Groundwater Use

Groundwater is an important source of fresh water in Maryland. Out of a total population of about 6 million people, approximately 2.3 million rely on groundwater for their drinking water supply (with the remainder supplied by surface water)(Dieter and others, 2018). Groundwater is nearly the sole source of drinking water in Maryland's coastal plain (area east of I-95). Approximately 1.4 million people rely on groundwater in the coastal plain. In 2015, the population in Maryland served by groundwater was 906,695 (19.8%), and that served by surface water was 3,675,758 (80.2%). While groundwater is not used as much as surface water as a water source, some towns and most domestic users in central and western Maryland also rely heavily on groundwater. Four out of every 10 Marylanders rely on groundwater sources for domestic water, with one out of 10 using an individual well. Aside from being a crucial drinking water source, groundwater is also important for irrigation, commercial and industrial uses, and power plants (thermoelectric).

In 2015, the primary use of groundwater in Maryland was domestic (self-supplied) followed by public supply and irrigation. Industrial, mining, livestock watering, aquaculture, and thermoelectric use (power plants) accounted for relatively smaller withdrawal amounts.
[Data from Dieter et al, 2018, Estimated use of water in the United States in 2015: U.S. Geological Survey Circular 1441, Online Report here]

Maryland Department of the Environment (MDE), as the trustee of the state water resources, has the responsibility of controlling the impacts of groundwater withdrawal through the Water Appropriations and Use Permit process. Through the permit review process, the MDE Water Supply Program (WSP) works to ensure that groundwater withdrawals do not exceed the sustained yield of the state's aquifers. The permitting process also ensures that public drinking water systems obtain the best possible source of water in regard to quality and sustainability.

As of December 2021, WSP manages approximately 6,900 Water Appropriation and Use Permits, with about 6,000 of these being specifically for groundwater withdrawals. Large permits are defined as those above 10,000 gallons per day (gpd), average use. There are about 1,500 large groundwater permits for agricultural water use and 1,000 large groundwater permits are for non-agricultural water use.

More information

MDE Groundwater Protection Program Report to the Maryland General Assembly, Dec. 2021 (pdf, 1 MB)
USGS Estimated use of water in the United States in 2015 (pdf, 42 MB)