Reports
Land subsidence monitoring to assess potential effects of groundwater withdrawals from coastal plain aquifers In Maryland: Fall, 2024 Survey
2025, Ulizio, T.P.
Administrative Report 25-02-01
Key Results
A GPS campaign was conducted October 27, 2024 to November 4, 2024 to determine heights of eight 3d marks to assess the potential effect of groundwater withdrawals from aquifers in the Coastal Plain of Maryland. Three marks are located at major well fields in Anne Arundel County, Maryland, at the Arnold Water Treatment Plant (ARNO), the Broad Creek Water Treatment Plant (BROA), and the Crofton Meadows Water Treatment Plant (CROF). Three marks are located at or near major well fields in southern Maryland, at Cove Point State Park (COV1), Lexington Park (LEX1), and Waldorf (WAL1). Two marks are located on the Eastern Shore of Maryland in the Blackwater National Wildlife Refuge in Dorchester County, at Money Stump (MSTP) and Peter’s Neck (PTNK). The marks at the Blackwater National Wildlife Refuge are located in low-lying areas near the shoreline of the Chesapeake Bay where inundation, caused by relative sea-level rise, makes assessing the role of land subsidence all the more critical. The GPS data were processed using the National Geodetic Survey’s Online Positioning User Service (OPUS) Projects (5.2) utility in the International Terrestrial Reference System of 2014. The 2024 ellipsoid heights determined through OPUS Projects processing of GPS data were 3.599 meters at ARNO, -6.227 meters at BROA, 7.050 meters at CROF, -1.559 meters at COV1, -2.110 meters at LEX1, 28.730 meters at WAL1, -35.679 meters at MSTP, and -36.076 meters at PTNK. GPS data were not acquired at Rosaryville State Park (ROS1) due to previous survey data from the site not meeting OPUS Projects data quality thresholds and the continued obstruction of satellite visibility by vegetation. Following the final network adjustment in OPUS Projects, computed height uncertainty is +/- 0.1 cm, and computed uncertainty for the latitudinal and longitudinal positions is smaller than could be detected by OPUS Projects at all MGS marks. Vertical velocities have been updated for the eight 3d marks using ellipsoid height data from 2024. In Anne Arundel County, ARNO is subsiding at 3.1 mm/yr, BROA is subsiding at 2.5 mm/yr, and CROF is subsiding at 2.6 mm/yr In southern Maryland, COV1 is subsiding at 4.9 mm/yr, LEX1 is subsiding at 3.3 mm/yr, and WAL1 is subsiding at 6.7 mm/yr In the Blackwater National Wildlife Refuge, MSTP is subsiding at 10.6 mm/yr and PTNK is subsiding at 8.4 mm/yr.
