Pennsylvania groundwater recharge information available in user-friendly report
Harrisburg – The month of April is known for rain showers, but a
new Pennsylvania Geological Survey report says that the state’s
groundwater actually recharges the most during March.
The report, “Summary of Groundwater-Recharge Estimates for
Pennsylvania,” was done in cooperation with the U.S. Geological
Survey and is available on the Department of Conservation and
Natural Resources’ Web site at www.dcnr.state.pa.us/topogeo/.
“This report is a convenient source of groundwater recharge data
for researchers, water resource managers, water scientists and
geologists. It provides a general overview of processes affecting
groundwater recharge in Pennsylvania and a discussion of estimates
of recharge rates,” said Jay Parrish, the state geologist with
DNCR. “It’s also a great educational resource because it shows
where all of the water that falls from the sky goes.”
Recharge occurs when water reaches underground aquifers. It is
typically estimated by measuring factors including precipitation
and stream flow.
Areas that receive the most recharge are typically those that
get the most rainfall, have favorable surface conditions for
infiltration, and are less susceptible to the influences of high
temperatures, evaporation and loss through vegetation.
Maps included in the report illustrate patterns of
precipitation, temperature, prevailing winds, and the average error
associated with recharge estimates.
In an average year, about 40 inches of precipitation – the rough
equivalent of 31.5 trillion gallons of water — falls in
Pennsylvania. Only about 31 percent of rainfall is absorbed by the
land to become groundwater. Of the rest, 52 percent evaporates and
17 percent becomes runoff into rivers and streams.
Eighty percent of Pennsylvania’s recharge occurs from November
to May, with approximately 18.4 percent coming in March followed by
nearly 13 percent in April.
For more information about geology in Pennsylvania, visit the
DCNR Web site at www.dcnr.state.pa.us and choose
“Geology” at the bottom, or call (717)702-2073.