Land subsidence monitoring to assess potential effects of groundwater withdrawals from coastal plain a quifers in Maryland: Fall, 2017 survey
2018, Andreasen, D.C.
Administrative Report 18-02-03
A GPS campaign was conducted October 16-20, 2017 to determine the heights of seven 3d marks to assess the potential effects of groundwater withdrawals from Maryland’s coastal plain aquifers. The marks are located at major well fields in Anne Arundel County, Maryland, at Arnold (mark ARNO-1), Broad Creek (mark BROA-1), and Crofton Meadows (mark CROF-1), and at or near major well fields in southern Maryland at Cove Point (mark COV-1), Lexington Park (mark LEX-1), and Waldorf (mark WAL-1). One mark at Rosaryville State Park (mark ROS-1) in southern Maryland is located in an area of relatively low groundwater use. The GPS data were processed using the National Geodetic Survey’s Online Positioning User Service (OPUS) Projects utility. The ellipsoid heights determined through OPUS Projects were 3.644 meters at ARNO-1, -6.182 meters at BROA- 1, 7.085 meters at CROF-1, -1.508 meters at COV-1, -2.088 meters at LEX-1, 33.834 meters at ROS-1, and 28.797 meters at WAL-1. Height uncertainty for the measurements as reported by OPUS Projects is approximately +/- 0.1 centimeter for all marks with the exception of WAL-1 which had a reported uncertainty of +/- 0.2 centimeters. The greater uncertainty for that mark is possibly attributed to a shorter occupation time. Ellipsoid heights at ARNO-1, BROA-1 and CROF-1 show a slight decline over the period of record, however, the error associated with the heights (reported at +/- 0.1 cm by OPUS Projects for the 2017 values) and fairly significant scatter in the data makes identifying a clear trend difficult. No trends are discernable for the marks in southern Maryland since GPS readings only started in 2016.