USGS - science for a changing world

Water Science for Maryland, Delaware and the District of Columbia

Groundwater Levels

The USGS monitors groundwater levels in surficial or unconfined aquifers, providing observations that can be compared to both short-term and long-term changes in weather conditions. The groundwater wells used for the monthly water summary were selected based on the following criteria:

  • Located in a surficial or unconfined (water-table) aquifers
  • Open to a single, known hydrogeologic unit/aquifer
  • Groundwater hydrograph generally reflects response to weather
  • No indicated nearby pumpage and likely to remain uninfluenced by pumpage or changes related to human activities
  • Minimum period of record is 10 years of continuous/monthly records
  • Minimally affected by irrigation, canals, drains, pipelines, and other potential sources of artificial recharge
  • Well has casing – dug wells are generally not used
  • Water levels show no apparent hydrologic connection to nearby streams
  • Well has never gone dry
  • Long-term accessibility likely, such as on public land

In the Maryland, Delaware, and District of Columbia region, it is useful to compare current data to historical data, such as data from the droughts of 2002 and the 1960s. There are 11 wells that have over 60 years of groundwater data, and 23 wells have more than 30 years of groundwater data as of 2017.

March 2019 Groundwater Levels

Groundwater levels were at record March highs at 8 of 28 wells, above the 90th percentile at 9 wells, within the 76th-90th percentile range at 5 wells, and in the normal range (between the 25th and 75th percentiles) at 5 wells, and below normal at the observation well in Garrett County. Between February and March, groundwater levels increased at 15 wells and decreased at 13 wells included in this report.



Click here to access the clickable groundwater map.

In the 5-year hydrographs for the selected wells, groundwater levels are shown as a dark blue line. Each monthly measurement is colored according to the percentile rank compared to the historical values at the site for the month. The normal range is displayed as a white band and is based on the period of record. The maximum water level is at the top of the upper blue section, and the minimum water level is at the bottom of the lower blue area in the graph. The two wells in Harford County that set all-time record highs are featured below.


The groundwater level at observation well BA Ea 18, in Baltimore County, Maryland, was 10.00 feet below land surface, which is a March record high and an all-time record high. The previous March record was 15.62 feet below land surface in 1997. The groundwater level rose almost 4 feet between February and March. The March 2019 value also was the all-time record high for this well, exceeding the all-time record high set in January 2019, and reaching the highest level since data collection began in 1956. Groundwater levels at this well have been at record highs for the last 6 consecutive months.

The groundwater level at USGS observation well GA Bc 1, in Garrett County, Maryland, was 12.16 feet below land surface, which is below normal. This was the only observation well out of 28 that was below normal.

Click here to view five-year groundwater hydrographs for other wells.

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