Maryland Department of Natural Resources

Charles County Observation-Well Network

Project Details

The Charles County water-level network is one of three county observation-well networks maintained by MGS and funded through county cooperative agreements. Other counties include Anne Arundel and Queen Anne’s counties.

The primary objective of these networks is to monitor the effects of water-supply withdrawals on groundwater levels at both a local (well field) and regional scale. More specifically the water-level data are used to help assess (1) long-term sustainability of the water supply; (2) well interference (drawdown at each well in a multiple-well system added to drawdowns at the other wells); (3) potential for increased development of the aquifers; (4) potential for salt-water intrusion, where applicable; and (5) the role of ground-water extraction in land subsidence.

The Charles County observation-well network, initiated in 1999, is currently funded through a cooperative agreement between Maryland Geological Survey and Charles County Department of Planning and Growth Management. The network currently consists of 28 wells located mainly in the central and northern part of the County. Aquifers monitored include the Patuxent (14 wells), Lower Patapsco (8 wells), Upper Patapsco (4 wells), and Magothy (2 wells). Frequency of measurement ranges from 6 times a year to semiannual (spring and fall). Groundwater withdrawals are also correlated with continuous water levels in 8 observation wells located in the Waldorf area (Magothy, Upper Patapsco, Lower Patapsco, and Patuxent aquifers) and in the Indian Head/Bryans Road area (Lower Patapsco and Patuxent aquifer systems). Pumpage data were obtained from Charles County Department of Public Utilities. Generally, for all aquifers, increased pumpage occurs during summer and fall, causing water levels to decline while decreased pumpage occurs during winter and spring, causing a deceleration of declines.



Current Water Level Trends

Magothy aquifer


Water levels in the Magothy aquifer fluctuate with usage but the overall trend shows continuing gradual declines. The largest fluctuations, up to 60 feet, occurred at St. Charles (CH Bf 133) (fig. 4). Water levels range from 67.98 ft below sea level at Sun Valley (CH Be 43) to 134.48 ft below sea level at St. Charles (CH Bf 133). Recent pumpage in the Waldorf area ranged from 2.49 million gallons per day (Nov 2024) to 3.31 million gallons per day (July 2024).

Upper Patapsco aquifer


Water levels in the Upper Patapsco aquifer system fluctuate as much as 9 feet in response to pumping and have continued to decline slightly or hold steady in recent years. Water levels range from 16.64 ft below sea level at Douglas Point (CH Da 21) to 83.48 ft below sea level at St. Charles (CH Bf 157).

Lower Patapsco aquifer


Water levels in the Lower Patapsco aquifer system fluctuate seasonally due to usage but have exhibited flat or recovering trends in the past few years. Fluctuations due to pumping are especially apparent in the La Plata area (CH Ce 56) where water levels varied as much as 27 feet, and St. Charles (CH Bf 146) where they were almost 11 feet. Water levels in the Lower Patapsco system range from 18.25 ft below sea level at Douglas Point (CH Da 20) to 173.06 ft below sea level at La Plata (CH Ce 56). Recent pumpage in the Waldorf area ranged from 1.28 million gallons per day (Dec 2024) to 2.94 million gallons per day (June 2025).

Patuxent aquifer


Water levels in the Patuxent aquifer system have continued to decline within the past year. In western Charles County, water levels at Chapmans Landing, Bryans Road and Mattawoman Water Treatment Plant (CH Bc 75, CH Bc 77, CH Bc 78 and CH Cc 34) continue to decline at rates of up to approximately 5 ft/yr. Water levels in the Patuxent aquifer system range from 14.89 ft below sea level in the western part of the county at Douglas Point (CH Da 18) to 126.6 ft below sea level at Chapman’s Landing (CH Bc 75). Recent pumpage in the Bryans Road area ranged from 462,227 gallons per day (Nov 2024) to 549,677 gallons per day (July 2024).