Reports
Land subsidence monitoring to assess potential effects Of groundwater withdrawals from coastal plain aquifers In Maryland: Fall, 2023 Survey
2024, Ulizio, T.P.
Administrative Report 24-02-01
Key Results
A GPS campaign was conducted October 2-6, 2023, to determine heights of nine 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). An additional southern Maryland mark is located at Rosaryville State Park (ROS1), where groundwater use is relatively low. 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 2023 ellipsoid heights determined through OPUS Projects processing of GPS data were 3.598 meters at ARNO, -6.225 meters at BROA, 7.046 meters at CROF, -1.558 meters at COV1, -2.110 meters at LEX1, 28.740 meters at WAL1, -35.677 meters at MSTP, and -36.060 meters at PTNK. Raw GPS data acquired at ROS1 did not meet OPUS Projects data quality thresholds; therefore no GPS data from ROS1 was processed for the 2023 survey. Computed height uncertainties, following the final network adjustment in OPUS Projects, for all marks is +/- 0.1 cm. Uncertainty computed in the latitudinal and longitudinal positions of MGS marks, following the final network adjustment in OPUS Projects, is smaller than could be detected by OPUS Projects. Including these ellipsoid height data from 2023, vertical velocities have been updated for the nine 3d marks. 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 4.4 mm/yr., LEX1 is subsiding at 3.0 mm/yr., and WAL1 is subsiding at 6.7 mm/yr. In the Blackwater National Wildlife Refuge, MSTP is subsiding at 13.2 mm/yr. and PTNK is subsiding at 6.6 mm/yr.
