Surface Water-Groundwater Connections as Pathways for Inland Salinization of Coastal Aquifers
Coastal agricultural zones are experiencing salinization due to accelerating rates of sea-level rise, causing reduction in crop yields and abandonment of farmland. Understanding mechanisms and drivers of this seawater intrusion (SWI) is key to mitigating its effects and predicting future vulnerability of groundwater resources to salinization. We implemented a monitoring network of pressure and specific conductivity (SC) sensors in wells and surface waters to target marsh-adjacent agricultural areas in greater Dover, Delaware. Recorded water levels and SC over a period of three years show that the mechanisms and timescales of SWI are controlled by local hydrology, geomorphology, and geology. Monitored wells did not indicate widespread salinization of deep groundwater in the surficial aquifer. However, monitored surface water bodies and shallow (<4 m deep) wells did show SC fluctuations due to tides and storm events, in one case leading to salinization of deeper (18 m deep) groundwater. Seasonal peaks in SC occurred during late summer months. Seasonal and interannual variation of SC was also influenced by relative sea level. The data collected in this study data highlight the mechanisms by which surface water-groundwater connections lead to salinization of aquifers inland, before SWI is detected in deeper groundwater nearer the coastline. Sharing of our data with stakeholders has led to the implementation of SWI mitigation efforts, illustrating the importance of strategic monitoring and stakeholder engagement to support coastal resilience.
This is the peer reviewed version of the following article: Hingst, M.C., McQuiggan, R.W., Peters, C.N., He, C., Andres, A.S. and Michael, H.A. (2023), Surface Water-Groundwater Connections as Pathways for Inland Salinization of Coastal Aquifers. Groundwater. https://doi.org/10.1111/gwat.13274, which has been published in final form at https://doi.org/10.1111/gwat.13274. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited. This article will be embargoed until 11/17/2023.
salinization, saltwater intrusion, coastal groundwater, tidal streams, agriculture, irrigation
Hingst, M.C., McQuiggan, R.W., Peters, C.N., He, C., Andres, A.S. and Michael, H.A. (2023), Surface Water-Groundwater Connections as Pathways for Inland Salinization of Coastal Aquifers. Groundwater. https://doi.org/10.1111/gwat.13274