Managing for water clarity in Chesapeake Bay

Diminished clarity has been listed as a water quality impairment in Chesapeake Bay. The CE-QUAL-ICM eutrophication model has been revised and recalibrated to provide management guidance in alleviating impaired clarity. The algorithms used to model light attenuation and suspended solids are presented herein. Computed and observed total and volatile solids and light attenuation are examined in several formats. A solids budget constructed for the bay identifies major solids sources as internal production, bank erosion, and watershed loading. Sensitivity to loading sources and a key management scenario are examined. Major but feasible reductions in solids and nutrient loads, coupled with reductions in bank erosion, are calculated to meet clarity goals at the 1-m depth in the main bay and major eastern embayments. Careful examination of model results at small scales is required to verify large-scale findings, however. We recommend major improvements in monitoring, computation of light attenuation, and in sediment transport modeling to improve the state of the art in modeling and management of water clarity.