Characterization of groundwater and surface water geochemistry in an agricultural setting at EKU Meadowbrook Farm, Madison County, Kentucky

Agricultural activities often contaminate watersheds with excess nutrients leading to poor water quality and eutrophication. Eastern Kentucky University (EKU) Meadowbrook Farm raises crops and livestock, which contribute dissolved nutrients to the neighboring Muddy Creek watershed. Our goal is to understand Farm water geochemistry to develop methods to sequester phosphorous and limit nutrient contamination. During the Cindy storm event, concentration of Ca2+, Mg2+, and Na+ within baseline source waters decreased with increasing discharge through the weir. This behavior represents dilution of Farm groundwater by storm precipitation. However, K+ spiked concurrently with increased discharge then progressively decreased over the duration of the storm, suggesting that K+ was flushed from soil by rain waters. Nutrient concentrations generally increase with increased discharge indicating transport by surface runoff. PO43- closely tracks discharge, suggesting PO43- transport from the surficial soil substrate via flushing by precipitation. NO3- exhibited nearly identical transport behavior as K+, however NO3- levels reached a higher baseline concentration than pre-storm levels. This suggests infiltration and retention of NO3- within soil and groundwater during fair weather, initial flushing during the rain event, and then prolonged NO3- release from Farm soil and groundwater. NH4+ immediately increases with the first rainfall then decreases to levels slightly above background. This behavior suggests rapid release of NH4+ from soil followed by accumulation within the weir pool and then subsequent flushing during the precipitation event