Instrumentation of a Natural Terrestrial Site to Assess Seasonal Variations in Temperature, Water Level, Pore Pressure, and Salinity

Climate change and sea level rise have the potential to significantly alter existing natural groundwater levels and pore water chemistry in soil deposits that are near the ocean. As ocean levels rise, a salinity front advances through the groundwater, and extreme events such as hurricanes or winter storms cause the introduction of saline water further inland at the surface. After a high-water event, standing surface water left in pools evaporates, leading to high-salinity water pools or salt deposits at the surface. Existing animal burrows, desiccation cracking, and plant root structures (for plants that are alive or dead) facilitate the exchange of salts and other contaminants in a complex regime. The current study describes the process of instrumentation of a natural terrestrial site to monitor seasonal variations in temperature in the soil profile, fluctuations in groundwater level, changes in soil pore pressure, and changes in soil salinity. The goal of this instrumentation program is to develop a more specific understanding of the effect of changes in salinity due to flooding and sea level rise on the physical, chemical, mechanical, and biological properties of soils. For this study, a project site was selected at the St. Jones Reserve, located along the St. Jones River and the Delaware Bay in the state of Delaware, in the USA. The site is located south of the Dover Air Force Base and is part of a roughly 700-acre sanctuary, which includes the Delaware National Estuarine Research Reserve, and the St. Jones Center for Estuarine Studies. In the field at the site, a series of instruments and data logging systems were installed along a transect that follows a salinity gradient from non-saline to saline pore water. This site has been heavily instrumented with various instruments by the current team as well as other researchers, to assess seasonal variations in temperature, pore pressure, volumetric water content, and salinity. This study will provide preliminary data from the initial monitoring stages, along with background knowledge in regard to sensor selection, fabrication of sensor arrays, and installation procedures of the data logging system for this site.