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.

August 2018 Groundwater Levels

Eighteen percent, or 5 of 28 USGS observation wells, had groundwater levels within the normal range (25th-75th percentiles) in August. Groundwater levels were above normal at 22 wells (79 percent), including 6 record high August groundwater levels, 10 wells with groundwater levels greater than the 90th percentile, and 6 wells in the 76th-90th percentile range. There was one well with below normal groundwater levels (between the 10th and 24th percentile) in August, and that well was in Wicomico County.



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 groundwater level at observation well WA Bk 25, in Washington County, Maryland was 26.93 feet below land surface, which is an August record high. The previous record was 35.60 feet below land surface in 1996. Normal August groundwater levels at this well range from 44.19 to 47.09 feet below land surface. Monthly record-keeping at this well began in April 1970.

The groundwater level at USGS observation well WI Cg 20, in Wicomico County, Maryland was 7.40 feet below land surface, which is in the below normal range (10th-24th percentiles). Normal groundwater levels for August range between 5.04 and 7.38 feet below land surface. Record-keeping at this well began in August 1949.

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

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