Million Year Old Groundwater In Maryland Water SupplyJune 18, 2012
A portion of the groundwater in the upper Patapsco aquifer underlying Maryland is over a million years old. A new study suggests that this ancient groundwater, a vital source of freshwater supplies for the region east of Washington, D.C. and Baltimore, was recharged over periods of time much greater than human timescales. "Understanding the average age of groundwater allows scientists to estimate at what rate water is re-entering the aquifer to replace the water we are currently extracting for human use," explained USGS Director Marcia McNutt. "This is the first step in designing sustainable practices of aquifer management that take into account the added challenges of sea level rise and increased human demand for quality water supplies." This new study from the USGS, the Maryland Geological Survey (MGS) and the Maryland Department of the Environment (MDE) documents for the first time the occurrence of groundwater that is more than one million years old in a major water-supply aquifer along the Atlantic Coast. The oldest groundwater was found in the deepest parts of the aquifer, but groundwater even in shallower parts of the aquifer is tens to hundreds of thousands years old. Groundwater age indicates the length of time that a sample of water has been in the ground since infiltrating from the land surface. This study reveals that modern pumping in southern Maryland west of the Chesapeake Bay and on the Eastern Shore is tapping groundwater resources that have accumulated in the aquifer over multiple cycles of climate change and are not quickly recharging. The analysis shows that water flowed from the land surface into
the deep aquifer during cooler periods in earth's history, when
glaciers covered much of the northeastern U.S. and sea level was
about 125 meters lower than it is today. During warmer periods in
earth’s history, such as in modern times, higher sea levels slow
recharge of fresh water to the aquifer, due to a lower gradient
between the recharge and discharge areas. The findings are being used to help understand the patterns and rates of groundwater movement in the aquifers of the Coastal Plain. Such information will be used by the Maryland Department of the Environment to ensure that the management and use of the State's groundwater resources are being carried out to protect its long-term sustainability. The findings bring into focus that current users are withdrawing groundwater that was recharged eons ago and accentuate the need to review current water-supply management strategies and develop new tools and models to protect this valuable resource for the future. There are relatively few aquifers in the world in which million-year-old groundwater has been documented, including the Nubian aquifer in the Sahara Desert, Canada's Alberta Basin, and the Great Artesian Basin in Australia Aquifer sustainability is one of several priority topics currently being addressed by the USGS Groundwater Resources Program, the USGS National Research Program, and the USGS Cooperative Water Program. More information about the study is available online(http://www.springerlink.com/content/j08u34jh46r632v4/?MUD=MP) SOURCE: USGS Copyright © 1996 - 2012, VertMarkets, Inc. All rights reserved. To subscribe or visit go to: http://www.wateronline.com |