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The role of wetland water quality standards in nonpoint source pollution control strategies
Ecological Engineering, 1 (1992) 143-148
143
Elsevier Science Publishers B.V., Amsterdam
The role of wetland water quality standards in nonpoint source pollution control strategies Doreen M. Robb US Enuironmental Protection Agency, Office of Wetlands, Oceans, and Watersheds, 401 M Street, SW (A-IO4F), Washington, DC 20460, USA
ABSTRACT States in the United States are required to develop water quality standards for their wetlands by the end of Fiscal Year 1993. Standards are vital to the protection of wetlands from a broad array of perturbations including nonpoint source (NPS) pollution. The natural water quality functions of wetlands make them potential components of NPS control strategies, but protection of wetland structure and functions takes precedence over their use in NPS control. Narrative biological criteria are one part of standards and can serve as a mechanism to address NPS pollution impacts. Criteria can also be used as a baseline to determine the effectiveness of best management practices. Numeric biocriteria are under development and will require additional research. INTRODUCTION
How much of a sediment load can a wetland receive without being degraded? How much phosphorus can an inland marsh assimilate before it eutrophies or changes vegetation type? The answers to questions such as these are vital to those seeking to protect wetlands from nonpoint source (NPS) pollution. Through the proper development and implementation of water quality standards (WQS) for wetlands, states and other governmental units can protect their wetlands and associated water quality functions. This paper will describe the components of WQS, then discuss the transition from narrative biological criteria to numeric biocriteria, and will finish by identifying US Environmental Protection Agency (EPA) and state information needs for further development of WQS. W A T E R Q U A L I T Y S T A N D A R D S F O R WETLANDS
In July of 1990, US EPA published national guidance requiring states to develop WQS for their wetlands by the end of Fiscal Year 1993 (US EPA, Correspondence to: D.M. Robb, US Environmental Protection Agency, Office of Wetlands, Oceans, and Watersheds, 401 M Street, SW (A-104F), Washington, DC 20460, USA. 0925-8574/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
144
D.M. ROBB
1990). This will afford wetlands the same level of protection currently provided to other surface waters. Water quality standards consist of three parts. First, wetlands must have designated uses (e.g., aquatic life support, recreation, floodwater attenuation, groundwater recharge) consistent with the goals of the Clean Water Act. Next, narrative and numeric criteria are assigned to protect those uses. Narrative criteria are statements of attained or attainable conditions of a waterbody, and numeric criteria are numeric, usually chemical, endpoints that specify the maximum contaminant level that can be present without impairing the use of that waterbody. Third, each waterbody must have an antidegradation policy and implementation methods that protect previously existing uses of the waterbody as well as provide additional protection to higher quality and outstanding waters where the quality exceeds that necessary to maintain the uses. Wetland standards are an important tool for states wishing to broaden the protection of their wetlands beyond minimizing the disposal of dredged and fill material as provided for by Section 404 of the Clean Water Act. If implemented aggressively, comprehensive narrative criteria can be used to protect wetlands from physical and hydrological modifications, including increased water flow, sedimentation, and nutrient overenrichment. By establishing criteria for a healthy wetland, a baseline exists against which changes in floral or faunal composition may be detected and evaluated. These baselines provide a basis for monitoring and assessing whether NPS pollution has detrimentally impacted a wetland. These changes can also be indications that best management practices (BMPs) are not achieving the desired result. BMPs can then be strengthened and refined until the waterbody in question is brought into compliance with water quality standards. The information needed to develop wetland standards and criteria will also be useful to designers of constructed wetland treatment systems in defining maximum loading rates for pollutants, and in monitoring system performance. Water quality standards have evolved over the years. Originally, the 1965 Water Quality Act took a water quality-based approach by requiring states to develop WQS that specified levels of cleanliness for waters. Similar in concept to what we have today, numeric chemical criteria were developed to protect waters on a chemical-by-chemical basis. At the time, this water quality approach was not very effective since the necessary program infrastructure to enforce standards was lacking. Subsequently, the 1972 Clean Water Act established a technology-based approach that regulated individual point source discharges through National Pollutant Discharge Elimination System (NPDES) permits. These permits set guidelines for effluent limits and are basically "end-of-pipe" controls. Once the NPDES program was established and enforcement mechanisms were in place, the 1987
R O L E O F W A T E R Q U A L I T Y S T A N D A R D S IN NPS P O L L U T I O N C O N T R O L
145
Clean Water Act (CWA) amendments re-established a water quality-based approach to supplement technology-based controls. BIOLOGICAL CRITERIA
The 1987 Clean Water Act identified remaining serious pollution problems, including toxic pollutants and NPS pollution. NPS impacts include sedimentation, eutrophication, hydrologic modification, bioaccumulation of toxics, increased turbidity and, subsequently, decreased light penetration. These impacts cannot be fully addressed on a chemical-by-chemical basis and can lead to secondary impacts such as changes in vegetation type and associated biota. In an effort to address the primary impacts, EPA and the states have utilized narrative criteria. All states have adopted variations of aesthetic narrative criteria - - the "free froms". "Free froms" are general statements, such as "free from debris, noxious odors, and taste". The development of narrative biological criteria (and numeric biocriteria in future years), however, is a new area of emphasis for EPA that will more effectively address secondary impacts.
Narrative biocriteria The development of narrative biological criteria and their application to NPS issues has important implications for wetlands. Narrative biological criteria are new requirements for all surface waters and are statements of attained or attainable condition necessary to protect the biological integrity of the waterbody. These criteria are flexible and can be written as very general or very specific statements. They can take the form of a "free from" statement, such as "free from activities that would substantially impair the biological community as it naturally occurs due to physical, chemical, and hydrologic changes". In their broadest sense, biological criteria protect the physical and structural components necessary for healthy aquatic habitat as well as the biota. For example, one state used more specific language to protect the natural hydrologic conditions of a wetland:
"Natural hydrological conditions necessary to support the biological and physical characteristics naturally present in wetlands shall be protected to prevent significant adverse impacts on: (1) Water currents, erosion or sedimentation patterns; ... (3) The chemical, nutrient and dissolved oxygen regime of the wetland; (4) The normal movement of aquatic fauna; ... and (6) Normal water levels or elevations [emphasis added]."
146
D.M.ROBB
Narrative biocriteria can be effective in protecting wetlands from adverse impacts of NPS pollution if implemented effectively through BMPs. The examples described above are good first steps, and provide greater protection to wetlands than existed through numeric chemical criteria, but they have limitations and are difficult to enforce. A key point, however, is that the development of narrative biological criteria by states is based only on existing (and defensible) scientific information. For this reason, states should not have difficulty in developing narrative biocriteria immediately. Numeric biocriteria The next step after the development of narrative biocriteria, however, is the development of numeric biocriteria. This is a future emphasis for EPA and the states and is based on the development of new scientific information. Numeric biocriteria have the potential to be more protective than narrative criteria because they are "hard" numbers and less subject to interpretation; therefore, they should be easier to enforce consistently. Currently, EPA is working on national guidance for rivers and streams; development of guidance for wetlands is slated for the future. An example of a numeric biocriterion for a coastal state is "vegetative diversity no greater than 2 species for salt marshes and no fewer than 25 species for a freshwater inland marsh" or "percent vegetative species change shall be no greater than 10 percent". Similar numbers could be derived for other components of the biota, such as benthic invertebrates, breeding birds, and amphibians. NPS CONTROLS AND WETLAND WATER QUALITY STANDARDS Wetlands have an important role in the landscape through their ability to improve water quality by filtering, transforming, and accumulating pollutants and thereby protecting adjacent rivers, lakes, and streams. This "buffering" function, however, also encourages overuse, and this overuse can compromise these and other wetland functions, such as wildlife habitat and aesthetic and recreational values. While wetlands may be useful components of NPS pollution control strategies, the first goal must be protection of wetlands from pollution. EPA does not allow surface waters to be used as disposal sites for wastewater, and state water quality standards exist to ensure the protection of state waters, including wetlands. Consider the following examples: a state restores a degraded wetland for the purpose of slowing water that will flow from a new parking lot or highway, or a private landowner restores a degraded riparian area for the purpose of filtering sediment and nitrogen-enriched water from a nearby
R O L E OF W A T E R Q U A L I T Y S T A N D A R D S IN NPS P O L L U T I O N C O N T R O L
147
feedlot. At first glance, the "use" of a restored wetland in both of these examples protects the water quality of a nearby waterbody such as a lake or stream and that waterbody meets state water quality standards. However, in the case of the highway, toxics accumulate in the wetland in amounts that exceed toxics criteria, and in the feedlot example, the riparian area retains sediment that eventually modifies the flow of water through that area, changing vegetation and runoff patterns. In both of these examples, although the action benefitted the adjacent waterbody, it did so at the expense of the wetland and, therefore, those actions violated the water quality standards. Additional management practices may need to be put in place, such as vegetated grass filter strips to buffer the wetlands. Regardless of the solution used, the integrity of both the wetland and the adjacent waterbody must be protected. MONITORING AND ASSESSMENT
State standards, however, are only one mechanism to control and minimize the degradation of wetlands by NPS pollution. The ability to detect impacts through biological monitoring is another important tool to prevent degradation and is critical to the effective use of water quality standards. Biological monitoring and assessment enables states to compile baseline information on wetland condition. This information can then be used in developing biological criteria. Once a state has established biological criteria for its wetlands, the state then has a regulatory mechanism to deal with impacts that violate state water quality standards. Before states can establish a monitoring program for their wetlands, however, they need to know what to measure (i.e., indicators) and how to recognize an impact. For example, if a state knows it must sample a particular benthic invertebrate, it also needs to know what should be the expected population dynamics of that invertebrate in a particular type of wetland under "natural" and " p e r t u r b e d " conditions. It needs to know whether a change in vegetation is a natural community succession or an indicator of increased phosphorus loading causing an extremely diverse plant community to shift to a monotypic community. Such information will enable states to establish a wetlands monitoring program as well as aid them in future numeric biocriteria development. F U T U R E RESEARCH NEEDS
As states work to establish narrative biological criteria, US E P A will be developing guidance for developing numeric biological criteria. Increasing
148
D.M. ROBB
the technical science base is necessary before numeric biocriteria can be developed. Examples of important research questions include: • How do altered hydrology and sedimentation patterns impact wetlands and how does the biological community react to these changes? • What should states measure to discern these changes? • How much change is too much? Such information is needed for all wetland types and regions so states can monitor for and recognize these impacts when they occur. CONCLUSIONS Wetlands have an important function in landscape water quality. As a result, they are often included in strategies for controlling NPS pollution. Water quality standards, however, apply to wetlands as well as to other waterbodies. Therefore, wetlands must be protected from NPS pollution through, for example, the use of BMPs such as upland buffers. State development of effective water quality standards for wetlands requires further research on indicators of wetland health, impacts and indicators of physical and hydrological alterations, and thresholds for sediment, nutrients, and toxics loading. These types of information will enable states to protect their wetlands through technically defensible water quality standards. REFERENCE US Environmental Protection Agency, 1990. Water Quality Standards for Wetlands: National Guidance. EPA 440/S-90-011. Office of Water Regulations and Standards, US EPA, Washington, DC.
143
Elsevier Science Publishers B.V., Amsterdam
The role of wetland water quality standards in nonpoint source pollution control strategies Doreen M. Robb US Enuironmental Protection Agency, Office of Wetlands, Oceans, and Watersheds, 401 M Street, SW (A-IO4F), Washington, DC 20460, USA
ABSTRACT States in the United States are required to develop water quality standards for their wetlands by the end of Fiscal Year 1993. Standards are vital to the protection of wetlands from a broad array of perturbations including nonpoint source (NPS) pollution. The natural water quality functions of wetlands make them potential components of NPS control strategies, but protection of wetland structure and functions takes precedence over their use in NPS control. Narrative biological criteria are one part of standards and can serve as a mechanism to address NPS pollution impacts. Criteria can also be used as a baseline to determine the effectiveness of best management practices. Numeric biocriteria are under development and will require additional research. INTRODUCTION
How much of a sediment load can a wetland receive without being degraded? How much phosphorus can an inland marsh assimilate before it eutrophies or changes vegetation type? The answers to questions such as these are vital to those seeking to protect wetlands from nonpoint source (NPS) pollution. Through the proper development and implementation of water quality standards (WQS) for wetlands, states and other governmental units can protect their wetlands and associated water quality functions. This paper will describe the components of WQS, then discuss the transition from narrative biological criteria to numeric biocriteria, and will finish by identifying US Environmental Protection Agency (EPA) and state information needs for further development of WQS. W A T E R Q U A L I T Y S T A N D A R D S F O R WETLANDS
In July of 1990, US EPA published national guidance requiring states to develop WQS for their wetlands by the end of Fiscal Year 1993 (US EPA, Correspondence to: D.M. Robb, US Environmental Protection Agency, Office of Wetlands, Oceans, and Watersheds, 401 M Street, SW (A-104F), Washington, DC 20460, USA. 0925-8574/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
144
D.M. ROBB
1990). This will afford wetlands the same level of protection currently provided to other surface waters. Water quality standards consist of three parts. First, wetlands must have designated uses (e.g., aquatic life support, recreation, floodwater attenuation, groundwater recharge) consistent with the goals of the Clean Water Act. Next, narrative and numeric criteria are assigned to protect those uses. Narrative criteria are statements of attained or attainable conditions of a waterbody, and numeric criteria are numeric, usually chemical, endpoints that specify the maximum contaminant level that can be present without impairing the use of that waterbody. Third, each waterbody must have an antidegradation policy and implementation methods that protect previously existing uses of the waterbody as well as provide additional protection to higher quality and outstanding waters where the quality exceeds that necessary to maintain the uses. Wetland standards are an important tool for states wishing to broaden the protection of their wetlands beyond minimizing the disposal of dredged and fill material as provided for by Section 404 of the Clean Water Act. If implemented aggressively, comprehensive narrative criteria can be used to protect wetlands from physical and hydrological modifications, including increased water flow, sedimentation, and nutrient overenrichment. By establishing criteria for a healthy wetland, a baseline exists against which changes in floral or faunal composition may be detected and evaluated. These baselines provide a basis for monitoring and assessing whether NPS pollution has detrimentally impacted a wetland. These changes can also be indications that best management practices (BMPs) are not achieving the desired result. BMPs can then be strengthened and refined until the waterbody in question is brought into compliance with water quality standards. The information needed to develop wetland standards and criteria will also be useful to designers of constructed wetland treatment systems in defining maximum loading rates for pollutants, and in monitoring system performance. Water quality standards have evolved over the years. Originally, the 1965 Water Quality Act took a water quality-based approach by requiring states to develop WQS that specified levels of cleanliness for waters. Similar in concept to what we have today, numeric chemical criteria were developed to protect waters on a chemical-by-chemical basis. At the time, this water quality approach was not very effective since the necessary program infrastructure to enforce standards was lacking. Subsequently, the 1972 Clean Water Act established a technology-based approach that regulated individual point source discharges through National Pollutant Discharge Elimination System (NPDES) permits. These permits set guidelines for effluent limits and are basically "end-of-pipe" controls. Once the NPDES program was established and enforcement mechanisms were in place, the 1987
R O L E O F W A T E R Q U A L I T Y S T A N D A R D S IN NPS P O L L U T I O N C O N T R O L
145
Clean Water Act (CWA) amendments re-established a water quality-based approach to supplement technology-based controls. BIOLOGICAL CRITERIA
The 1987 Clean Water Act identified remaining serious pollution problems, including toxic pollutants and NPS pollution. NPS impacts include sedimentation, eutrophication, hydrologic modification, bioaccumulation of toxics, increased turbidity and, subsequently, decreased light penetration. These impacts cannot be fully addressed on a chemical-by-chemical basis and can lead to secondary impacts such as changes in vegetation type and associated biota. In an effort to address the primary impacts, EPA and the states have utilized narrative criteria. All states have adopted variations of aesthetic narrative criteria - - the "free froms". "Free froms" are general statements, such as "free from debris, noxious odors, and taste". The development of narrative biological criteria (and numeric biocriteria in future years), however, is a new area of emphasis for EPA that will more effectively address secondary impacts.
Narrative biocriteria The development of narrative biological criteria and their application to NPS issues has important implications for wetlands. Narrative biological criteria are new requirements for all surface waters and are statements of attained or attainable condition necessary to protect the biological integrity of the waterbody. These criteria are flexible and can be written as very general or very specific statements. They can take the form of a "free from" statement, such as "free from activities that would substantially impair the biological community as it naturally occurs due to physical, chemical, and hydrologic changes". In their broadest sense, biological criteria protect the physical and structural components necessary for healthy aquatic habitat as well as the biota. For example, one state used more specific language to protect the natural hydrologic conditions of a wetland:
"Natural hydrological conditions necessary to support the biological and physical characteristics naturally present in wetlands shall be protected to prevent significant adverse impacts on: (1) Water currents, erosion or sedimentation patterns; ... (3) The chemical, nutrient and dissolved oxygen regime of the wetland; (4) The normal movement of aquatic fauna; ... and (6) Normal water levels or elevations [emphasis added]."
146
D.M.ROBB
Narrative biocriteria can be effective in protecting wetlands from adverse impacts of NPS pollution if implemented effectively through BMPs. The examples described above are good first steps, and provide greater protection to wetlands than existed through numeric chemical criteria, but they have limitations and are difficult to enforce. A key point, however, is that the development of narrative biological criteria by states is based only on existing (and defensible) scientific information. For this reason, states should not have difficulty in developing narrative biocriteria immediately. Numeric biocriteria The next step after the development of narrative biocriteria, however, is the development of numeric biocriteria. This is a future emphasis for EPA and the states and is based on the development of new scientific information. Numeric biocriteria have the potential to be more protective than narrative criteria because they are "hard" numbers and less subject to interpretation; therefore, they should be easier to enforce consistently. Currently, EPA is working on national guidance for rivers and streams; development of guidance for wetlands is slated for the future. An example of a numeric biocriterion for a coastal state is "vegetative diversity no greater than 2 species for salt marshes and no fewer than 25 species for a freshwater inland marsh" or "percent vegetative species change shall be no greater than 10 percent". Similar numbers could be derived for other components of the biota, such as benthic invertebrates, breeding birds, and amphibians. NPS CONTROLS AND WETLAND WATER QUALITY STANDARDS Wetlands have an important role in the landscape through their ability to improve water quality by filtering, transforming, and accumulating pollutants and thereby protecting adjacent rivers, lakes, and streams. This "buffering" function, however, also encourages overuse, and this overuse can compromise these and other wetland functions, such as wildlife habitat and aesthetic and recreational values. While wetlands may be useful components of NPS pollution control strategies, the first goal must be protection of wetlands from pollution. EPA does not allow surface waters to be used as disposal sites for wastewater, and state water quality standards exist to ensure the protection of state waters, including wetlands. Consider the following examples: a state restores a degraded wetland for the purpose of slowing water that will flow from a new parking lot or highway, or a private landowner restores a degraded riparian area for the purpose of filtering sediment and nitrogen-enriched water from a nearby
R O L E OF W A T E R Q U A L I T Y S T A N D A R D S IN NPS P O L L U T I O N C O N T R O L
147
feedlot. At first glance, the "use" of a restored wetland in both of these examples protects the water quality of a nearby waterbody such as a lake or stream and that waterbody meets state water quality standards. However, in the case of the highway, toxics accumulate in the wetland in amounts that exceed toxics criteria, and in the feedlot example, the riparian area retains sediment that eventually modifies the flow of water through that area, changing vegetation and runoff patterns. In both of these examples, although the action benefitted the adjacent waterbody, it did so at the expense of the wetland and, therefore, those actions violated the water quality standards. Additional management practices may need to be put in place, such as vegetated grass filter strips to buffer the wetlands. Regardless of the solution used, the integrity of both the wetland and the adjacent waterbody must be protected. MONITORING AND ASSESSMENT
State standards, however, are only one mechanism to control and minimize the degradation of wetlands by NPS pollution. The ability to detect impacts through biological monitoring is another important tool to prevent degradation and is critical to the effective use of water quality standards. Biological monitoring and assessment enables states to compile baseline information on wetland condition. This information can then be used in developing biological criteria. Once a state has established biological criteria for its wetlands, the state then has a regulatory mechanism to deal with impacts that violate state water quality standards. Before states can establish a monitoring program for their wetlands, however, they need to know what to measure (i.e., indicators) and how to recognize an impact. For example, if a state knows it must sample a particular benthic invertebrate, it also needs to know what should be the expected population dynamics of that invertebrate in a particular type of wetland under "natural" and " p e r t u r b e d " conditions. It needs to know whether a change in vegetation is a natural community succession or an indicator of increased phosphorus loading causing an extremely diverse plant community to shift to a monotypic community. Such information will enable states to establish a wetlands monitoring program as well as aid them in future numeric biocriteria development. F U T U R E RESEARCH NEEDS
As states work to establish narrative biological criteria, US E P A will be developing guidance for developing numeric biological criteria. Increasing
148
D.M. ROBB
the technical science base is necessary before numeric biocriteria can be developed. Examples of important research questions include: • How do altered hydrology and sedimentation patterns impact wetlands and how does the biological community react to these changes? • What should states measure to discern these changes? • How much change is too much? Such information is needed for all wetland types and regions so states can monitor for and recognize these impacts when they occur. CONCLUSIONS Wetlands have an important function in landscape water quality. As a result, they are often included in strategies for controlling NPS pollution. Water quality standards, however, apply to wetlands as well as to other waterbodies. Therefore, wetlands must be protected from NPS pollution through, for example, the use of BMPs such as upland buffers. State development of effective water quality standards for wetlands requires further research on indicators of wetland health, impacts and indicators of physical and hydrological alterations, and thresholds for sediment, nutrients, and toxics loading. These types of information will enable states to protect their wetlands through technically defensible water quality standards. REFERENCE US Environmental Protection Agency, 1990. Water Quality Standards for Wetlands: National Guidance. EPA 440/S-90-011. Office of Water Regulations and Standards, US EPA, Washington, DC.