f/EPA
                                United States
                                Environmental Protection
                                Agency
                                Environmental Research
                                Laboratory
                                Athens GA 30613
                                Research and Development
                                EPA-600/S3-80-087  July 1981
Project  Summary
                                Effect  of  Agricultural  Land
                                Development on  Drainage
                                Waters in the North  Carolina
                                Tidewater Region

                                R. W. Skaggs, J. W. Gilliam, T. J. Sheets, and J. S. Barnes
                                  In a three-year study, the effect of
                                agricultural drainage and develop-
                                ment on hydrology and the effect of
                                runoff water quality on high organic
                                soils were examined in the North
                                Carolina Tidewater Region. A small
                                but significant increase was found in
                                organic nitrogen in drainage water as a
                                result of agricultural development.
                                True organic soils lost considerably
                                more phosphorus to drainage waters.
                                Development caused  a decrease in
                                evapotranspiration with a consequent
                                small increase in annual outflow even
                                during years when droughts occurred.
                                Dissolved oxygen, biochemical oxygen
                                demand, temperature,  pH, and other
                                water quality parameters exhibited
                                relatively small changes as a result of
                                development. A significant increase in
                                the loss of fecal and total coliform
                                bacteria from pasture land was ob-
                                served, which represents a  potential
                                water quality problem.  Studies of the
                                herbicide alachlor showed that it
                                disappeared rapidly from soil after
                                application but also showed that low,
                                nonphytotoxic concentrations per-
                                sisted from one season to the next.
                                High concentrations in drainage waters
                                appeared to be caused by direct spray-
                                ing or by spray drift. Soil subsidence
                                was greatest immediately after devel-
                                opment.
                                  This Project Summary was devel-
                            US EPA Headquarters Library
                            401MSI..SW    (3404)
                            Washington, DC 20460

                                oped by EPA's Environmental Research
                                Laboratory, Athens, GA, to announce
                                key findings of the research project
                                that is fully documented in a separate
                                report of the same title (see Project
                                Report ordering information at back).

                                Introduction
                                  Land in the Tidewater Reg ion of North
                                Carolina is flat, with surface elevations
                                of only a few meters  above sea level.
                                The water table is close to surface and,
                                under natural conditions, large areas of
                                the region are swampy. Many of the
                                soils are organic or have high organic
                                surface layers. These  soils, which are
                                referred  to cumulatively as the Black-
                                lands, present several specific and
                                unique agricultural problems. Drainage,
                                which is essential for  agricultural pro-
                                duction in the region, was first initiated
                                in the late 1600s. Since that time,
                                periods of clearing and development
                                have been followed by  longer periods of
                                inactivity.
                                  The latest period of increased drainage
                                activity began in the early 1970s when
                                several  large corporations became
                                involved in clearing  and developing
                                thousands of hectares of land in eastern
                                North Carolina. This  developmental
                                activity coincided with  the algae bloom
                                problems in the Chowan River  and the
                                general awareness that development of
                                any type results in some environmental

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changes. Consequently, it is natural and
appropriate that questions were raised
by the scientific community, by various
state and federal agencies and by the
general public, about the effect that
massive land changes would have upon
the environment.
  One specific concern was the effect of
land development on the  rate and time
distribution of runoff with some appre-
hensions that greatly increased peak
rates would surpass the capacity  of
existing outlet canals and rivers. The
land under development  lies between
the Albemarle  and Pamlico  estuaries,
which are important for both commercial
and sport fishing. State agencies were
concerned that these estuaries might be
damaged through increased sedimenta-
tion from the developing lands, increased
nutrient flux into the estuaries causing
algal blooms, a change in organic matter
entry into estuaries, pesticide move-
ment into the water, increased input of
fecal organisms from pasture lands,
increased heavy-metal concentrations,
and a change in the freshwater distribu-
tion resulting in detrimental effects on
salt water organisms because of de-
creased salinity. Others expressed con-
cern that clearing  and drainage would
cause a large increase in oxidation  of
the organic matter  in the soils resulting
in a general subsidence of the land
surface.
  In attempting to address potential
problems and to assess  the environ-
mental impact of the planned activities,
it was recognized that there was a void
in basic scientific information concern-
ing the effects of clearing and develop-
ment on the hydrology and quality of the
drainage waters from organic and high
organic mineral soils. A research project
was developed to  study those effects.
The project was sponsored by the U.S.
Environmental  Protection Agency, the
North Carolina Water Resource Research
Institute  through the matching grants
program  with  the  Office  of Water Re-
search and Technology, and the North
Carolina Agricultural Research Service.

Procedure
  Experiments were conducted on paired
developed and undeveloped sites of
three different soils that span the range
of soils being developed in the Tidewater
Region (Blacklands).
  Dashboard riser structures with weirs
were installed at the drainage outlets of
each of the six experimental sites. The
triangular weirs were calibrated in
place, and outflow rates were measured
continuously by recording the stage
upstream from the weirs. A flow-pro-
portional automatic water sampler was
located at each  site for  collection of
water  samples.  The  stage  recorders
were serviced weekly and water samples
were  collected at the same time for
laboratory analyses. Rainfall was con-
tinuously recorded at each site. Water
tables were also continuously recorded
on each site at points midway between
field drains. Field measurements of
conductivity, salinity, dissolved oxygen,
temperature, and pH were made on grab
samples taken at the weekly sampling
times. Laboratory measurements of
total P, total N, nitrate-nitrogen, total
organic carbon,  filterable solids,  and
turbidity were run on the weekly samples.
Analyses for Ca, Mg, Na, Cu, Fe, Mn, Cd
and Zn were run on composite samples
at monthly  intervals. Fecal and total
coliforms were run on grab samples
taken every two weeks.
  Pesticide application during the study
consisted almost entirely of alachlor [2-
chloro-2, 6-diethyl-N-(methoxymethyl)
acetanilide].  Samples of soil were taken
for the first four weeks after application.
Runoff samples were collected  during
and after two to five rainfall events
following pesticide application. The
water  samples were field processed
with a XAD-2 macroreticular resin and
transorted to the laboratory for analyses.

Results
  Peak runoff  rates occur earlier and
are three to four times higher on devel-
oped as on similar undeveloped lands.
As presently designed, the drainage
canal  network,  with pump-assisted
outlets in some cases, does not have the
capacity to remove the water at the rate
that it  can drain from developed fields.
As a result there may be little difference
between runoff rates from developed
and undeveloped lands during the
largest runoff events.
  Total annual outflows from the devel-
oped sites were somewhat higher than
from undeveloped sites during certain
years of the study, but about the same in
others. In general, however, develop-
ment  will cause  a decrease in evapo-
transpiration (ET) with a consequent
increase in annual runoff during years
in which drought  periods occur. The
increase in total  runoff will usually be
small but will depend on the number of
droughts that are followed by runoff-
producing rainfalls.
  Drainage systems currently installed
in the organic and high organic mineral
 soils provide mostly surface rather thaw
 subsurface drainage. Water tables are
 usually close to the surface during the
 winter and change continuously with ET
 and rainfall during the growing season.
 Average water table depths were about
 22-cm deeper on the developed than on
 the undeveloped deep organic soil.
 Because of the influence of the root mat,
 water  tables were actually deeper on
 ditched, but undeveloped,  mineral and
 shallow organic soils.
  The  composition of drainage water
 from agricultural fields in the organic
 and high organic soils of the Blacklands
 is somewhat different from other agri-
 cultural areas of North Carolina. Conse-
 quently, the effect of development of
 natural areas for agricultural production
 is different. Much less inorganic nitrogen
 is found in drainage water from devel-
 oped fields  in the Blacklands'as com-
 pared to most fields further inland. This
 is a result of the very low nitrate levels in
 drainage waters from these organic rich
 soils. The inorganic nitrogen losses to
 drainage water from developed areas
 are greater than from natural areas, but
 the increase in nitrogen concentration
 is not  as  large as might be predicted
 based  on  data  from other agricultural
 areas.
  The largest potential eutrophication
 hazard resulting from development may
 be the  increase in phosphorus in drain-
 age waters.  The effect of development
 upon phosphorus losses  in drainage
 waters is dependent  upon soil type.
 Inorganic soils react with fertilizer
 phosphorus to prevent its loss. The
 solubility of phosphorus in  shallow and
 deep organic soils is much greater than
 in inorganic soils, so much of the added
 phosphorus can be lost to drainage
 water.  The weighted average concen-
 tration in drainage waters from the two
 developed organic soils was 1 to 2.5
 mg/l for a total phosphorus efflux of 7 to
 10  kg  ha"1  yr"1. The  amount of this
 phosphorus reaching major streams or
 estuaries will depend  on the distance
 the water must travel  to reach  the
 outlet,  the  type of sediment in  the
 collector ditches, and the soil material in
the banks. If the sediments are from
 inorganic soils or the canals are cut into
 mineral layers,  much of the inorganic
orthophosphate may be removed from
sol ution by these sediments. Fortu nately,
 much of the  current agricultural devel-
opment is on mineral  soils where P
 losses are small. It should be recognized
 however, that agricultural developmerl
of organic soils that are low in mineral

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iontent and immediately adjacent to
estuaries or major streams will signifi-
cantly increase the entry of phosphorus
into these waters.
  The Blackland soils are flat so erosion
is not a problem, but development does
cause a small increase in sediment load
of drainage waters. This increase is
particularly apparent during the devel-
opmental phase. Turbidity of the drain-
age water is increased during clearing
and land shaping. Once initial develop-
ment is completed, erosion and turbidity
during normal agricultural production is
not likely to  cause a water  quality
problem.
  Several water quality parameters are
measurably affected by development,
but the change is relatively small.  For
example, dissolved oxygen, biochemical
oxygen demand, and pH are all slightly
higher in drainage water from developed
areas. Other parameters that change
upon development but are not generally
considered critical in evaluation of
water quality in this region are Ca, Mg,
Cl,  Na, and  K. Development has little
effect upon efflux of Cu, Zn, Mn, andFe.
  One potential problem with develop-
ment  of the organic soils for pastures
Rear shell fishing waters is the loss of
veal organisms in drainage waters. The
counts of fecal and total coliform bacteria
in drainage water from the pastured site
were  considerably greater than from
natural areas. This increase in coliform
bacteria from grazed lands is common
throughout the United States and  ap-
parently causes few problems. Problems
could result, however, if grazed land is
located immediately adjacent to shell-
fish waters.  Development also caused
an  increase in coliform bacteria from
the cropped  shallow organic soil even
though no domestic animals were ever
kept on this site.
  Comparison  of elemental deposition
from the atmosphere, as compared to
losses in  drainage waters from the
natural areas, showed that three to four
times as much N and P were deposited
as was lost in drainage waters. The
deposition of Na, Cl, K, Ca, Mg, Cu, Mn,
and Zn was approximately the same as
removal in drainage waters. There was
a net  loss of Fe from the natural areas.
  The high organic matter content soils
in eastern North Carolina require special
sampling techniques to provide reliable
estimates of the amount of pesticides
applied. The most effective method of
  fnfirming the rate of deposition of the
  rbicide alachlor was the use of filter
  per discs laid on the soil surface
during application.
  Alachlor residues among individual
soil samples taken after herbicide appli-
cation were highly  variable, but an
average of seven or  more samples
within a plot or analysis of a composite
sample from seven sites  within a plot
appeared to provide a reliable estimate
of the residue level.
  Residues of alachlor (parent com-
pound) disappeared rapidly after appli-
cation to the organic soil;  however, low
levels of "apparent"  alachlor persisted
from one season to the next in a biologi-
cally inactive form. There was no signifi-
cant accumulation of alachlor  residue
above the  detectable, but  very low con-
centrations, that carried over. Transport
of alachlor, and probably other pesticides
as well in surface  runoff from the high-
organic soils of the Tidewater Region of
eastern North Carolina and  similar
areas elsewhere, does not appear to
pose a significant hazard to aquatic life.
  Concentrations of alachlor in drainage
water after application  suggested that
some applicators were  careful to avoid
spraying the V-ditches  draining the
fields but that some may  have sprayed
directly over them,  or so close that
heavy drift of sprays occurred, causing
excessively high  concentrations of
herbicide in drainage water during the
first few days after some applications.
More diligence and care during applica-
tion of  all  pesticides used on many
farms in the Tidewater Region of North
Carolina, where ecologically sensitive
areas  exist in close proximity to  large
agricultural areas, would reduce or
even eliminate significant hazards
caused  by  direct spraying  of,  or drift
onto, water in drainage canals.
  The major effects of  agricultural
development on soil properties involved
the surface horizon. Development re-
moved the root mat and decreased the
surface  elevation. The  bulk density of
the surface horizon increased and the
porosity decreased. Both hydraulic
conductivity and drainable porosity are
decreased  during  the developmental
process. The effects of development on
all soil properties  increased with the
depth  of the organic layer.
  Subsidence  of the organic soils is
greatest directly after development
because of irreversible drying and
shrinkage of soil in the root  zone. After
this initial  period,  subsidence on the
deep organic pasture site was less than
1 mm/year for a three-year period.
   R.  W. Skaggs, J. W. Gilliam, and T. J. Sheets are with North Carolina State
     University. Raleigh. NC 27650; J. S.  Barnes is with First  Colony Farms,
     Creswell. NC 27928.
   C. N. Smith is the EPA Project Officer (see below).
   The complete report, entitled "Effect of Agricultural Land Development on
     Drainage Waters  in  the  North  Carolina  Tidewater  Region." (Order No.
     PB 81-105 959; Cost: $21.50. subject to change! wilt be available only from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield.  VA 22161
           Telephone: 703-487-4650
   The EPA Project Officer can be contacted at:
           Environmental Research Laboratory
           U.S. Environmental Protection Agency
           Athens, GA  30613
                                                                                       » US. GOVERNMENT PRINTING OFFICE: tWl -757-012/7206

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