Prettyboy Reservoir occupies 206.5 sq/km of northern Baltimore County, Maryland, also known as the Hereford Zone. Even though the reservoir is located in the county, the City of Baltimore owns the reservoir and the surrounding land of forested watershed. The reservoir is one of three reservoirs created to supply the Metropolitan Baltimore municipal water system for Baltimore City, Baltimore County and northern Anne Arundel County constructed by the Baltimore City Department of Public Works. Prettyboy Reservoir, along with Loch Raven Reservoir that is downstream on the Gunpowder Falls, provide about 61% of the drinking water for the entire Baltimore Metropolitan system. For this reason, the Prettyboy is considered a “source water” or drinking water watershed.