Collaborative Research: Impact of evaporation and waves on groundwater dynamics in tidally influenced beaches

Beaches are an important part of the coastal zone where fresh groundwater flowing to the sea mixes with salty groundwater that infiltrates from tide and wave action. The biogeochemical reactions in this zone greatly impact beach ecology and determine the contribution of nutrients and contaminants to the coastal ocean. Salinity of the water is an important factor in these reactions, so understanding the distribution of salt is critical. It is typically assumed that the maximum salinity in the groundwater is equal to that of seawater. However, concentrations 3-6 times that of seawater have been observed. Evaporation interacting with waves may be an important mechanism that could change both salinity distributions and groundwater flowpaths, due to the influence of salt concentration on fluid density. The research will provide an intensive field and laboratory experience for two graduate students and undergraduates from diverse backgrounds who will be recruited in collaboration with the Educational Opportunity Program that serves under-represented minority students at New Jersey Institute of Technology. The project will provide a unique learning experience for students. This research will generate new understanding in three primary areas. (1) Model development and upscaling will build on recent advances in modeling evaporation and wave dynamics in beach aquifers by combining these processes to account for water, vapor, and heat transport in the porous medium coupled to subsurface hydrodynamics that incorporate wave action. (2) Data collection will include a set of detailed measurements of beach salinity and hydrodynamics at three field sites in Delaware to better understand these coupled effects in real systems. (3) Site-specific and sensitivity analyses will generate new understanding of the primary controls on evaporation-induced salinity dynamics and the resulting effects on flow physics in intertidal mixing zones. By extending analysis over a range of climatic, hydrogeological, and oceanic conditions, results will capture the range of effects and pinpoint conditions under which it is most important to consider these processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.