Analysis of Temporal Trends of Groundwater Level and Salinity in a Coastal Forested Area in Delmarva Peninsula (VA).

The transition of forests in salt marshes along coastal regions is nowadays well documented. New established environmental conditions linked to both sea level rise and violent storm events threaten the deeply rooted forested area that tend to spatially retreat giving way to new vegetation species finding here their ideal habitat. Freshwater availability, flooding and soil salinity increase can be considered the main drivers of the conversion from forested to salt marsh areas in many of North America coastal regions. In this work, we study groundwater level and salinity data in two points in Delmarva Peninsula (VA), located more or less close to Atlantic shoreline and interpret them on the basis of the relationship among external evapotranspiration, tidal oscillations and rainfall inputs. In correspondence of the chosen points, two wells equipped with CTD-Divers were located collecting data in 2014. These two wells are situated in two different forested areas, the upper one in the regenerative forest, occupied only by mature trees, and the lower one in the persistent forest, occupied only by mature trees, that once dead leave free space for new vegetation species, being unable to recover after storm events. The wells have a similar groundwater level trend, but the lower one is averagely 6 times more saline than the upper one. Groundwater and salinity data of the lower well are analyzed on 1-hour short scale and averaged on a long scale variable from 1 day to 2 months. On short scale groundwater level increases are correlated to cumulative rainfall amounts. Salinity trend is significantly related to groundwater level both on short temporal scale and long temporal scale, and to sea level on some long temporal scales. Based on the results, we try to give a valid explanation about the environmental settling differences between two areas looking at hydrological and geochemical datasets.