Southeast
groundwater pollution feared
By Robinson Shaw
New evidence shows the water
feeding Ichetucknee Springs flows through a
groundwater system of small porous rocks, not
underground conduits, raising concerns about water
pollution throughout the state. |
Rivers and streams in north Florida often
disappear into the ground, only to reemerge in another
location, a result of the porous rock formations that lie
just underneath the ground.
Recently a University of Florida geologist
found evidence that the river and stream water feeding
Florida's many springs travels through a different
underground system that could lessen the quality of drinking
water in north Florida and throughout the Southeast.
The water feeding North Florida's springs
flows through tiny pores in the rocks, not large underwater
conduits, according to Dr. Jon Martin, assistant professor
of geology at the university. "The rocks are really
porous and there are a lot of open spaces filled with water.
The question was, does the river flow off the surface into a
conduit (a large underground water cave) then up to the
surface, or into a groundwater system through small open
spaces," said Martin. "These are where private
wells are located, in the small open spaces."
A conduit is not a source of drinking
water and water flowing from a river or stream into a
conduit usually flows fast, said Martin. However, water
flowing underground into the small open spaces is exchanged
for water that's been sitting in the pores for years,
sometimes hundreds of years allowing pollution to build up.
This pollution could be coming up through wells and into
homes as drinking water or through natural springs.
"The real problem is how long does
the water and associated pollutants remain below the
surface, and then where does it go?" said Martin.
"The pollution can get in the groundwater and be there
for tens of years or hundreds of years."
"Many people in the area see their
water quality change during storms," said Martin.
"Anyone in that area (north Florida) should have their
well water tested."
"When people drill a well 200 feet
down, they think it's clean groundwater that's been there
for 200 years and nothing is wrong with it, but that's
probably not true," said Martin. "Any groundwater
near the surface has the potential to be contaminated."
Brian Katz, a research hydrologist at the
U.S. Geological Survey in Tallahassee, said Martin's
findings bolster the case for keeping pollution away from a
wide geographical area around springs. "His research
and other research clearly demonstrates that you need to
look beyond the sink (where river water sinks underground)
or the spring and protect the entire source area," he
said
For part of the research, Martin used
automated equipment to make repeated temperature readings at
the Santa Fe River's sink and rise (where it reappears)
along the Alachua-Columbia county line, as well as at lake a
between the two. Santa Fe's rise is considered one of
Florida's 38 largest, or first-magnitude, springs.
The researchers matched the temperature
data with samples of the chemical composition of the water
at private water wells near the sink and rise to determine
if the river water sinking underground was flowing into
private wells or conduits. They took measurements when the
river was flowing normally, when it was flooding and when a
flood was ebbing.
Martin and other researchers took more
than 15 million temperature readings for one year beginning
January 1998 and is just now completing an analysis of the
data. His conclusion: The underground "pipe"
between the Santa Fe's sink and rise — actually a series
of connections in the porous limestone — may lose or gain
a significant amount of water when the river is flowing
normally. "The water can leak into the conduits, and it
can leak out of the conduits," he said.
Temperature and chemical
readings were taken of two Florida rivers. The
results indicate water in private wells could
contain pollutants from surface rivers and streams. |
During floods, the water flows into the
small porous spaces and the conduit loses water, which
corresponds with anecdotal evidence pointing to an influx of
water in wells during floods. "People in this area say
that when it rains, their well water gets muddy," he
said.
The other important implication of the
research is that it calls into question one of the terms of
a recent settlement between the state of Florida and a
cement company that plans to build a plant near the
Ichetucknee Springs State Park, a popular recreational
destination in Suwannee County, said Martin.
The Florida Department of Environmental
Protection last week agreed to allow the company, Anderson
Columbia Co. of Lake City, to build the plant in part on
condition it sell a lime rock mine north of the springs.
State officials feared the mine could impede or cut off the
springs' water source, but Martin said his research shows
the mine may not impact the springs one way or the other.
The results suggest "the water coming
out of those springs is not fed by an extensive conduit
system. Much of the water discharging from the springs comes
from the micro pore systems," Martin said.
Although Martin's research contrasts with
results of most other scientific studies of the porous rock
formation called karst aquifers of the Southeast, those
studies focused on the western Appalachians, which have far
older karst systems, said Martin. The other studies showed
the rock of underwater conduits to be far less permeable.
"Those places have much older rocks,
so much of the porosity has been filled up," he said.
"In Florida and other parts of the Southeast such as
South Carolina and Georgia, the karst systems are much
younger, so that hasn't happened yet."
Copyright 1999,
Environmental News Network, All Rights Reserved
Related Links:
Martin is an associate geology professor
at the University
of Florida.
The USGS
is the government agency for geologic research in the U.S.
The Geologylink
offers lots of information on "all matters
geological."
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