Hydrodynamic and Water Quality Modeling of Ward Cove, Alaska

Ward Cove is a small estuary located on the north side of Tongass Narrows, approximately five miles north of Ketchikan, Alaska. Three activities—pulp mill effluent discharges, log rafting, and seafood processing facility discharges—have introduced contaminants to Ward Cove. A pulp mill began operating in the cove in 1952 and ceased operations in 1997. The bottom of the cove has been covered with fiber mats, sunken logs, and enriched sediments. In addition, the seafood processing and log rafting operations continue discharging. Numerical modeling techniques were developed to simulate the loading of organic material and nutrients, and the resulting response of dissolved oxygen within Ward Cove. A system of models was developed to allow the determination of the circulation and transport within Ward Cove, and the response of critical water quality parameters. The system of models includes the Environmental Fluid Dynamics Code (EFDC) to simulate the circulation and transport of material and the Water Quality Analysis and Simulation Program (WASP) to simulate the response of critical water quality parameters to the loads. The EFDC and WASP models provided a good framework for predicting responses of hydrodynamic and water quality parameters. The results show that the models capture the primary temporal and spatial distribution of temperature, salinity and dissolved oxygen in the system, especially the vertical stratification conditions.