SOIL SALINITY AND WATER LEVEL CONDITIONS IN AGRICULTURAL FIELDS OF EASTERN NORTH CAROLINA - MODELING THE IMPACT OF EXTREME EVENTS

Many regions in the eastern United States are experiencing saltwater intrusion and soil salinization issues. In coastal North Carolina, soil salinization is affecting productivity in agricultural fields that are drained by numerous and extensive networks of drainage ditches and canals. In this study, we installed soil moisture sensors and groundwater monitoring wells in several agricultural fields to monitor soil salinity and groundwater levels over a multi-year period. We then used the software package DRAINMOD-S to assess how extreme events (i.e., hurricanes and droughts) affect soil salinity and water level conditions at the field sites. Calibration results indicate that DRAINMOD-S was effective in simulating observed seasonal and annual variations in soil salinity and water level conditions, with model outputs closely matching field data. Results from scenario modeling reveal that surges in salinity and water levels after hurricane events are short lived, with environmental variables returning to pre-hurricane levels shortly after cessation of storm events. In contrast, simulated drought events lead to declines in both groundwater and soil salinity levels during the events. However, following the events, these levels quickly rebound to background levels. These results suggest that although soil salinity and water levels are highly sensitive to extreme events, these systems are surprisingly quite efficient in returning to background levels under current environmental conditions. The outcomes from this study may therefore be useful in deriving a better understanding of how soil salinity and water levels respond to environmental drivers and what management decisions may be employed to manage the conditions.