146-7 Monitoring Groundwater Levels and Nutrient Fluxes in the Surficial Aquifer Along the Pennsylvania Coastline of Lake Erie

Session: Contaminants Near Groundwater-Surface Water Interfaces (Posters)

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Groundwater discharge along the Pennsylvania shoreline of Lake Erie may contribute to nutrient enrichment and coastal bluff erosion, yet the groundwater dynamics in the region are poorly understood. While nutrient pollution from agriculture has been widely linked to harmful algal blooms, most studies have focused on surface water pathways, leaving a critical gap in knowledge regarding subsurface contributions. This study addresses that gap by investigating the spatial and temporal dynamics of groundwater levels and nitrate concentrations in a coastal agricultural setting. Along the Lake Erie shoreline, highly permeable sands and gravels and low topographic slopes promote high rates of infiltration, and groundwater from the surficial aquifer discharges through the bluff face directly into the lake. In Oct 2024, a monitoring network of six wells with 5 ft screens ~30 ft below ground level was installed in the surficial aquifer at Lake Erie Regional Grape Research and Extension Center, an active grape farm ~ 300 m inland from the Lake. Two piezometers were placed adjacent to wells to enable groundwater sampling near the water table. A bluff-face piezometer and three bluff spring sampling sites were accessed to measure nitrate concentrations in discharging groundwater. Each well is equipped with a conductivity-depth-temperature sensor recording at 15-minute intervals. These data were integrated with meteorological data and fertilizer application records to analyze water level and nutrient concentration trends. Water samples were collected at all sites before and after fertilizer application to establish baseline conditions and assess potential enrichment. The groundwater level for some wells shows a gradual increase over time, while others exhibit high, stable levels. In contrast, a few wells display abrupt changes and irregular fluctuations. Preliminary analysis reveals varied nutrient trends across wells during spring. Some wells exhibited elevated concentrations immediately after fertilizer application, while others declined or remained stable. Notably, the wells closest to the lake consistently recorded the highest concentrations. Subsurface heterogeneity from historic shorelines likely contributes to observed variability. Ongoing work includes seasonal water sampling to quantify interannual variability in nutrients and groundwater levels. Regional climate variables are also being integrated to assess their influence. These findings will inform a variably saturated groundwater flow and solute transport model using FEFLOW, with implications for shoreline stability, water quality, and sustainable land use in coastal agricultural systems.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8391

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