Assessment and Management Practices: Impact on Health*
Source water protection urgently needs broad regional, state, and national attention to continue to ensure safe drinking water. During the workshop, speakers considered the complexity underlying the assessment of source water protection from a variety of threats, such as land-use patterns, nutrient loading, and agricultural practices.
SOURCE WATER ASSESSMENT AT THE STATE LEVEL
The Safe Drinking Water Act (SWDA) amendments of 1996 required the states to identify areas that provide drinking water, delineate their boundaries, register potential sources, assess their vulnerability to potential contamination, inform the public of the results, and implement a source water protection program, noted Greg Rogers of the Texas Commission on Environmental Quality (TCEQ). The 1996 amendments have included more emphasis on being proactive toward potential problems and involvement by consumers throughout the process.
With the 1996 reauthorization of SWDA, states were challenged to assess drinking water potential with regard to contamination and to develop data that could be used during monitoring. This was a challenge for most states including Texas, which has more than 6,000 water systems, close to 20,000 public water supply wells, and 600 water intakes and contains 10 percent of the nation’s drinking water systems, noted
Rogers. The challenge would be to design a system that would be able to provide accurate assessment from multiple water sources.
In partnership with the U.S. Geological Survey (USGS), Texas began to develop a software system that could assist viable decisions with minimal human error, while ensuring ease of usability. The resulting system connects with the state’s multimillion-record drinking water source and geographical information system (GIS) databases, giving the user a three-dimensional visual snapshot of the location or area of interest. It has enabled, for example, development of the Aquifer Atlas of Texas a mapping of all of the state’s aquifers, including the multilayer aquifers that are common in Texas—derived from properties such as transmissivity, porosity, saturated thickness, and storage capacity. The system is based on accurate location information regarding the state’s numerous public wells, together with details such as a well’s depth, casing, and opening intervals, and it is flexible enough to adjust to various conditions such as a well’s intersecting the bottom of an aquifer. Using these three-dimensional data sets the Texas team was able to model the actual effects of water draw on the aquifers. Thus, TCEQ could get more detailed than the fixed radius approach of the 1986 wellhead protection program.
Surface water assessment was more challenging because of the size of the watershed, which required that Texas look at an area of primary influence (API) or an area of primary concern, noted Rogers. By using a digital elevation model to delineate the watershed of a lake, TCEQ could identify an API, in which it wanted to be aware of potentially catastrophic effects.
To fully assess source water, knowledge of point source and nonpoint source contamination is required. While recognizing that knowing the locations of leaking storage tanks, oil and gas wells, and landfills is important and should continue to be monitored, there also has been recognition that nonpoint source contamination will continue to increase in influence in the future, observed Rogers. To assess the effects of nonpoint sources, TCEQ used multiresolution land classifications (MRLCs)—based on 20 different types of land-uses—that divided Texas into approximately 700 million 100-foot squares. These classifications formed the basis for establishing statistical relationships between land-use and water quality and further allowed for predictable equations in areas where the data were incomplete.
The Texas program is a contaminant specific assessment, which requires cataloguing the locations of potential sources of contamination (e.g., airports, landfills, gas stations) and relating specific chemicals to
each activity. From this catalogue, assessments can be developed by determining how these contamination sources intersect the capture zones. Rogers noted that the assessments include an attenuation component, based on the fact that pollutants from point sources do not always reach the well or water intake. With colleagues from the University of Texas, the program models contamination based on factors such as vertical migration, dilution of the aquifer, and properties of the chemical. Using this information, one can predict that a potential source of contamination will attenuate before it actually makes it to the well.
This software system can have numerous applications for addressing water needs at the state level, noted Rogers. This tool also can help planners look at the situation regionally; given statewide datasets, they can see a much broader picture. In the future, the software system will be used for prioritizing source water protection efforts based for instance on aquifer type, well depth, specific contamination point density, or water quality. In addition, the software and the statewide data sets allow for planning of safe source water by pre-assessing well and water intakes prior to their creation to determine if there are potential problems. As the state system evolves, there will be more local water system involvement, which will form feedback loops that produce the best and most cost-effective results of source water protection, concluded Rogers.
LAND-USE PLANNING: A CONCERN FOR SOURCE WATER PROTECTION?
Local planning is a key tool for ensuring adequate source water. In fact, good land-use planning is a preventive measure that is very protective of public health, said Douglas “Dusty” Hall of Ohio’s Miami Conservancy District. This concept parallels the shift in traditional medicine from treatment to prevention.
An essential component in a holistic approach to planning is widespread community involvement. In Ohio, the flood of 1913 resulted in a broad watershed approach to problem solving by the establishment of Conservancy Districts. The Miami Conservancy District (MCD), which contains approximately 1.5 million people in southwestern Ohio, involves many interrelated initiatives that bear on water resources and quality of life in its communities. Initiatives include
Good land-use planning is a preventive measure that is very protective of public health
flood protection, aquifer preservation, and river corridor improvement, as well as bikeways and other recreational amenities. The MCD, which was created by state statute, operates within a watershed-based boundary and has very broad authorities, including eminent domain. It is governed by a Conservancy Court consisting of one common pleas court judge from each of the counties within the District’s official boundaries. The MCD maintains active relationships with local leaders and has created an extensive market collaborative with different local government entities, from townships to villages to counties to cities. The ability to create dialogue across government to resolve water quality problems is critical to sound water resources management, said Hall.
Meanwhile, according to Hall, MCD’s core group of professional scientists translate knowledge into practice through multiple community-based groups. Virtually the entire watershed is covered by community groups composed of activists, agricultural producers, and others. By building trust through dialogue the District has been able to promote changes in land-use without government regulation.
The MCD’s major metropolitan area, Dayton, provides an example of comprehensive water resources planning and management based on lessons from previous mistakes. When Dayton’s first land-use plan was implemented in 1926, the connection between water resources and planning was not yet fully developed. The result was that the major public drinking water supplier’s well fields were surrounded by manufacturing. Given the proximity of rivers and their utility for receiving industrial discharges the land-use plan deemed these locations well suited for manufacturers’ activities—even though these very same rivers were the principal sources of recharge for the underlying and very sensitive aquifer. Thus, a comprehensive program evolved (see Box 2.1) that recognized these dilemmas and reflected a more balanced approach. Its features include an early-warning monitoring system with extensive groundwater coverage including wells near potential contaminant sources, spill reporting, time-critical response capability, and an overlay zoning district to regulate land-use. This program continues to evolve and be effective; however, changing demographics have given rise to other concerns. Ohio is using up farmland at a rate exceeded only by Texas as urbanites move to the “exurbs” that are forming at the interface between urban/suburban and predominately rural lands. This shift in population has been accompanied by an increasing reliance on household sewage treatment systems
SOURCE: Hall unpublished from presentation
since these areas are often not served by centralized sanitary sewer infrastructure (see Figure 2.1). Ohio’s approach to regulation of household sewage treatment systems results in about 8 percent being subject to oversight. Unfortunately, the Ohio Department of Health estimates that statewide about 900,000 gallons of improperly treated sewage are being discharged each day by failing systems. This situation is exacerbated by the fact that the townships with exurban areas that are experiencing significant new growth, do not have the authority to do comprehensive planning and land-use management like cities such as Dayton. Consequently, some of the most rapidly growing areas within the state have a limited ability to handle the population growth, land-use changes, and resulting source water protection needs, noted Hall.
This is a situation in which policy makers are in danger of repeating past mistakes: they fail to undertake comprehensive land-use planning with water resources in mind. Partnerships are needed—for example, between the American Planning Association (APA) and scientific organizations—to help stakeholders understand the health linkages between shifting population and the need for comprehensive water resources planning and management. Organizations, such as Urban Land Institute, National League of Cities, and university-based urban and regional planning program such as the one at the UCLA Department of Urban Planning have developed best practice guidelines for urban and regional planning that may help to address many of these needs. The
irony, according to Hall, is that some people move out of urban areas because they feel unsafe. But, they move to these exurban areas without fully understanding the different set of challenges for providing drinking water in these formerly rural areas.
IMPACTS OF NONPOINT SOURCE POLLUTION ON DRINKING WATER AND HUMAN HEALTH
Current U.S. Environmental Protection Agency (EPA) estimates suggest that approximately one-third of all assessed rivers, streams, and lakes are impaired, primarily through nonpoint source pollution, said Thomas Christensen of the U.S. Department of Agriculture’s (USDAs) Natural Resources Conservation Service. Although these pollutants come from many sources, agricultural practices are a significant contributor, especially in the Mississippi River basin. He noted that the USDA has a wide range of programs and tools for working with the agricultural community to improve water quality through voluntary nonpoint source management.
Types of Contamination
Agricultural pollutants include sediment, nutrients, pesticides, and pathogens (see Figure 2.2). The total comprehensive assessment of damages from agricultural pollution is lacking, although some estimates suggest that the cost is high. For example, soil erosion from agricultural lands is estimated to cost water users $2 billion to $8 billion annually. Nutrients such as nitrogen and phosphorus contribute to algae blooms, low dissolved oxygen, and potential health effects. Both surface water (runoff) and groundwater (leaching) are affected. In the United States, the Mississippi River basin covering all or part of 31 states has the highest potential run off, which comes from two principal sources, animal manure and inorganic fertilizer. Nationwide, 188 public water systems (serving 748,000 people) reported violations in 1998 of EPA’s nitrate maximum contaminant level.
Pesticides are another potential area of concern in many regions of the country, because many pesticides are suspected carcinogens or neurotoxicants. To date, however, the USGS’ National Water Quality Assessment Program has shown low levels of pesticides in most waterways in agricultural basins, according to Christensen. He noted that integrated pest management plans can now minimize the use of pesticides through the improved timing, efficiency, and appropriateness of their application. Pathogens and pharmaceuticals are emerging water quality concerns and an area in which additional research is needed. Although there are many sources of these contaminants, the principal entry from agricultural practice is through animal wastes.
Programs for Improving Water Quality
Managing these contaminants requires the collaboration of a number of federal, state, and local agencies and many types of programs, noted Christensen, but he stressed that the states have the overall lead in water quality issues. To support the states, the USDA has many conservation programs and often more than one of these programs are employed on a particular farm. For example, in working with landowners and communities, USDA takes a natural resources conservation approach that includes voluntary, incentive-based initiatives; science-based solutions on a site-specific basis; locally led processes; informed landowner as decision
maker; progressive implementation; adaptive management; and regulation where it is needed.
The Conservation Security Program, a new 2002 Farm Bill-specified initiative that will begin in 2004, will allow the USDA to work with farmers and ranchers to reward them for good conservation and further enhance their conservation efforts through a wide array of conservation practices—a system that makes sense for a particular operation, said Christensen. USDA has more than 160 conservation practices; all have technical standards and science behind them, including nutrient and pest management, animal waste storage, grassed waterways, and irrigation water management. These conservation practices, observed Christensen, are analogous to the well-known best management practices (BMPs) for water quality, which derive from the Clean Water Act and deal specifically with water pollution control activities.
Christensen cited a particular case study: an area of 2.2 million acres in West Virginia’s Upper Potomac River basin that has a high concentration of beef and poultry operations, which result in water quality problems from fecal bacteria. An intensive watershed planning process oc-
curred—all done on a voluntary basis with total maximum daily load (TMDL) requirements in the background—that drew on EPA and USDA programs to bring together several sources of funding and technical assistance. The result, Christensen said, was a success story. Voluntary participation on the part of landowners was approximately 85 percent, with many landowners entering into long-term contracts that obligated them to manage their poultry litter. Continued monitoring has shown that the water quality issue of fecal coliform has been reduced, and in fact the stream is now delisted; i.e., no longer on the list of impaired waters.
The USDA’s decades-long involvement in the water quality arena has taught it some important lessons, noted Christensen. First, both economics and social benefits are drivers of clean water activities. Producers must make a reasonable profit to stay in business, and any activity employed has to recognize this. Second, management of land and water resources should be done on a watershed basis. Third, watershed monitoring has to be enhanced. There should be consistent quality monitoring, which will require the collaboration of all stakeholders, both public and private. Fourth, there is a need for access to water quality information and improved decision support tools.
Both economics and social benefits are drivers of clean water activities.
The adoption of BMPs for water quality improvement has its own set of requirements for success, said Christensen. Individual BMPs should be linked with effective outcomes on the quality of water in a specific water body. Similarly, these practices must make economic sense to the producer, he remarked, noting that we have not done enough to identify some of the economic benefits that might occur. Additionally, some work in the area of risk management is necessary. In many cases, producers may be unwilling to reduce the application rate of a fertilizer because they expect a reduced crop yield to result. A risk management policy could be applied: if the yields are reduced, it would make up the difference in lost benefits. Christensen concluded by suggesting that more research will be needed on the effectiveness of BMPs and the development of community-based solutions and market-based opportunities.
NUTRIENT LOADING: CRITICAL LINK IN THE CHAIN
Nutrients are regulated under both the Safe Drinking Water Act and the Clean Water Act and thus, are areas for synergic oversight. As noted above, nitrogen and phosphorus are the two nutrients of concern because of their potential health linkages. In terms of the Clean Water Act, excessive nitrogen and phosphorus loading in surface waters can be important for drinking water through toxic algal growth and the formation of trihalomethanes as a byproduct of disinfection, said Kenneth H.Reckhow of Duke University and the University of North Carolina.
Nutrient loading comes from a variety of both natural and anthropogenic point and nonpoint sources, including decaying plant material, soil erosion, bedrock weathering, wastewater treatment plants, urban runoff, agricultural runoff, and fossil fuel burning (see Figure 2.3). Understanding the processes that affect their transformations and transport has allowed scientists in a laboratory or controlled field setting to assess the critically important rates of reaction. However, despite our extensive general knowledge and awareness of sources, transformations, and transport of nitrogen and phosphorus, predictability becomes weaker when we utilize this scientific knowledge to predict outcomes in specific situations in the real world—for example, a natural water body’s response to management actions such as wastewater treatment or reduction of fertilizer application rates. This can be illustrated by many river basins including North Carolina’s Neuse River, which is the third largest river basin in the state, containing a large urban area with 1.5 million people living within the basin, numerous wastewater treatment plants, and a large number of contained animal feedlot operations (CAFOs).
Because CAFOs are regulated as zero-discharge facilities under the Clean Water Act, the effluent from hog pens is flushed into lagoons to be sprayed by farmers later onto their fields at allowable rates in accordance with guidelines established in consultation with North Carolina State University. There are some difficulties with this process, Reckhow noted, because of the state’s vulnerability to hurricanes and other wet periods. During these times, spills can occur as lagoons breach or break, and even if they remain intact, farmers’ fields become saturated and are not amenable to receiving effluent. The EPA recognizes this problem and is looking into alternatives, Reckhow said, but this remains a major contributor of nitrogen to the Neuse River basin.
As nitrogen is introduced from commercial fertilizers, manure, and wastewater and then transformed, how much of it is volatilized as ammonia and escapes as this gas? How much is denitrified and, therefore, effectively removed from contributing to algal growth in the receiving water body? How much is transported through the ground and moves readily into groundwater as nitrate? Accurate answers to these questions are not readily forthcoming, conceded Reckhow. Scientists know that
these processes occur and understand the science in the reductionist sense at the small scale. Yet when this well-established knowledge from the laboratory and from textbooks is applied on the watershed scale, the current existing models do not provide the necessary reliability for making water quality decisions.
When well-established knowledge from the lab and from textbooks is applied on the watershed scale, the current existing models do not provide the necessary reliability for making water quality decisions.
Reckhow cited two ways in which to make modest reductions in prediction error in the future: advances in scientific knowledge that lead to increasingly elaborate and detailed models, and better observational data and enhancements in statistical techniques for extracting patterns from the data. The problem with current models is that it is difficult to capture the inherent complexity of an aquatic ecosystem and the extreme variability of nature. Yet predictions are nevertheless needed to guide decision making.
Reckhow suggested that scientists need to employ adaptive management by observing how the actual water body responds, and then use this information to augment the predictive power of the model system. He further noted that it is not improvements in models from better science, more detailed mathematics, or better data that will lead to advancement. It is the integration of the monitoring, associated with the post-implementation response of a real system, with the model forecast—an adaptive framework, in which we learn while doing—that should become common practice for these assessments, concluded Reckhow.