Filling in the Gaps : Modeling the Role of Groundwater in Lake Erie’s Nutrient Budget

Lake Erie is a hotspot for large harmful algal blooms, which damage human health, degrade natural habitats, and impair industries reliant on the lake. The Maumee River watershed, the largest in the Great Lakes, often acts as a major driver for these blooms, as it is the largest contributor of nutrients to the lake, mainly attributed to intense agricultural activity. Consequently, surficial transport of phosphorus and nitrogen within the Maumee River watershed has been extensively studied. However, there has been very little research into the role of groundwater here, especially groundwater modeling studies. Here, I evaluate the literature that has explored nutrient transport to Lake Erie, with a focus on the Maumee River watershed, and examine groundwater nutrient transport. This knowledge will inform nutrient management decisions, especially those regarding future and legacy nutrient loads. In Chapter 1, I review the current state of literature on hydrologic nutrient modeling in the Lake Erie Basin. I highlight common themes in the literature and detail prominent gaps. Specifically, I focus on the role of groundwater in nutrient modeling studies within the Maumee River watershed and recommend future directions for research. In Chapter 2, I create a spatially explicit, process-based groundwater model of the Maumee River watershed. This model allows me to quantify the contributions of groundwater in the context of total basin loading. I then quantify the role of legacy nutrient accumulation by reducing input loads in a projected future scenario. This research completes the nutrient budget by highlighting ‘hidden’ groundwater nutrient loads and informs the timescale of subsurface nutrient management.