Pennsylvania Geological Survey, 4th Series, Water Resources Report 64 "Groundwater resources in and near the anthracite basins of Schuylkill and adjacent counties, Pennsylvania" by Becher, A.E.       Groundwater from the Mauch Chunk Formation is an essential potable water resource for communities in and adjacent to the Southern and Western Middle Anthracite fields because much of the groundwater and surface water that discharges from the coal-bearing Llewellyn and Pottsville Formations contains excessive quantities of iron, manganese, and acidity. Only reservoirs and headwater streams in upland areas are suitable for surface-water supply. Fifty-two percent of the average 51 million gallons per day of water used in 1981 was withdrawn by public suppliers; 67 percent of this water came from surface sources. Severe water shortages were experienced by 21 of 31 public suppliers during a drought in the period 1980-81. Groundwater contributions (base flow) sustain the flow of East Mahantango Creek, Shamokin Creek, and the Schuylkill River during years of below-normal precipitation when winter-spring recharge is near or above normal. Average daily base flows of East Mahantango Creek and Shamokin Creek are 370 and 580 gallons per minute per square mile of drainage area, respectively; these flows represent groundwater discharges from the Mauch Creek and Llewellyn Formations, respectively.       Four potential aquifers are readily accessible to communities in and near the anthracite fields of the Ridge and Valley physiographic province. The Pocono and Pottsville Formations are composed of conglomerate and sandstone. These rocks form high, sinuous ridges adjacent to long valleys underlain by the sandstone, siltstone, and shale of the Mauch Chunk and Llewellyn Formation. Groundwater-flow systems in these rocks grade literally from confined to unconfined and range in area from less than one to tens of square miles.       Some layered flow systems may not be connected vertically except through boreholes. The natural flows of systems in the Llewellyn Formation have been changed greatly by underground mining. High-yield flowing wells have been developed in confined systems of the Mauch Chunk Formation near the nose of plunging synclines and in the Pottsville where the land surface and rock layers slope in the same direction.       Wells in the Pocono and Llewellyn Formations yield only small supplies of water (15 to 20 gallons per minute). One of every two wells drilled for maximum yield in either the Mauch Chunk or Pottsville Formation yields in excess of 75 gallons per minute. Maximum yields of single wells in the Mauch Chunk and Pottsville Formations are 800 and 400 gallons per minute, respectively.       A specific yield of 0.034 was calculated for the zone of water-table fluctuation in a 1- square-mile groundwater basin draining the Mauch Chunk Formation. Large-production wells in the Pottsville or Mauch Chunk Formation spaced less than 1,500 feet apart along strike may significantly affect the yields of individual wells.       Water from the Pocono and Pottsville Formations is very low in dissolved solids but may contain undesirable amounts of iron and manganese, especially water from the Pottsville. Median dissolved solids are 52 and 53 milligrams per liter for the Pocono and Pottsville, respectively. Iron and manganese exceed drinking water standards in water from about 80 percent of the wells in the Llewellyn Formation. Wells that intercept mine water will contain 3 to 40 times the concentrations of constituents present in other areas. Excessive iron, manganese, sulfate, dissolved solids, and corrosiveness are the major properties that make mine water poor in quality.       Mining has not affected the water quality of the Maunch Chunk Formation nor significantly changed the water quality of the Pottsville Formation distant from mines. Return to the Water Resources of Pennsylvania Home Page or go directly to: The URL for this page is http://pa.water.usgs.gov /abstracts/wrr_64.html Please note our privacy statement and disclaimer Accessibility Answers to many common questions can be found on our Frequently Asked Questions (FAQ) page. Please direct content comments or questions to: Information Specialist U.S. Geological Survey 215 Limekiln Road New Cumberland, PA 17070-2424 Phone: (717) 730-6916 FAX: (717) 730-6997 Email: is_pa@usgs.gov or contact: Director, USGS Pennsylvania Water Science Center U.S. Geological Survey 215 Limekiln Road New Cumberland, PA 17070-2424 Phone: (717) 730-6960 FAX: (717) 730-6997 Email: dc_pa@usgs.gov Please direct web related comments to webmaster@pa.water.usgs.gov caww50