Excess nitrogen from agricultural activity on the Delmarva Peninsula contributes to impairment of Chesapeake Bay. Most of the region's nitrogen load is transported to streams by groundwater. Therefore, quantifying dynamics within the surficial aquifer is necessary for understanding nitrogen loads to the region's streams. We use COMSOL Multiphysics 4.1 to examine heterogeneities within a two-dimensional cross-section of a representative aquifer in order to understand their influence on water-residence times and nutrient transport dynamics.

We found aquifers responded in a predictable manner to the addition of clay heterogeneities. The presence of clay heterogeneities within the aquifer shifts the location of the phreatic divide, which delineates recharge allocation to receiving rivers. Furthermore, hydraulic pressure head increases with the presence of clay strata, shortening residence time of water and nutrients within the aquifer. When water and dissolved nutrients spend less time within the aquifer, a higher percentage of annual nutrient load is released into streams. By understanding how nutrients flow within the aquifer, regulatory and management strategies can be developed to mitigate continued degradation of water resources in the region.