Potomac Highlands Watershed School

WV Potomac Tributary Strategy: Chapter 4.

  SOURCES OF NUTRIENTS AND SEDIMENT

Excerpted with Permission from the WVPTS Final Version – August 2005

CHAPTER 4 - at a glance…

· Most nutrients from point sources come from municipal and poultry processing wastewater treatment plants.

· Point source nutrients declined 33% in nitrogen and 53% in phosphorus between 1985 and 2002 in the Chesapeake Bay watershed.

· Point source and urban non point source nutrient pollution will increase in importance as the region’s population grows.

· Estimating nutrient and sediment loads from non point sources is difficult.

· Loads from agriculture, urban lawns and atmospheric deposition can be estimated from the scientific literature.

· Loads from certain sources, such as dirt roads, failing stream banks, untreated sewage, and wildlife cannot currently be estimated and need to be assessed.

Nutrients, such as nitrogen and phosphorus, occur naturally in soil, water and the atmosphere, and are required for the growth of plants.  Nutrients are essential to all plant life in the Bay ecosystem, but an excess of nutrients is harmful. When the Bay was surrounded primarily by forest and wetlands, nutrients and sediment were mostly held in place by natural vegetation and relatively little flowed from the watershed into the Bay.  Today, farms, cities and suburbs have replaced many of the original forests and wetlands. These changes in land use and increases in population have dramatically increased the amount of nutrients and sediment entering the Bay's waters.  The sources are many: wastewater treatment plants, industries, vehicle exhaust, acid rain, and runoff from agricultural, residential and urban areas contribute nutrients to the Chesapeake Bay and its rivers.  Bare ground from construction, farming and forestry, and denuded stream banks add to the sediment loads.  This section will discuss the likely sources of nutrient and sediment loads to the Bay, and uncertainties associated with apportioning those loads among sources.

Point Sources

The nutrient loads delivered from large point sources are generally a known quantity, based on extensive monitoring at many point source facilities and by applying lessons learned from facilities where routine nutrient monitoring occurs to those where it does not.  A large portion of the nutrients from point sources comes from  domestic wastewater treatment plants.  As long as the number of people served, daily flow, and level of treatment is known, a reasonable estimate of nutrients delivered to streams can be calculated.  Another important source of nutrients from permitted facilities, in some areas, is animal and food processing facilities. Certain point sources, such as trout rearing facilities and quarries, can be a source of sediment.  In addition, construction sites one acre or larger are regulated as point sources and, if poorly managed, can deliver large quantities of sediment to our waters.  

As a result of rapidly improving technologies, and the funding to install those technologies, there was a 33% decline in nitrogen and a 53% decline in phosphorus delivered to the Bay from all point source facilities in the Chesapeake Bay watershed between 1985 and 2002 (in spite of a 19% increase in population during that time).  The decline in phosphorus may also, in part, be due to region-wide bans on phosphate detergents (note: WV has not banned phosphate detergents).  However, due to population growth, point source phosphorus loads have begun to creep upward. 14  Inevitably, nutrient pollution from wastewater treatment plants and other point sources will continue to increase in importance as the region’s population continues to grow.  The future of the Bay will depend on continuing development and implementation of the highest levels of nutrient reduction practicable from these sources.

 According to the Chesapeake Bay model, WV point sources contributed 16% less nitrogen to the Bay in 2002 than in 1985.  Unfortunately, during this same period the model estimates that phosphorus loads increased by 29%. 

 Non Point Sources

While the science behind predicting nutrient loads from point sources is relatively straightforward, the same cannot always be said for non point sources of nutrients and sediment.

One of the first challenges is to know where both manmade and natural nutrients in a watershed are found, and how much phosphorus and nitrogen is being imported into a watershed.  Importation of nutrients is important, because it adds to the pool of nutrients available to wash into streams and on to the Chesapeake Bay.  The foods that we eat and the nutrients in feed for animals in the agricultural industry are mostly imported. The nutrients in these foods are introduced into the environment via various waste streams –either septic tanks or wastewater treatment plants for people, fertilizers, and agricultural manure applied to fields.

Another term for imported nutrients is nutrient inputs.  The US Geological Survey estimates that atmospheric deposition, animal manure, and commercial fertilizers comprise 97 percent of the total N inputs to West Virginia’s Valley and Ridge province (at 57, 26 and 14% of total N inputs, respectively).  Ninety-five percent of total P inputs come from commercial fertilizer (39%) and animal manure (56%). 15  The atmospheric deposition portion is coming from a mixture of point sources, such as power plants, and non point sources such as automobiles.  Nutrients in fertilizer are entirely imported into this region, while some of the nutrients in manure are part of the “within watershed” nutrient cycle and some are imported in feed or as fertilizer to grow feed.

A great deal is known about some of these nutrient sources and how they behave in the landscape.  For example, commercial fertilizer and animal manure are applied at the heaviest rates along the flood plain, particularly on cropland. 16 Where animal manure is an important source of agricultural fertilizer, as it is in West Virginia’s Potomac watershed, phosphorus tends to accumulate in the soils over time.  This occurs because animal manure typically has a nitrogen (N) to phosphorus (P) ratio of 3:1, while most grain and hay crops utilize N and P at a ratio of about 8:1.  Because manure is typically applied at rates calibrated to meet crop nitrogen needs, phosphorus inevitably builds up in the soil.  However, the water quality problems that might be associated with this buildup are alleviated, at least in part, by the very high capacity of many WV soils to store phosphorus. 17  Ultimately, the capacity of these soils to store phosphorus may be exceeded and phosphorus related water quality problems will become more evident in our waters.

The nitrogen that is applied to soils and not incorporated into plant material moves into our streams readily, as nitrate, with both overland flow and through the soil profile; this accounts for strong correlations between row crops and nitrogen in area streams. 18  On the other hand, regularly elevated P concentrations are often associated with point source discharges from large wastewater treatment plants, generally not with non point sources such as agriculture and fertilized lawns. 19 Non point phosphorus mostly becomes “tied up” in our soils and plants, and moves into streams only during severe storms.  In fact, over 90% of the annual phosphorus load can be delivered during a few severe weather events each year, 20 making it very difficult to quantify.

Atmospheric deposition of nitrogen is more evenly distributed throughout the watershed. It is generally believed that, in this region at least, our abundant forests still have substantial capacity to store additional nitrogen deposited from the atmosphere.  Nitrogen falling on non-forested lands becomes a source of fertilizer and part of the nutrient cycle there.  Nitrogen deposited on water immediately becomes part of the problem.

What it means: Impervious Surface

Impervious surfaces are surfaces that do not allow water to penetrate, like rooftops, roads, and parking lots.  Instead of soaking into the ground, water falling on impervious surfaces moves rapidly across the landscape, increasing erosion and transporting pollutants to streams.  

Urban and suburban development can have a profound influence on water quality.  Decreases in vegetative cover and increases in impervious surfaces dramatically alter the hydrologic cycle, such as increasing the amount of stormwater and surface runoff, and decreasing groundwater recharge and infiltration.  In addition, overuse of fertilizers on residential lands and managed areas like golf courses contribute to the problem.

While nitrogen, phosphorus and sediment loads from agriculture, lawns and atmospheric deposition might reasonably be predicted from the scientific literature, there are important unknowns.  Unknowns include:

· The issue of the dirt roads that are so common in this region.  Simply put, no one knows how much of the sediment seen in our streams following heavy precipitation is coming from erosion of dirt roads - or from construction activities, forestry, riverside camps, and mining. 

· Poorly vegetated, failing stream banks lead to loss of land throughout the Chesapeake Bay watershed.  These failing banks contribute sediment and associated nutrients during and following high water events.  No one knows how much of the sediment in our streams comes from this source.

· Cacapon Institute discovered that some native WV soils are high in phosphorus. 21  Erosion of these soils due to poor land management practices has the potential to contribute significantly to the phosphorus load carried in our streams, and it is often difficult to distinguish between P losses from manure, fertilizer and native soil. 22

· Some are also concerned over the possible role that abundant wildlife, such as deer and geese, might have in transferring excess nutrients to streams.

Trends in Nutrient Pollution in the Chesapeake Bay Watershed

The Chesapeake Bay Program notes the following major trends in sources of nutrients:

· “Nutrients from septic systems are increasing throughout the watershed as development spreads farther into the countryside, beyond the reach of centralized sewer systems.

· Stormwater runoff from urban and suburban areas is increasing as more land is developed.

· Nitrogen from wastewater treatment plants is declining in rivers where enhanced nutrient removal (ENR) technology is being used. It is increasing in other rivers.

· Phosphorus from sewage treatment plants has declined sharply, in large part because of the phosphate detergent ban. (New evidence indicates that phosphorus from point sources went down until 1999 but has since been going up.  Importantly, West Virginia has never passed a phosphate ban.)

· Among the major land use categories, urban and suburban lands contribute, per acre, the largest amount of nutrients to the Bay when septic and wastewater treatment plant discharges are factored in.

· Runoff from farms is generally declining as farmers adopt nutrient management and runoff control techniques, and because the overall amount of farmland is declining.” 23

How does the Bay Program know these things? To the greatest extent possible, the CBP uses real world measurements to assess conditions in the Bay watershed.  For example, it uses actual flow data from wastewater treatment plants to estimate loads from those sources and uses water quality monitoring data, where it exists, to determine what has happened in the past and is happening today.   Where water monitoring data does not exist, and where questions concern future conditions, the CBP uses predictive models to supply answers. 

As was noted in Chapter 3, West Virginia currently lacks the type of water quality data needed to accurately assess our contribution to the Bay’s pollution problems.  For that reason, the WVPTS stakeholders have been largely dependent on the CBP’s models to furnish the information needed to make decisions.  As a number of the WVPTS stakeholders consider these models to be fatally flawed, this has proven to be a source of contention in the process of developing strategies.  However, as the models are central to the tributary strategy process, Chapter 5 describes how these models work and the kind of information they provide. 

the Bay will depend on continuing development and implementation of the highest levels of nutrient reduction practicable from these sources.

 According to the Chesapeake Bay model, WV point sources contributed 16% less nitrogen to the Bay in 2002 than in 1985.  Unfortunately, during this same period the model estimates that phosphorus loads increased by 29%. 

 Non Point Sources

While the science behind predicting nutrient loads from point sources is relatively straightforward, the same cannot always be said for non point sources of nutrients and sediment.

One of the first challenges is to know where both manmade and natural nutrients in a watershed are found, and how much phosphorus and nitrogen is being imported into a watershed.  Importation of nutrients is important, because it adds to the pool of nutrients available to wash into streams and on to the Chesapeake Bay.  The foods that we eat and the nutrients in feed for animals in the agricultural industry are mostly imported. The nutrients in these foods are introduced into the environment via various waste streams –either septic tanks or wastewater treatment plants for people, fertilizers, and agricultural manure applied to fields.

Another term for imported nutrients is nutrient inputs.  The US Geological Survey estimates that atmospheric deposition, animal manure, and commercial fertilizers comprise 97 percent of the total N inputs to West Virginia’s Valley and Ridge province (at 57, 26 and 14% of total N inputs, respectively).  Ninety-five percent of total P inputs come from commercial fertilizer (39%) and animal manure (56%). 15  The atmospheric deposition portion is coming from a mixture of point sources, such as power plants, and non point sources such as automobiles.  Nutrients in fertilizer are entirely imported into this region, while some of the nutrients in manure are part of the “within watershed” nutrient cycle and some are imported in feed or as fertilizer to grow feed.

A great deal is known about some of these nutrient sources and how they behave in the landscape.  For example, commercial fertilizer and animal manure are applied at the heaviest rates along the flood plain, particularly on cropland. 16 Where animal manure is an important source of agricultural fertilizer, as it is in West Virginia’s Potomac watershed, phosphorus tends to accumulate in the soils over time.  This occurs because animal manure typically has a nitrogen (N) to phosphorus (P) ratio of 3:1, while most grain and hay crops utilize N and P at a ratio of about 8:1.  Because manure is typically applied at rates calibrated to meet crop nitrogen needs, phosphorus inevitably builds up in the soil.  However, the water quality problems that might be associated with this buildup are alleviated, at least in part, by the very high capacity of many WV soils to store phosphorus. 17  Ultimately, the capacity of these soils to store phosphorus may be exceeded and phosphorus related water quality problems will become more evident in our waters.

The nitrogen that is applied to soils and not incorporated into plant material moves into our streams readily, as nitrate, with both overland flow and through the soil profile; this accounts for strong correlations between row crops and nitrogen in area streams. 18  On the other hand, regularly elevated P concentrations are often associated with point source discharges from large wastewater treatment plants, generally not with non point sources such as agriculture and fertilized lawns. 19 Non point phosphorus mostly becomes “tied up” in our soils and plants, and moves into streams only during severe storms.  In fact, over 90% of the annual phosphorus load can be delivered during a few severe weather events each year, 20 making it very difficult to quantify.

Atmospheric deposition of nitrogen is more evenly distributed throughout the watershed. It is generally believed that, in this region at least, our abundant forests still have substantial capacity to store additional nitrogen deposited from the atmosphere.  Nitrogen falling on non-forested lands becomes a source of fertilizer and part of the nutrient cycle there.  Nitrogen deposited on water immediately becomes part of the problem.

Urban and suburban development can have a profound influence on water quality.  Decreases in vegetative cover and increases in impervious surfaces dramatically alter the hydrologic cycle, such as increasing the amount of stormwater and surface runoff, and decreasing groundwater recharge and infiltration.  In addition, overuse of fertilizers on residential lands and managed areas like golf courses contribute to the problem.

While nitrogen, phosphorus and sediment loads from agriculture, lawns and atmospheric deposition might reasonably be predicted from the scientific literature, there are important unknowns.  Unknowns include:

· The issue of the dirt roads that are so common in this region.  Simply put, no one knows how much of the sediment seen in our streams following heavy precipitation is coming from erosion of dirt roads - or from construction activities, forestry, riverside camps, and mining. 

· Poorly vegetated, failing stream banks lead to loss of land throughout the Chesapeake Bay watershed.  These failing banks contribute sediment and associated nutrients during and following high water events.  No one knows how much of the sediment in our streams comes from this source.

· Cacapon Institute discovered that some native WV soils are high in phosphorus. 21  Erosion of these soils due to poor land management practices has the potential to contribute significantly to the phosphorus load carried in our streams, and it is often difficult to distinguish between P losses from manure, fertilizer and native soil. 22

· Some are also concerned over the possible role that abundant wildlife, such as deer and geese, might have in transferring excess nutrients to streams.

Trends in Nutrient Pollution in the Chesapeake Bay Watershed

The Chesapeake Bay Program notes the following major trends in sources of nutrients:

· “Nutrients from septic systems are increasing throughout the watershed as development spreads farther into the countryside, beyond the reach of centralized sewer systems.

· Stormwater runoff from urban and suburban areas is increasing as more land is developed.

· Nitrogen from wastewater treatment plants is declining in rivers where enhanced nutrient removal (ENR) technology is being used. It is increasing in other rivers.

· Phosphorus from sewage treatment plants has declined sharply, in large part because of the phosphate detergent ban. (New evidence indicates that phosphorus from point sources went down until 1999 but has since been going up.  Importantly, West Virginia has never passed a phosphate ban.)

· Among the major land use categories, urban and suburban lands contribute, per acre, the largest amount of nutrients to the Bay when septic and wastewater treatment plant discharges are factored in.

· Runoff from farms is generally declining as farmers adopt nutrient management and runoff control techniques, and because the overall amount of farmland is declining.” 23

How does the Bay Program know these things? To the greatest extent possible, the CBP uses real world measurements to assess conditions in the Bay watershed.  For example, it uses actual flow data from wastewater treatment plants to estimate loads from those sources and uses water quality monitoring data, where it exists, to determine what has happened in the past and is happening today.   Where water monitoring data does not exist, and where questions concern future conditions, the CBP uses predictive models to supply answers. 

As was noted in Chapter 3, West Virginia currently lacks the type of water quality data needed to accurately assess our contribution to the Bay’s pollution problems.  For that reason, the WVPTS stakeholders have been largely dependent on the CBP’s models to furnish the information needed to make decisions.  As a number of the WVPTS stakeholders consider these models to be fatally flawed, this has proven to be a source of contention in the process of developing strategies.  However, as the models are central to the tributary strategy process, Chapter 5 describes how these models work and the kind of information they provide models to supply answers. 

As was noted in Chapter 3, West Virginia currently lacks the type of water quality data needed to accurately assess our contribution to the Bay’s pollution problems.  For that reason, the WVPTS stakeholders have been largely dependent on the CBP’s models to furnish the information needed to make decisions.  As a number of the WVPTS stakeholders consider these models to be fatally flawed, this has proven to be a source of contention in the process of developing strategies.  However, as the models are central to the tributary strategy process, Chapter 5 describes how these models work and the kind of information they provide