Reports
The water resources of Allegany and Washington Counties
1962, Slaughter, T.H. and Darling, J.M.
Bulletin 24
Abstract
Allegany and Washington Counties have a combined area of 883 square miles and had a population of approximately 175,000 in 1960. The area includes a small part of the Blue Ridge physiographic province, all of the Ridge and Valley province, and part of the Appalachian Plateau province.
The area is underlain by rocks ranging in age from granitic gneiss, metabasalt, and metamorphosed shale and sandstone of the Precambrian and Cambrian systems through limestone, shale, and sandstone of the younger rock systems of Paleozoic age. Thin surficial deposits of the Quaternary and Recent systems are present along the Potomac River and its tributaries. All of the formations are aquifers, at least locally.
The area has been subdivided into seven ground-water provinces (or water provinces) on the basis of differences in physiography and geology. They are from east to west: (1) South Mountain-Elk Ridge, (2) Hagerstown Valley, (3) Hancock-Indian Springs, (4) Warrior-Evitts Mountains, (5) Sideling Hill-Town Creek, (6) Cumberland, and (7) Georges Creek basin.
The area has a humid, temperate climate. The mean annual temperature is 53°F and the mean annual precipitation is about 40 inches.
The average daily use of ground water from wells and springs in 1959 was estimated to have been about 7.2 mgd (million gallons per day), which is less than 2 percent of the ultimate quantity, about 400 mgd, estimated to be available on a sustained basis.
The best aquifers are the limestones of the Hagerstown Valley, where locally wells yield as much as 400 gpm. In other sections sandstone yields as much as 200 gpm and shale as much as 50 gpm to wells. Not everywhere are the rocks good aquifers. In a few places even domestic ground-water supplies are difficult to obtain.
Periodic measurements of water-level fluctuations in observation wells since 1947 have indicated no general declining or rising trend in water levels. As of 1960, no known water-supply problems exist as a result of heavy pumping from aquifers.
The chemical quality of the water is variable but is generally suitable for most purposes. In the areas underlain by limestone the hardness of the water ranges from 12 to 730 ppm. This water is considered "hard". Locally, the iron content of the water is sufficiently high to necessitate treatment. In the Cumberland and Georges Creek basin water provinces, water containing more than 200 ppm of chloride occurs in some wells deeper than 500 feet. At places in the Georges Creek Basin, the pH of the ground water is less than 6.0 and the sulfate and iron contents are high, 455 ppm and 6.5 ppm, respectively, as a result of mine drainage.
The mean temperature of water from shallow sources approximates the mean annual atmospheric temperature of 53°F. Temperature logs of deep wells indicate that the water near the surface is warmer in the western part of the area, than it is in the eastern part. Temperature logs of deep wells indicate that the reciprocal geothermal gradients to depths of about 5OO feet range from about 106 feet to 353 feet per °F.
