Quantifying Past and Future Nitrogen Sources to the Chesapeake Bay Watershed
Abstract
Chesapeake Bay has been adversely affected by elevated nutrient and sediment loads from its watershed. A Total Maximum Daily Load (TMDL) has been established with a goal of improving water quality and restoring the bay ecosystem. Quantifying nutrient sources is complex, challenging efforts to link specific management actions to outcomes. Here, we report on an effort to estimate past, current, and future nitrogen (N) sources in the Chesapeake Bay watershed from 1950 to 2050. These estimates will be applied in a dynamic application of the SPARROW model to explore how variation in N sources within the watershed has affected watershed N loads over time. The principal N sources that were quantified in this effort are: (1) manure from farm animals, (2) agricultural fertilizer, (3) atmospheric deposition, (4) discharge from wastewater treatment plants, and (5) sources originating from urban/suburban land use. For many of these sources, data were available from the Chesapeake Bay Program for the period from the 1980s until recent years. Past estimates back to 1950 were generally derived from known strong associations of various factors with N inputs such as population from the U.S. Census as a predictor of urban N sources and NOx emissions as a predictor of atmospheric N deposition. Future projections to 2050 were based on extrapolation of existing trends or by consideration of the likely future effects of implementing current rules and regulations. For some sources such as manure, multiple future projections were developed, such as +/- 10% and no change to allow exploration through SPARROW modeling of the likely effects on N loads to the bay if various management strategies were implemented to achieve these future changes. In this presentation, the approaches, results, and uncertainties in these estimates of principal N sources will be discussed in the context of their contribution to N loads to the bay and as opportunities for contributing to TMDL goals for restoration of the bay ecosystem.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC54D..17B
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCES;
- 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCES;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE