Forecast of Summer Anoxia in the Chesapeake Bay

This paper presents a forecast model to predict summer anoxia in the Chesapeake Bay using preceding spring information of nitrogen and phosphorus loads, water temperature, algae concentration, and freshwater flows. It's based on a regression of over 20 years of observed data. The use of anoxic intensity, a DO-normalized anoxic volume, versus the traditional anoxic volume as the forecasting estimator is described. Anoxic volume can be influenced by partial mixing or other factors that sometimes causes a higher anoxic volume but with actually less intensity in the anoxic condition. This paper recommends using quadratic terms of separate nitrogen and phosphorus loads, and other conditions such as freshwater flows from the upper Bay and water temperature, as regressors. More than 18 regression equations with different combinations of explanatory variables were compared, and the importance of their effects on the anoxia forecast is discussed.