Predicting nitrogen flow from forested watersheds of the Susquehanna Basin

2007 Impact statement
  • Weinstein, David Alan

abstract

The Regional Nutrient Management model (ReNuMa) uses a relationship predicting nitrogen (N) export from N deposition. I am constructing an alternative method to estimate nitrate export from forested watersheds to increase the accuracy of this prediction. This method uses the model, SINIC (Simple Nitrogen Cycle), to provide a relationship between site conditions and N export that accounts for more of the variables causing export to vary from watershed to watershed and at different times. This method has identified the importance of topography, temperature, moisture, substrate, vegetation on N export. I am currently investigating whether this set of variables must be expanded to work throughout the watersheds of the upper Susquehanna River basin. I am categorizing sub-watersheds of the upper Susquehanna based on similar properties of topography, temperature, moisture, substrate, and vegetation. For a selection of these sub-watersheds, I am producing predictions for inorganic N export.

submitted by

issue being addressed

The Susquehanna River is the largest tributary of Chesapeake Bay, and the single largest source of nutrients to the main stem of the Bay. Excess nutrients are being brought by the river into the Bay, causing rapid deterioration of the bay`s ecosystem. My goal is to gain a better understanding of the sources and sinks of nitrogen (N) in this large rural watershed of mixed land uses, including agricultural and forest lands. Better understanding the sources and sinks of nutrients and sediment in the Susquehanna can lead to better management of nutrient fluxes from the landscape and thus water quality in Chesapeake Bay. This research will also lead to a better understanding of the controls on N pollution in rural landscapes in general.

response

The estimate of the average N export from the entire forested landscape in this study is much higher than reported from previous export predictions made based on deposition alone. This study estimates that 71% of the landscape has higher levels of export than those predicted from deposition alone. The method of estimation reported here considers the diversity of the landscape and the differences in the way that different landscape units are likely to process nitrogen. It considers the nutrient cycles that have developed on each unit in response to the specific environmental conditions occurring there. However, this study ignored the differences between spring and summer export, which may have resulted in extrapolations that high spring export rates are characteristic of rates for the entire year, potentially overestimating the total annual export. A revision of this methodology to account for these temporal changes to avoid this incorrect extrapolation will be implemented in the next step of this work.

impact assessment

Better understanding of the sources nutrients in the Susquehanna can lead towards better management of nutrient fluxes from the landscape and thus water quality in Chesapeake Bay. This research is helping to identify the relative role of forests versus agriculture in controlling N pollution in rural landscapes. These insights will help us identify the importance of implementing N control practices in agriculture in the northeastern United States, and will help us identify the characteristics of watersheds that lead to high N export.

academic priority area

has geographic focus

funding source description

Department of Agriculture

collaborators

  • Upper Susquehanna Coalition
  • Agricultural Ecosystems Program

key personnel

  • Robert Howarth
  • Jim Curatolo

department, unit, division

mission focus

From CALS annual faculty reporting. Imported on August 5, 2008