MODELING, MONITORING, AND RESEARCH APPLIED IN DEVELOPING THE 2003 CHESAPEAKE NUTRIENT AND SEDIMENT ALLOCATIONS

In 2003, the Chesapeake Bay Program completed allocations of nutrient and sediment which will reduce loads of these pollutants to Chesapeake tidal waters. Compared to estimated nutrient loads in 1985, the 2003 allocations will reduce nitrogen loads from 338 million pounds to 175 million pounds, phosphorus from 27 million pounds to13 million pounds, and sediment from 5.8 million tons to 4.1 million tons. This is a relative reduction of 48%, 52%, and 29% for nitrogen, phosphorus, and sediment respectively. These load reductions are estimated to remove all water quality impairments of dissolved oxygen (DO), chlorophyll, and clarity in the Chesapeake.

As an integrator of monitoring and research information, the models of the Chesapeake airshed, watershed, and estuary were used to support the 2003 Allocation decision making.. The models have been applied in the Chesapeake and refined through several versions since 1992, 1982, and 1987 for the airshed , watershed, and estuarine models respectively.

Work now centers on refinement of all these models to better track the nutrient and sediment reductions in the Chesapeake. The Airshed Model is being refined to the second generation of modeling atmospheric deposition of nitrogen, replacing the Regional Acid Deposition Model (RADM) with the Community Multiscale Air Quality Model (CMAQ). The Watershed Model is being refined by a level of spatial detail increase by about an order of magnitude by a group of scientists and engineers from the EPA, USGS, and University of Maryland. Both the airshed and watershed models are specifically designed as community models, allowing open source, public domain code of all preprocessors, postprocessors, and main code. The estuarine model is being refined to include water quality and living resource interaction, particularly through filter feeding organisms and submerged aquatic vegetation (SAV), as well as the simulation of sediment transport.