Rivers Inflows Impact on Circulation and Biogeochemical behavior of Southern Green Bay, Lake Michigan

Located in the Great Lakes Basin, southern Green Bay is a designated Area of Concern (AOC) due to ecosystem degradation, contaminated sediments, hypoxia, and poor water quality. Restoration of an aquatic system requires a clear understanding of its circulation and thermal regime. Based on assumption that the influence of river loadings is local, most computational studies have not considered the effect of tributaries inflows on hydrodynamics of the bay. This study examines the effect of variability in tributaries inflows and the related lake intrusions on the circulation and thermal regime in lower Green Bay (area south of Chambers Island in Green Bay). Using a state-of-the-art numerical hydrodynamic model, our findings indicate that tributaries inflows influence the circulation and thermal regime, locally near the mouth of the rivers and throughout the bay. Then circulation and thermal regime of the bay is compared for two cases with/without tributary discharges into the bay. Results show that there is less mass exchange and heat flux between lower and upper Green Bay in the hypothetical case of no tributaries inflows. Also, results indicate that the impact is more significant in wet years. This analysis of the simultaneous effects of tributary flows and lake intrusions in the Lake Michigan-Green Bay system can contribute to better understanding the dynamics of the bay and inform future remedial action plans.