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Water Science for Maryland, Delaware and the District of Columbia

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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.

January 2018 Groundwater Levels

Thirty-six percent, or 10 USGS observation wells, had groundwater levels within the normal range in January. Groundwater levels were above normal at 3 wells including a record high at well SO Cf 2 in Somerset County, Maryland. Groundwater levels were below normal at the remaining 15 wells, including 10 wells in the 10th-24th percentile range, 3 wells below the 10th percentile, and 2 wells at record lows: USGS Observation wells HO Cd 79 and MO Eh 20. This is the third consecutive month that observation well MO Eh 20 in Montgomery County, Maryland set a new monthly record low. Between December and January, groundwater levels decreased at 12 of 28 wells, and increased at 16 wells.

 

 

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 HO Cd 79, in Howard County, Maryland, was at a record January low at 29.94 feet below land surface. The previous January record low was 29.54 feet below land surface in 1992. Groundwater levels have been below normal for the past 11 months at this well. Normal January groundwater levels at this well range from 25.97 to 29.07 feet below land surface. Monthly record-keeping at this well began in January 1988.

The groundwater level at USGS observation well
SO Cf 2, in Somerset County, Maryland, rose 0.7 feet to a January and all-time record high at -0.11 feet below land surface, which because it is a negative number is above land surface in the well casing. The previous January record high was in 1964 at 0.46 feet below land surface. The previous all-time record was 0.20 feet below land surface in October 2009. The normal range of groundwater levels for January at this well is between 0.85 and 1.45 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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