The Yorktown-Eastover aquifer system is a multiaquifer unit consisting of late Miocene and Pliocene deposits and is composed of the sandy facies of the Yorktown and Eastover Formations (Meng and Harsh, 1988). The Yorktown-Eastover aquifer system consists of a series of alternating sand and clay-silt units that form three distinct aquifers that generally are present throughout the Eastern Shore. These aquifers are identified as the upper, middle, and lower Yorktown-Eastover aquifers. Correspondingly, each aquifer is overlain by the upper, middle, and lower Yorktown-Eastover confining units. The entire aquifer system is wedge shaped and thickens and dips eastward. The units extend eastward beneath the Atlantic Ocean to the continental shelf and westward underneath the Chesapeake Bay(source USGS).
Nearly all drinking water on the Eastern Shore of Virginia is derived from groundwater as there are no surface water bodies capable of supplying a large quantity of water. Most residents obtain their drinking water from private wells since the percentage of housing units in Accomack county having water supplied by a public water system is listed at 31% (out of 15,840 units) in the most recent U.S. Census data; for Northampton county the figure is 12% (out of 6,183 units). Municipal wells are usually completed in the Yorktown- Eastover aquifer system, typically with multi-screened wells. Total ground water use was estimated to be 5 million gallons per day (Mgal/d) by the U.S. Geological Survey and using records contained within the EPA Federal Data Reporting System. A population of approximately 52,000 is served by public water supply systems (which rely on ground water). Withdrawals by private wells from the Columbia were estimated to be at least 1.7 Mgal/day. Other large ground water withdrawals include those for industry and irrigation (DEQ, USGS).
The quality of ground water in Accomack and Northampton counties is considered above average in quality, but the highly permeable nature of the aquifer material and the shallow depths to the water table reduce the capacity for contaminant attenuation, making the aquifer vulnerable to contamination from point and nonpoint sources. The Columbia aquifer is especially vulnerable to potential sources of contamination. Ground water data collected for the surficial aquifer on Delmarva peninsula indicates ground water quality has been affected by human activities. These impacts include statistically significant increases in dissolved minerals, elevated nitrate levels and pesticide residue detections.
Use of alternative supplies of water outside the aquifer is economically and technically not possible due to the difficulties and costs of transporting water from either mainland Virginia or northerly portions of the Delmarva peninsula. In addition, excess alternative ground water supplies in nearby portions of mainland Virginia are unlikely to be available, as shown by current difficulties in obtaining additional water for Virginia Beach, VA.
|Water to Land Ratios by County|
|County||Total land Mass||Amount of dry land||Amount of water||% of water to land|
|Northampton||795 sq. miles||212 sq miles||584 sq. miles||73.5%|
|Accomack||1,310 sq. miles||450 sq miles||861 sq. miles||65.7%|
|Somerset||610 sq. miles||321 sq miles||291 sq. miles||48%|
|Wicomico||400 sq. miles||374 sq miles||26 sq. miles||6.4%|
|*Water to Land Ratios courtesy of Ken Dufty|
Given the sensitive nature of our sole source aquifer, and geographic sensitivity(% water to land ratio), attempts by Northampton County to compare our county other counties in our state and beyond, as a way to determine a consistant methodology for protecting our natural resources in the least restrictive way seems counter productive to the current economic successes we have recently been seeing (tourism and aquaculture). The chart above notes that Northampton County has more surface water per square mile than any other county.
Note: Even as Northampton has a 73.5% water to land mass ratio as compared toWicomico’s % of (6.4%), Maryland, due to what it considers sensitive nature of that location (Wicomico), is in the process of implementing measures that will place a ban on the land application of chicken manure, as a means to runoff of phosphates and nitrates.