Reports
Ground-water levels and pumpage trends in the major Coastal Plain aquifers of Southern Maryland between 1970 and 1996
2001, Achmad, G. and Hansen, H.J.
Open File Report 2000-02-12
Abstract
This report consists of an assemblage of water-level data and ground-water pumpage data for the Southern Maryland Coastal Plain aquifers located in Anne Arundel, Calvert, St. Mary’s, Prince George’s, and Charles Counties. The aquifers represented are the Patuxent, Lower Patapsco, Upper Patapsco, Magothy, Aquia, and Piney Point-Nanjemoy. The water-level data are summarized in a series of maps showing potentiometric surfaces and water-level changes during a 27-year period beginning in 1970. In addition, hydrographs from selected long-term observation wells and pumpage bar graphs are presented to further document the effects of pumpage on water levels surrounding major well-field sites.
Key findings regarding ground-water level and pumpage trends between 1980 and 1996 follow:
Patuxent Aquifer: Pumpage in Southern Maryland peaked in 1990 (13.27 million gallons per day). By 1996 withdrawals had declined to 7.91 million gallons per day. The aquifer is chiefly used by major appropriators in Anne Arundel County and Prince George’s County. In 1996 water-level drawdowns occurred in the Glen Burnie and Crofton Meadows/Bowie areas forming significant cones-of-depression. A progressively declining potentiometric surface is not apparent in Anne Arundel and Prince George’s Counties because an overall decrease in pumpage has occurred since 1980.
Lower Patapsco Aquifer: This aquifer produces more ground water (about 29.61 million gallons per day in 1996) than any of the other aquifers in Southern Maryland. The aquifer is chiefly used by major appropriators in Anne Arundel County (22.85 million gallons per day in 1996) and in Charles County (5.71 million gallons per day in 1996). The largest water-level declines reported for the Lower Patapsco aquifer between 1985 and 1996 are in the La Plata/Waldorf area of Charles County (75 feet to 97 feet). Over the same time period, water-level declines in Anne Arundel County have been observed at Severndale (40 feet) and Crofton Meadows (67 feet). A decline of 25 feet was recorded at Bowie in adjacent Prince George’s County. Water levels have recovered up to 41 feet in the Glen Burnie area due to discontinued Lower Patapsco pumpage at the Dorsey Road and Sawmill Creek well fields.
Upper Patapsco Aquifer: In 1996 about 8.4 million gallons per day were withdrawn from the Upper Patapsco aquifer in Southern Maryland, probably over half by domestic and other minor users. Usage in 1996 was greatest in Anne Arundel County (5.23 million gallons per day) with lesser withdrawals from the Upper Patapsco aquifer in Prince George’s County (1.1 million gallons per day) and Charles County (2.0 million gallons per day). Nonetheless, 1996 water levels were deepest in Charles County, particularly in the La Plata area (117 feet below sea level), where a decline of about 78 feet has occurred since 1970.
Magothy Aquifer: Reported pumpage from the Magothy aquifer in Southern Maryland in 1996 was 10.35 million gallons per day with about 40 percent assigned to domestic and other minor users. Anne Arundel County accounted for about one-half of the total withdrawal. In Charles County public-supply wells in the Waldorf area are the largest user of the Magothy aquifer (2.4 million gallons per day in 1996). Reported 1980 water levels in the Waldorf area were mostly 30 to 35 feet below sea level. By Fall 1996 water levels had declined to as much as 104 feet below sea level, forming a large cone-of-depression. Magothy water levels observed at the Chalk Point (Potomac Electric Power Company) power plant in southern Prince George’s County were as deep as 66 feet below sea level in 1996, reflecting a decline of 7 to 16 feet since 1980.
Aquia Aquifer: The Aquia aquifer is chiefly used in Anne Arundel, Calvert, and St. Mary’s Counties. Anne Arundel County withdrew 6.39 million gallons per day in 1996 with about 97 percent of the total attributed to widely dispersed domestic wells in the central and southern parts of the county. In 1996 a total of 4.2 million gallons per day was withdrawn in Calvert County with self-supplied domestic wells and other minor users pumping slightly less than half (2.04 million gallons per day). In St. Mary’s County in 1996 Aquia pumpage totaled 5.05 million gallons per day with major appropriators accounting for 3.68 million gallons per day. Fall 1996 water levels were reported to be as deep as 138 feet below sea level in the Lexington Park–Solomons area, where pumpage by major appropriators occurs. Between 1980 and 1996, Aquia water-level in these areas of St. Mary’s and Calvert Counties declined by as much as 70 feet, as cones-of-depression continued to expand and deepen. Elsewhere, reported water-level differences between 1980 and 1996 were less (30 feet to 40 feet in northern Calvert County, 30 feet to 40 feet in eastern Charles County, and 10 feet to 20 feet in southern Anne Arundel County).
Piney Point–Nanjemoy Aquifer: Pumpage from the Piney Point–Nanjemoy aquifer in 1996 was the lowest withdrawal (6.7 million gallons per day) reported for the six major aquifers used in Southern Maryland. Nearly all usage occurs in the southern parts of Calvert and St. Mary’s Counties. In these areas withdrawals are dominated by self-supplied domestic and other minor users. In 1996 major appropriators withdrew only 0.29 million gallons per day (of a total 2.69 million gallons per day) in Calvert County and 0.51 million gallons per day (of a total 3.97 million gallons per day) in St. Mary’s County. Piney Point–Nanjemoy pumpage increased about 3.09 million gallons per day in Calvert and St. Mary’s Counties between 1980 and 1996, causing regional water levels to decline at least 5 to 12 feet based on the few wells available for comparison. Additional wells in Calvert County were added to the network in the Fall of 1999. These water levels ranged between 9 and 50 feet below sea level in central Calvert County and were as much as 18 feet below sea level in the Cove Point–Solomons area. In St. Mary’s County Fall 1998 measurements ranged from 3 feet below sea level near Leonardtown to 37 feet below sea level near California.
