Charles County Observation-Well Network

The Charles County water-level network is one of five observation-well networks maintained by MGS and funded through cooperative agreements with Anne Arundel, Calvert, Charles, Queen Anne’s, and St. Mary’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 29 wells located mainly in the central and northern part of the County. Aquifers monitored include the Patuxent (13 wells), Lower Patapsco (8 wells), Upper Patapsco (5 wells), and Magothy (3 wells). Frequency of measurement ranges from 6 times a year to semiannual (spring and fall).







Current Water Level Trends

Magothy aquifer


Water levels in the Magothy aquifer continue to fluctuate in response to pumpage, but generally show slightly declining or flat trend. Water levels range from about 68.04 ft below sea level at Sun Valley (CH Be 43) to about 117.81 ft below sea level at St. Charles (CH Bf 133). The observation well at John Hanson Middle School (CH Bf 134) developed a leak in the casing and will be dropped from the network and abandoned.

Upper Patapsco aquifer


Water levels in the Upper Patapsco aquifer have shown a relatively flat trend, except for water levels at St. Charles (CH Bf 157) which continue to decline. Water levels range from 15.28 ft below sea level at Douglas Point (CH Da 21) to 82.15 ft below sea level at St. Charles (CH Bf 157). A monitoring well at St. Charles (CH Bf 151) was abandoned in July 2017 to address a damaged and leaking well casing.

hydrograph for observation well CH Da 20 in the Lower Patapsco aquifer

Lower Patapsco aquifer


Water levels in the Lower Patapsco aquifer in wells in the far northern and northwestern parts of the county (CH Be 72, CH Bc 24, CH Bc 81, and CH Cc 31) have recovered by as much as 30 feet since late 2007, and have either continued to recover or have held steady since 2012. These recoveries, beginning in 2008, resulted from a drop in usage of the Lower Patapsco aquifer system in the western part of the County when the new Patuxent aquifer system wells were added to the system. Lower Patapsco water levels at St. Charles (CH Bf 146), La Plata (CH Ce 56), Chapel Point Woods (CH De 52) and Douglas Point (CH Da 20) show a generally flat trend. Waterlevels in the Lower Patapsco aquifer range from about 16.8 ft below sea level at Douglas Point (CH Da 20) to 138.51 ft below sea level at La Plata (CH Ce 56).

hydrograph for observation well CH Bc 77 in the Patuxent aquifer

Patuxent aquifer


Water levels in the Patuxent aquifer continue to decline or exhibit a flat trend. In the northeastern part of the County at Malcom (CH Bg 18), these declines have slowed in recent years. Elsewhere in the County, water levels in the Patuxent aquifer are declining at rates of approximately 1 to 4 ft per year with the fastest declines occurring in the Chapmans Landing/Bryans Road area wells (CH Bc 75, 77 and 78). Water levels in the Patuxent aquifer range from 12.84 ft below sea level in the western part of the county at Douglas Point (CH Da 18) to 102.6 ft below sea level at Chapman’s Landing (CH Bc 77). Measurements from the production well at Bryans Road (CH Bc 78) are conspicuously flat from 2015 to 2018, caused by a blockage in the measuring tube.