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The Estimated Likelihood of Nutrients and Pesticides in Nontidal Headwater Streams of the Maryland Coastal Plain During Base Flow
Citation:
DENVER, J. M., S. W. ATOR, A. C. NEALE, AND A. M. PITCHFORD. The Estimated Likelihood of Nutrients and Pesticides in Nontidal Headwater Streams of the Maryland Coastal Plain During Base Flow. Presented at The Second Maryland Streams Symposium, Westminster, MD, August 10 - 13, 2005.
Impact/Purpose:
The overarching objective is to develop and test landscape indicator statistical models for condition of streams and aquatic biota in relation to pesticides, nutrients, sediments and toxic substances, nationwide. The indicator models will serve as tools for managers who want consistent methods to compare potential impacts on streams within a biophysical region for differing landscape patterns. To accomplish this objective, several sub objectives will be important:
Develop landscape indicator statistical models of stream vulnerability for selected regions of the U.S., beginning with the Mid-Atlantic Coastal Streams; studies in the Midwest, California, and the Southeast will follow.
Demonstrate the application of the landscape indicator models for the ranking of watersheds, the identification of "hot spots," and the evaluation of management options using projected future scenarios of land use for the study areas selected above.
Develop statistical distributions for physical characteristics of small water bodies for use in OPP modeling.
Leverage resources for this research by incorporating existing data into the model development process, and by sharing field study costs with other projects in the same geographic areas.
This task represents a topic area within the Landscape Sciences research program which is described in A National Assessment of Landscape Change and Impacts to Aquatic Resources. A 10-Year Research Strategy for the Landscape Sciences Program, EPA/600/R-00/001. It also supports the Regional Vulnerability Assessment (ReVA) Program.
Besides being responsive to the Office of Pesticide Programs, this research directly supports long-term goals established in ORD's multi-year research plans related to GPRA Goal 2 (Water Quality) and GPRA Goal 8.1.1 (Sound Science/Ecological Research). Relative to the GPRA Goal 2 multi-year plan, this research will "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors" and "provide the tools to restore and protect aquatic ecosystems and to forecast the ecological, economic, and human health outcomes of alternative solutions" (Long Term Research Goals 2 and 3). Relative to the Goal 8 multi-year plan, this research will develop and demonstrate methods to provide states, tribes, and federal, state and local managers with abilities to: (1) assess the condition of waterbodies in a scientifically-defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales; (2) diagnose cause and forecast future condition in a scientifically defensible fashion to more effectively protect and restore valued ecosystems; and (3) assess current and future ecological conditions, probable causes of impairments, and management alternatives.
Description:
Water quality in nontidal headwater (first-order) streams of the Coastal Plain during base flow in the late winter and spring is related to land use, hydrogeology, and other natural or human influences in contributing watersheds. A random survey of 174 headwater streams of the Mid-Atlantic Coastal Plain (North Carolina through New Jersey) was conducted in 2000 as part of cooperative research between the U.S. Environmental Protection Agency and U.S. Geological Survey. Base flow was selected for sampling to represent an integration of primarily shallow ground water from upstream watersheds, and possible chronic exposures of chemicals to aquatic communities. Nitrate concentrations (as nitrogen) in streams of the Maryland Coastal Plain during base flow were measured as high as 9.7 milligrams per liter (mg/L), with a median of approximately 1 mg/L. The median for the entire Mid-Atlantic Coastal Plain was 0.42 mg/L. Metolachlor, atrazine, and selected metabolites of each are also commonly detectable in stream base flow in Maryland, but concentrations rarely exceed 1 microgram per liter. Stepwise logistic regression models were developed to relate measured water quality to natural and human influences in contributing watersheds using landscape metrics computed from soils, land use, and topographic data. These models estimate the likelihood of selected nutrients and pesticides in base flow in each of more than 9,000 nontidal headwater streams of the Mid-Atlantic Coastal Plain. Streams most likely to contain nitrogen at concentrations exceeding 0.71 mg/L (a recommended regional criterion) during base flow in the Maryland Coastal Plain are typically located in agricultural areas in well-drained parts of the Delmarva Peninsula, or in urban areas along the Fall Line. The likely occurrence of the herbicide metolachlor and its metabolites is related specifically to agricultural areas, particularly on the Delmarva Peninsula. Diazinon, an insecticide, was rarely detected in Coastal Plain streams during base flow, and occurred almost exclusively in urban areas along the Fall Line. These models will enable managers to compare small watersheds and make preliminary decisions about where to allocate resources for additional monitoring or remediation.