| Abstract: |
The combined watershed, hydrodynamic, and eutrophication models currently referred to as the Chesapeake Bay Environmental Model Package (CBEMP) were originated in 1987 and have been in the process of continuous refinement since then. A fundamental purpose of the CBEMP is to represent hypoxia. This representation includes quantifying processes which create hypoxia, reproducing observations of hypoxia, and projecting the outcomes of remediation efforts. The CBEMP has passed through four major development stages. The original stage focused on processes in the water column and benthic sediments and employed tidal average hydrodynamics on a computational grid of 4,000 elements. The second stage increased resolution to 10,000 elements and employed intertidal hydrodynamics. Benthic algae and zooplankton were added to the model computational suite. In the third stage, emphasis on modeled primary production and respiration were coupled with further refined resolution. The most recent stage employs a grid of 50,000 elements and attempts to route the products of primary production on the shoals to deep channel water. Some of the improvements have been more significant than others in improving the model representation of hypoxia. We examine here basic model processes and budgets at each stage of development and compare these to observations and current paradigms regarding hypoxia. Processes which are accurately modeled are identified as well as processes which are not. The presentation paints a picture of the present model status and provides a basis for the next generation of Chesapeake Bay eutrophication models. |
