By Brad Haire
University of Georgia
Environmental policymakers say many Georgia streams don’t have
enough oxygen. This is an environmental problem that must be
fixed. But in some cases, it could be a safe, natural
occurrence. Scientists in Tifton, Ga., are working to help
policymakers better regulate the health of Georgia streams.
Like humans, fish and other aquatic life need oxygen to survive.
They get it from dissolved oxygen (DO) in the water around them,
said George Vellidis, an engineer with the UGA College of
Agricultural and Environmental Sciences. DO is also essential
for the breakdown of pollutants and organic matter in streams.
“If the DO level is too low in a stream or in some other water
body,” he said, “the fish and aquatic life can become stressed
or die.”
The standard
That’s why the Georgia Department of Natural Resources –
Environmental Protection Division established a DO standard for
Georgia’s streams. If a stream’s DO level drops below 4
milligrams per liter, the stream is considered in violation.
The Clean Water Act of 1972 was enacted to control water quality
problems like low DO levels in U.S. waters. Until recently, not
much was done to address the problem in many parts of the
country.
Environmental groups are now putting legal pressure on Georgia
and other states to create and implement plans to fix DO-
challenged streams, Vellidis said.
The data on DO levels in Georgia streams in many cases is not
current. The most recent data for some streams in south Georgia
is several years old. Environmental regulations based on this
data could be wrong, Vellidis said.
Natural answers
He and a team of UGA and U.S. Department of Agriculture
scientists on the UGA Tifton, Ga., campus discovered that DO
levels in streams in south Georgia can rise or fall naturally
below the current standard many times throughout a year. And
fish are probably well adapted for the changes.
DO levels for many streams drop during hot summer months or
during times of low water flow like in times of drought, he
said. These levels can also be affected by the amount of
sunlight hitting the water or by excessive amounts of nutrients
like farm fertilizers, he said.
(Nutrients encourage algal growth. Algae release oxygen into the
water. But algae live a short time. When they die in large
quantities, the microorganisms that decompose them use a lot of
oxygen and quickly lower the DO level.)
Agricultural practices are often blamed for increased nutrient
levels and low DO levels in streams and rivers. To bring problem
streams into compliance, Vellidis said, some preliminary plans
recommend reducing nutrient levels in streams and rivers by as
much as 40 percent. This reduction would likely be expected to
come primarily from agricultural sources.
This would be an economic blow for agricultural regions of
Georgia and, possibly, an unnecessary step if it is natural at
certain times of the year for a stream to be below the current
DO standard, he said.
Agricultural fertilizers and chemicals probably do contribute to
low DO levels, he said. But there are many other factors that
must be considered.
Vellidis and the research team are undertaking an extensive DO
level study in the Coastal Plain area of Georgia. They are
setting up monitoring sites in the Ochlockonee, Suwannee,
Satilla and St. Mary’s river basins to take samples and measure
factors that contribute to DO levels. Georgia DNR-EPD is funding
the three-year project.
State environmental policymakers can use this new data to make
sound DO standards and avoid creating unnecessary, harmful
policies.
