Background

The Maryland Geological Survey is currently monitoring a network of domestic wells and observation wells on Kent Island in Queen Anne’s County, Maryland. The purpose of the monitoring program is to determine trends in chloride concentrations and specific conductivities in groundwater from the Aquia aquifer associated with brackish-water intrusion from the Chesapeake Bay. Drummond (1988) described brackish-water intrusion on Kent Island, and included discussions of distribution, source, and changes with time of brackish water.

A monitoring network was established in 1986 based on wells sampled in Drummond (1988) and was sampled annually until 2013, biennially from 2013 to 2017, and is currently being sampled every 5 years. The report linked on this page presents data from the monitoring program.

Key Results

Maps showing well locations are found on figures 1 and 2 of Administrative Report 23-02-02. The maps also show zones of generalized trends in chloride concentrations of water from network wells. Most trends in chloride concentrations reported in recent years continued through 2022. Chloride concentrations in some wells in the Bay City/Matapeake Estates areas continue to show an overall increase. Changes in chloride concentrations were generally not seen in samples from the lower Aquia aquifer, where salinities are much higher and screened intervals are farther below the freshwater/ brackish-water interface. An exception to this is well QA Eb 156, which has shown a general increase in chloride since 1998.

The monitoring data indicate that, in general, chloride concentrations are elevated and increasing in the upper Aquia aquifer in the central part of the bay shore on Kent Island; north and south of that central area along the bay shore, chloride concentrations are elevated but do not show a general trend. The lower Aquia aquifer is brackish along the entire bay shore. Inland from the bay shore (about ¼ mile) the entire section of the Aquia is fresh, and does not show evidence of an increasing trend. Increasing trends in chloride concentrations may indicate slight landward movement of the brackish-water interface, but variations mask the trends on parts of Kent Island. The possible explanations given by Drummond (2001) for data through 1999 are still plausible for data through 2022.

References

Drummond, David D., 1988, Hydrogeology, brackish-water occurrence, and simulation of flow and brackish-water movement in the Aquia aquifer in the Kent Island Area, Maryland: Maryland Geological Survey Report of Investigations No. 51, 131 p.

Drummond, David D., 2001, Hydrogeology of the Coastal Plain Aquifer System in Queen Anne’s and Talbot Counties, Maryland, with emphasis on water-supply potential and brackish-water intrusion in the Aquia aquifer: Maryland Geological Survey Report of Investigations No. 72, 141 p.