being and livelihood of the citizens of the watershed, Bay Program partners agreed to look beyond traditional programs and act now to accelerate the conservation and stewardship of our most valuable forests. In the 2006 Forest Conservation Directive, they committed to developing a collective goal to be adopted by the Chesapeake Executive Council in 2007, for conserving those forest lands in the Bay watershed where conservation to protect water quality is most needed.
At its annual meeting in December 2007, the Bay Program partners signed the Forestry Conservation Initiative, committing the Bay states to permanently conserve an additional 695,000 acres of forested land throughout the watershed by 2020.
There are four overarching goals to the Forestry Conservation Initiative:
By 2020, permanently protect an additional 695,000 acres of forest from conversion to other land uses such as development, targeting forests in areas of highest water quality value. As part of this goal, 266,400 acres of forest land under threat of conversion will be protected by 2012.
By 2020, accelerate reforestation and conservation in:
Urban and suburban areas by increasing the number of communities with commitments to tree canopy expansion goals to 120.
Riparian forest buffers by reaching a restoration rate of 900 miles per year until 70 percent of all stream miles in the watershed are buffered over the long term.
By 2010, work with local governments, legislative delegations, land trusts or other stakeholders to create or augment dedicated sources of local funding, such as through ballot initiatives, for the conservation of forests important to water quality. Where possible, the states will support these through incentive programs (e.g., matching grants).
By 2009, establish and implement a mechanism to track and assess forest land cover change at the county and township scale every five years, and to deliver this capacity to local governments, watershed groups and other partners.
In addition, each state and the federal agencies will implement strategies and actions to:
Establish policies that discourage conversion of valuable forestlands.
Collaborate with local governments to incorporate forest conservation into their land use plans and ordinances.
Establish strong economic incentives for working forest landowners.
Use forests as green infrastructure to reduce nutrient loads from development.
Use federal Farm Bill programs to support working forest conservation.
Trends:
What is the long-term trend? (since start of data collection) Decreased from 95% to 58% forest cover,
What is the short-term trend? (10 year trend) 10-year trend not available since most recent data points are 1990 and Decreased from 59% to 58% forest cover,
Change from previous year: Not available.
More than 750,000 acres—equivalent to 20 Washington, DCs— have been developed since the early 1980s. If current trends continue, an additional 9.5 million acres of Chesapeake forests will be threatened by conversion to residential development by 2030.
As forests and wetlands are destroyed to make room for roads and buildings, their ability to hold back pollutants and the important habitat they offer are lost as well.
Retaining and expanding forests in the Chesapeake Bay watershed is critical to our success in restoring the Chesapeake Bay. Forests are the most beneficial land use for protecting water quality, due to their ability to capture, filter and retain water, as well as absorb pollution from the air. In fact, our watershed forests are excellent assimilators of air pollution, retaining up to 85 percent of the nitrogen they receive from air emission sources such as motor vehicles and electric utilities. Conversely, a reduction in forest area leads to a disproportionate increase in nitrogen loads to our waterways.
The State of Chesapeake Forests report estimates that over 35 percent of the region’s private forests are vulnerable to development and, of those vulnerable forestlands, 3.5 million acres are among the most valuable for protecting water quality. Further, the report recognizes that more proactive stewardship of public and private forestlands is needed in order to sustain the many benefits they provide to the Bay watershed and its residents.
In Chesapeake 2000, the Bay Program partners committed to “Permanently preserve from development 20 percent of the land area in the watershed by 2010” and “Conserve existing forests along all streams and shorelines.” They further committed to expand urban tree canopy and link forests with stormwater management.
Land conservation efforts to date, which have been extremely successful, have not significantly targeted forest lands. Tools, such as the Resource Lands Assessment called for in Chesapeake 2000, that can identify priority forest lands with the greatest impact on watershed function and water quality.
The graph above shows the percentage of forest cover in the basin during particular times since Since 1650 nearly all of the forested land in the basin has been cut at one time or another. Isolated remnants of 'virgin' forest (never cut) exist in very small quantities. From 1750 to 1890 most land in the watershed was cleared for farming, timber and fuel. In the last 20 years, most deforestation has been due to urban sprawl and some agricultural conversion.
Some areas facing rapid growth or supporting intense agricultural uses have lost 80 percent of their historic forest cover. Areas closest to the Bay have seen the most rapid forest loss. Recent findings suggest that fragmentation, created by urban sprawl and agriculture, can affect stream health, habitat quality and economic viability of forest patches.
Forest quality may be as important to Bay health as the quantity of acres. Several factors are particularly key:
Proximity to water;
Species diversity;
Ecosystem resilience;
Habitat fragmentation; and
Economic viability.
Forests contribute to the Bay's health by:
Filtering nutrients and sediment;
Capturing rainfall and regulating streamflow;
Moderating stream and air temperatures;
Stabilizing soils to prevent erosion; and
Creating and maintaining fish and wildlife habitat; and preserving biodiversity.
Forests growing along streams and waterways, also known as 'riparian forests', play an important role in preventing pollutants and sediment from pouring into local waterways and the Bay. They also provide food, shelter, nesting sites and safe migration paths for Bay area wildlife.
Urban forests also are important in developed parts of the watershed. Trees in our cities and suburbs contribute to improved water quality, air quality and wildlife habitat.
Data and Methods:
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

10. Natural Factors
Natural Factors
Status: Total river flow to the Bay during the 2008 water year (October 2007-September 2008) was 37.5 billion gallons per day (BGD). This is 3.5 BGD less than 2007 and 10 BGD less than the 47.2 BGD average flow from
Additional Information:
Importance: Natural factors, such as temperatures and wind, as well as precipitation which affects the volume of water flowing into the Bay, have a great impact on water quality, habitat and fish and shellfish populations. Annual rain and snowfall affect how much water flows in rivers. The levels of pollution entering the Bay each year generally correspond with the volume of water that flows from its tributaries.
Goal: The indicators are not related to goals at this time.
Precipitation and River Flow:
Rainfall and snowfall affect the volume of water flowing into the Bay – or river flow – from its many freshwater streams and rivers.
Each day, billions of gallons of fresh water flow through thousands of streams and rivers that eventually empty into the Chesapeake Bay. That water also carries polluted runoff from throughout the watershed. The amount of water flowing into the Bay from its tributaries has a direct impact on how much pollution is in the estuary – generally as river flow increases it brings more pollution to the Bay.
The volume of river water flowing into the Bay also affects the saltiness (salinity) of Bay waters.
In addition, fast-moving and turbulent river flow mixes in oxygen from the air, which is beneficial for aquatic life.
Years with low or high amounts of precipitation can result in changes to pollution levels in the Bay, but not mean the health of the watershed is improving or declining.
Runoff from winter and spring rains deliver loads of sediment and nutrient pollutants to the Bay that drive summer water quality conditions in the Bay. Past observations reveal that summer weather conditions also contribute to summer water quality when intense storms increase erosion, which contributes to poor water clarity and adds to the existing nutrient load in the Bay.
Not all rain water “runs off” the land. Some water seeps into the soil, carrying nutrients into groundwater. The travel time of nutrients through the watershed ranges from weeks to centuries. This can result in a “lag time” between implementing management actions and improvements in water quality.
Temperature:
Changes in water temperature influence when plants and animals feed, reproduce, move locally or migrate. Temperature plays a critical role in determining the amount of dissolved oxygen in the Bay’s waters. High water temperatures may also affect underwater grass beds.
Temperature dramatically changes the rate of chemical and biological reactions within the water. Because the Bay is so shallow, its capacity to store heat over time is relatively small. As a result, water temperature fluctuates throughout the year, ranging from 34 to 84 degrees Fahrenheit. These changes in water temperature influence when plants and animals feed, reproduce, move locally or migrate.
The temperature profile of the Bay is fairly predictable. During spring and summer, surface and shallow waters are warmer than deeper waters, creating two distinct temperature layers. The turbulence of the water can help to break down this layering. In autumn, fresher surface waters cool faster than deeper waters and sink. Vertical mixing of the two water layers occurs rapidly, usually overnight. This mixing moves nutrients up from the bottom, making them available to phytoplankton and other organisms inhabiting upper water levels. This turnover also distributes much-needed dissolved oxygen to deeper waters. During the winter, water temperature is relatively constant from surface to bottom.
Temperature plays a critical role in determining the amount of dissolved oxygen in the Bay’s waters. The colder the water, the more oxygen it can hold. Therefore, the waters of the Chesapeake Bay have a greater capacity to hold dissolved oxygen during the cold winter months than they do during the summer months.
High water temperatures may affect underwater grass beds. Last year, warmer than average water temperatures may have caused the large scale loss of eelgrass in Tangier Sound. And while high temperatures can negatively affect SAV, they aid in the growth of something not so desirable: algae. These tiny plants flourish in the hot summer sun, soaking up rays and nutrients, but often multiplying to unhealthy proportions. These harmful algae blooms can block out sunlight needed by SAV, or produce toxins that kill fish and sicken humans.
Wind:
Wind also plays an important role by mixing the surface of the water and increasing oxygen levels in the Bay.
Just as circulation moves much-needed blood throughout the human body, circulation of water transports plankton, fish eggs, shellfish larvae, sediments, dissolved oxygen, minerals and nutrients throughout the Bay. Circulation is driven primarily by the movements of freshwater from the north and saltwater from the south. Circulation causes nutrients and sediments to be mixed and resuspended. This mixing creates a zone of maximum turbidity that, due to the amount of available nutrients, is often used as a nursery area for fish and other organisms.
Weather can disrupt or reinforce this two-layered circulation pattern. Wind plays a role in the mixing of the Bay's waters. Wind also can raise or lower the level of surface waters and occasionally reverse the direction of flow. Strong northwest winds, associated with high-pressure areas, push water away from the Atlantic Coast, creating exceptionally low tides. Strong northeast winds, associated with low-pressure areas, produce exceptionally high tides.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

11. River Flow into Chesapeake Bay
Water Year Mean River Flow (billions of gallons per day)
Wet Years
River Flow into Chesapeake Bay
Status: Total river flow to the Bay during the 2008 water year (October 2007-September 2008) was 37.5 billion gallons per day (BGD). This is 3.5 BGD less than 2007 and 10 BGD less than the 47.2 BGD average flow from
Additional Information:
Importance:
Annual rain and snowfall affect the volume of water flowing into the Bay – or river flow – from its many freshwater streams and rivers.
Each day, billions of gallons of fresh water flow through thousands of streams and rivers that eventually empty into the Chesapeake Bay. That water also carries polluted runoff from throughout the watershed. The amount of water flowing into the Bay from its tributaries has a direct impact on how much pollution is in the estuary – generally as river flow increases it brings more nitrogen and phosphorus to the Bay.
The volume of river water flowing into the Bay also affects the saltiness (salinity) of Bay waters.
In addition, fast-moving and turbulent river flow mixes in oxygen from the air, which is beneficial for aquatic life.
Years with low or high amounts of precipitation can result in changes to pollution levels in the Bay, but not mean the health of the watershed is improving or declining.
Runoff from winter and spring rains deliver loads of sediment and nutrient pollutants to the Bay that drive summer water quality conditions in the Bay. Past observations reveal that summer weather conditions also contribute to summer water quality when intense storms increase erosion, which contributes to poor water clarity and adds to the existing nutrient load in the Bay.
Not all rain water “runs off” the land. Some water seeps into the soil, carrying nutrients into groundwater. The travel time of nutrients through the watershed ranges from weeks to centuries. This can result in a “lag time” between implementing management actions and improvements in water quality.
Goal: The indicator is not related to a goal at this time.
Trends:
What is the long-term trend? (since start of data collection) Between 1938 and 2008, river flow to the Bay has averaged 47.2 BGD and has ranged from 21.9 to 78.2 BGD. The Climate Change and the Chesapeake Bay State-of-the-Science Review and Recommendations: A Report from the Chesapeake Bay Program Science and Technical Advisory Committee (STAC) highlighted an examination of the 1957 to 2000 record of annual streamflow into the Chesapeake and found substantial interannual variability as well as decadal variability characterized by dry conditions during the 1960s, wet conditions during the 1970s, and relatively normal conditions since then. There was no obvious long-term trend.
What is the short-term trend? (10 year trend) The last 10 years have highly variable flow. Between , river flow increased from 21.9 to 37.5 BGD.
Change from previous year: : river flow decreased from 41 to 37.5 BGD.
About half the water in the Bay comes from the rivers, the other half from the ocean.
In an average year, three rivers deliver most (about 81%) of the river flow: Susquehanna (48%), Potomac (19%), and James (14%).
The U.S. Geological Survey, one of the Chesapeake Bay Program federal partners, has been monitoring the volume of freshwater flowing into the Bay – or river flow – from the three biggest rivers concurrently since 1937.
Normal Range
Dry
Years
Data and Methods:
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

12. Weather
Rainfall, temperature and winds have a great impact on water quality, habitats and fish and shellfish populations.
Climate change and variability have caused water temperatures in the Bay to exhibit greater extremes during the 20th century than the previous 2,000 years.
Sea-level rise related to climate change is contributing to the loss of vital coastal wetlands.
Status: Rainfall, temperature and winds have a great impact on water quality, habitats and fish and shellfish populations. Climate change and variability have caused water temperatures in the Bay to exhibit greater extremes during the 20th century than the previous 2,000 years. Sea-level rise related to climate change is contributing to the loss of vital coastal wetlands.
Additional Information:
Rainfall:
Rainfall affects the volume of water flowing into the Bay – or river flow – from its many freshwater streams and rivers.
River flow impacts the amount of pollution delivered to the Bay, the saltiness of Bay waters, and the vertical mixing of oxygen rich surface waters with deeper waters of the Bay.
As river flow increases, its potential to carry increased pollutants from the watershed increases as well.
River flow is generally fast moving and turbulent, mixing the Bay’s waters and capturing oxygen from the air.
Runoff from winter and spring rains deliver loads of sediment and nutrient pollutants to the Bay that drive summer water quality conditions in the Bay. Past observations reveal that summer weather conditions also contribute to summer water quality when intense storms increase erosion, which contributes to poor water clarity and adds to the existing nutrient load in the Bay.
Not all rain water “runs off” the land. Some water seeps into the soil, carrying nutrients into groundwater. The travel time of nutrients through the watershed ranges from weeks to centuries. This can result in a “lag time” between implementing management actions and improvements in water quality.
Temperature:
Changes in water temperature influence when plants and animals feed, reproduce, move locally or migrate. Temperature plays a critical role in determining the amount of dissolved oxygen in the Bay’s waters. High water temperatures may also affect underwater grass beds.
Temperature dramatically changes the rate of chemical and biological reactions within the water. Because the Bay is so shallow, its capacity to store heat over time is relatively small. As a result, water temperature fluctuates throughout the year, ranging from 34 to 84 degrees Fahrenheit. These changes in water temperature influence when plants and animals feed, reproduce, move locally or migrate.
The temperature profile of the Bay is fairly predictable. During spring and summer, surface and shallow waters are warmer than deeper waters, creating two distinct temperature layers. The turbulence of the water can help to break down this layering. In autumn, fresher surface waters cool faster than deeper waters and sink. Vertical mixing of the two water layers occurs rapidly, usually overnight. This mixing moves nutrients up from the bottom, making them available to phytoplankton and other organisms inhabiting upper water levels. This turnover also distributes much-needed dissolved oxygen to deeper waters. During the winter, water temperature is relatively constant from surface to bottom.
Temperature plays a critical role in determining the amount of dissolved oxygen in the Bay’s waters. The colder the water, the more oxygen it can hold. Therefore, the waters of the Chesapeake Bay have a greater capacity to hold dissolved oxygen during the cold winter months than they do during the summer months.
High water temperatures may affect underwater grass beds. Last year, warmer than average water temperatures may have caused the large scale loss of eelgrass in Tangier Sound. And while high temperatures can negatively affect SAV, they aid in the growth of something not so desirable: algae. These tiny plants flourish in the hot summer sun, soaking up rays and nutrients, but often multiplying to unhealthy proportions. These harmful algae blooms can block out sunlight needed by SAV, or produce toxins that kill fish and sicken humans.
Wind:
Wind also plays an important role by mixing the surface of the water and increasing oxygen levels in the Bay.
Just as circulation moves much-needed blood throughout the human body, circulation of water transports plankton, fish eggs, shellfish larvae, sediments, dissolved oxygen, minerals and nutrients throughout the Bay. Circulation is driven primarily by the movements of freshwater from the north and saltwater from the south. Circulation causes nutrients and sediments to be mixed and resuspended. This mixing creates a zone of maximum turbidity that, due to the amount of available nutrients, is often used as a nursery area for fish and other organisms.
Weather can disrupt or reinforce this two-layered circulation pattern. Wind plays a role in the mixing of the Bay's waters. Wind also can raise or lower the level of surface waters and occasionally reverse the direction of flow. Strong northwest winds, associated with high-pressure areas, push water away from the Atlantic Coast, creating exceptionally low tides. Strong northeast winds, associated with low-pressure areas, produce exceptionally high tides.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09

13. Other Pressures Other Pressures
There are several other factors that impact the overall health of the ecosystem. These include:
Climate Change
Invasive Species
Fisheries Harvest and Pressures
Importance
The Chesapeake region has already begun to see the effects of global climate change in the form of sea level rise and higher water temperatures. Scientists predict that climate change could also cause:
A decrease in underwater grasses
More “dead zones” of low oxygen
More annual precipitation and a resulting increase in the flow of pollution
Fewer wintering waterfowl
A change in the plants and animals that live in the area
Invasive species are animals and plants that are not native to their habitat and negatively affect the invaded ecosystem. Once an invasive species population is established it is unlikely to be completely eradicated. In the Bay region there are more than 200 invasive species thought to cause serious problems; the mute swan, nutria, phragmites, purple loosestrife, water chestnut and zebra mussel are the species that pose the greatest threats.
The Bay and its tributaries have historically been rich grounds for commercial and recreational fisheries. Demand for seafood has driven these commercial fisheries, and crabbing and angling have long been popular activities for residents. But these fisheries have put tremendous pressure on the population of key Chesapeake species, such as blue crabs and oysters.
Goal
The indicators are not related to goals at this time.
Chesapeake Bay Health & Restoration Assessment:
Executive Summary
03/10/09