United States
Environmental Protection
Chesapeake Bay
Annapolis MD 21403
Research and Development
EPA-600/S3-83-078  Nov. 1983
Project  Summary
Ware  River Intensive Watershed

Gary F. Anderson, Cindy Bosco, and Bruce Neilson
  The Ware River Intensive Watershed
Study includes examinations of runoff
from small catchments, instream trans-
port of runoff, and  their impacts on
estuarine water quality.
  Runoff quantity and quality were
monitored for row crop, residential and
forested lands in the Ware basin for the
period  of October 1979 to July 1981.
Loading rates have been calculated for
both baseflow and stormflow contri-
butions at each study site.
  Concentrations increased during
stormflow periods for all water quality
constituents except dissolved silica. On
the average, this increase was an order
of magnitude greater than the baseflow
concentrations for particulate mate-
rials, and  by  a factor of two for dis-
solved constituents. Concentrations of
total phosphorus, nitrogen, and dis-
solved ammonia  were substantially
higher  in the runoff at the two agri-
cultural sites than at the residential and
forested catchments. The residential
catchment had high  concentrations of
dissolved nutrients and BOD5 in both
baseflow and storm runoff. Area! load-
ing rates were more a function of runoff
quantity than concentration. The resi-
dential site, which produced the great-
est amount of storm runoff, also had the
highest loading rates for all constit-
uents  except phosphorus and sus-
pended solids. The well drained upland
farm produced the least runoff of the
four catchments monitored.
  Baseflow accounted for a significant
portion of the total flow at the forested
and residential catchments, especially
during  winter months when the water
was high. Nearly half of the total flow
came from ground water during the study
period. However, storm runoff produced
83 and 70 percent of the total phos-
phorus and nitrogen loads, and 62 and
91 percent of the BOD5 and suspended
solids loads,  respectively.  Although
only 13 of 114 site-events had rainfall
greater than 5 cm, these accounted for
more than 50  percent of the measured
storm runoff.
  Results from the study of estuarine
waters indicate that the Ware River con-
tains a moderate amount  of nutrients.
However, during summer months,
some of the nutrients, particularly inor-
ganic phosphorus and organic nitrogen,
reach levels associated with moderate
enrichment. The Ware is typical of other
small tributaries of Chesapeake Bay:
nutrient levels  are higher at low tide, the
estuary is more homogenous laterally
than longitudinally (with respect to nu-
trients), and vertical gradients exist for
dissolved  oxygen, total phosphorus,
and suspended solids.
  The phytoplankton are generally
phosphorus limited, except during the
annual spring phytoplankton blooms
(April 1979 and March  1980), when
uptake of inorganic nitrogen by plankton
causes the system to be nitrogen
limited.  Impacts of nonpoint source
pollution  are  slight and short-lived in
the estuary. This appears  to be due to
dilution by Bay waters and sedimenta-
tion in the upstream marshes. Thus, im-
pacts are typically observed only in the
shallow  upstream  portions of the
  This Project  Summary was developed
by EPA's Chesapeake Bay Program,
Annapolis, MD, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).

  The  objective of the  Ware River
Intensive Watershed Study was to
characterize the contribution of various
land uses to the nonpoint source loadings
into the Ware River and Chesapeake Bay.
The quality and quantity of runoff for the
major land uses and physiologic features
of the watershed were measured over a
two-year period. During that period, the
nature, extent,  and duration of storm
water impacts on the water quality of the
Ware River estuary were also measured.

Procedure/ Methodology
   The  sites  selected for the study were
occupied  by land uses typical of the
Chesapeake Bay region: a forested site, a
residential site, and two row-crop agricul-
ture sites. These types of uses occupy a-
bout 87 percent of the land area in the Ware
   The  undisturbed, mixed forest site was
selected primarily  because the catch-
ment was exclusively forested yet easily
accessible for study. It has moderate
slopes but poorly drained soils underlying
the debris on the forest floor.
   The  low  density  residential site  is
occupied by a small subdivision located
adjacent to the shoreline of the estuary. It
was selected in part because the homes
have septic tanks and stormwater runoff
control through a  series of  roadside
   The  two row-crop agricultural sites are
in typical  corn and soybean rotation us-
ing fertilizer application and herbicides
to control weeds. The lowland  site has
poorly drained soils, whereas the upland
soils are light, erosive, and well  drained.
Relief  is more pronounced at the upland
   Of the four sites, three have continuous
base flows during winter due to high wa-
ter table conditions.  The upland agricul-
ture site exhibits no baseflow. Flows at all
sites  were  monitored by  installing H-
flumes in the drainage-ways.
   Flowmeters  were installed  at each
flume  to continuously monitor baseflow
and stormflow conditions. Automatic
composite water samplers were used.
The sample was paced by  the flowmeter
to deliver an aliquot of sample to a single
container at a pre-set increment of flow.
In addition to runoff monitoring instru-
ments, a  recording  rain gauge sensitive
to 0.01 inch was installed  at each site.
   Samples were routinely collected
during dry  periods when baseflow
occurred in order to characterize loadings
during non-storm conditions. Base flow
and runoff  samples were analyzed for
total and dissolved phosphorus, total and
dissolved Kjeldahl nitrogen, BODs, sus-
pended  solids, total and  dissolved  am-
monia  nitrate-nitrite  nitrogen, and  dis-
solved silica.
  Estuarine water quality was studied to
determine how it is affected  by runoff.
Sampling stations were established
throughout the Ware River estuary and
were sampled semi-monthly throughout
the 27-month study with runabouts;
submersible pumps were used to bring
sample water on board. In addition,
several intensive  surveys were con-
ducted on the River to provide a compre-
hensive picture of how water quality va-
ries temporally and spatially in response
to various inputs. Monitoring was con-
ducted to study the die! nutrient dynamics
surrounding  the spring  chlorophyll a
maximum  and  the  response  of  the
estuary to sunlight, tidal oscillation, and
organic pulse loads caused by runoff.

  Results of the land-use studies can be
summarized in two ways: 1) the individ-
ual loads for each site are summed for all
the events monitored during the 22-
month   period, and 2) each  individual
storm load is divided by the rainfall for
that particular event to yielda mass pollu-
tant per unit rainfall value for each storm.
The second method is important because
a statistical representation of the storms
can be made and compared, as well as ex-
trapolated to other years and other rain-
fall records. The first only provides an ab-
solute comparison among the sites.
  Although nutrient concentrations in
runoff from both agriculture sites were
significantly higher than at the other two
sites,  so little runoff occurred that the
total loadings are lower than at either the
forest  or residential catchment.  The
reduced flow (an  order  of magnitude
below the other sites, probably due to the
fact that much of the rainwater is lost to
percolation into  the  rapidly permeable
soils)  more than compensated  for the
higher  pollutant concentrations  in the
runoff.  An exception  is phosphorus,
however, that was highly enriched in
runoff  from the cultivated fields. Sus-
pended solids coming from the denuded
land were also very high.
  The forest and the lowland residential
sites have significant per area baseflow
which  was comparable in quality.  The
baseflow loading at these two sites was
quite significant.  Some of thesimilarity in
water quality could be the result of the
large number of  trees on both occupied
and vacant  lots in the subdivision.
Stormflow from the residential site,
however, was greater than that from the
forest on an areal basis. The manmade
ditches and impervious surfaces (about
10 percent of the surface area at the
residential  site)  were expected to ac-
celerate  surface  runoff  there. Since
nutrient concentrations were generally
higher in stormflow, the stormflow load-
ing  rates  and combined  loading rates
were  higher for  the residential catch-
ment. Another notable feature of the resi-
dential catchment was the high loading of
dissolved nutrients in baseflow, particu-
larly orthophosphorus and nitrite-nitrate.
This striking difference  between  the
baseflow quality of residential  and
forested catchments may be due to leach-
ing from nearby septic tank drainfields in
the residential area.  •      •   • •   •
  Baseflow accounted for  35 to 60 per-
cent of the total flow from the forested
and residential sites. However, because
nutrient levels  were higher in  runoff,
roughly  70 percent of the phosphorus,
nitrogen, and BOD5, and over 90 percent
of the suspended solids loadings oc-
curred during  stormflow.  If  the  upland
agriculture site were considered as well,
these values would increase, since no
baseflow was observed at the site during
the study.
  Dissolved silica is lower in runoff
because it is undetectable in rainwater.
The source of  this nutrient  is  the
weathering of mineral particles, partic-
ularly that caused by the groundwater
flowing  through  soils. Therefore,  both
loads and concentration are  higher dur-
ing baseflow,  although  silica  is  still
present during stormflows, when surface
runoff and silica rich groundwater are
combined. The silica loading rate from the
upland agriculture site was negligible,
since there was no groundwater contri-
bution to the surface flow there.
  Loading rates have been calculated for
individual storms which account not only
for  the catchment size  but also the
amount of rainfall. From these statistics,
valid comparisons can be made which
utilize the few storms sampled at the two
agriculture sites. Although the two
agriculture sites did result in the highest
individual storm loading rate, the mean
and median rates were greatest for the
storms at the residential catchment. That
is, most of the time the loading rate is
highest at the residential catchment and,
occasionally, a very high rate occurs at
the other sites. Occasional high rates are
important and were responsible for  most
of the total load  at the two agriculture
sites.  Analysis of  individual storms did
not show any relationship between
amount of rainfall and runoff or loading.

  Nutrient concentrations are generally
low in the Ware River estuary, especially
when compared to freshwater tributaries
or  to larger, more urbanized systems.
Even following significant rain  events,
extremely low nutrient concentrations for
silicates,  total  phosphorus, orthophos-
phates, suspended solids,  organic ni-
trogen, and nitrate-nitrite-nitrogen were
found in  the estuarine  mouth waters.
Moderate  nutrient enrichment  levels
were generally found upstream, where
low TN'.TP values are attributable to point
source wastewater discharge.
  Nutrient water quality at the mouth
fluctuated little with the tides; however,
temporal variations in  nutrient concen-
tration were seen elsewhere in the es-
tuary within a tidal period; especially in
the brackish region. Maximum values for
total Kjeldahl nitrogen, ammonia-nitrogen,
total organic carbon, and total phosphorus
occurred at  times of low water slack;
minimum values  were present at high
water slack. Nitrate-nitrite-nitrogen con-
centrations were generally below de-
tection limit throughout the estuary dur-
ing the survey. At no season or station
were anoxic conditions encountered in
the estuary.  However, there was a dis-
tinct longitudinal gradient present in the
estuary:  the percent saturation of dis-
solved oxygen was significantly higher at
the mouth than in the upstream reaches.
The study  average  showed 90 percent
oxygen saturation present at the mouth;
the upstream station had only 70 percent.
  Freshwater storm influence was found
to be minimal  near the mouth of the
estuary, whereas the upper  reaches of
the estuary showed significant responses
evident  in  salinity  gradients.  During
periods of increased freshwater flow,  a
two-layer circulation system may exist.
Results indicate that the estuary is essen-
tially well mixed,  predominately by tidal
processes, especially in the upper reaches.

  The impact of runoff on the Ware Riv-
er estuary appears to be slight, occasional-
ly moderate, and relatively short-lived.
Nutrient  loading of rates vary for each
land  use site and fluctuate seasonally.
The rates are a function of runoff quantity
and increase accordingly with stream-
flow.  Further study is needed to deter-
mine patterns of loading rates with rain-
fall. The  data presented can be used in
conjunction with those from other water-
shed  studies to calibrate mathematical
models of land runoff for the Bay. It is sug-
gested that further watershed studies
monitor subsurface flow to adequately
characterize low-lying coastal watersheds.
Gary F. Anderson, Cindy Bosco, and Bruce Neilson are with the Virginia Institute
  of Marine Science, Gloucester Point, VA 23062.
David Flemer is the EPA contact (see below).
The complete report consists of two  parts, entitled "Ware River Intensive
  Watershed Study:"
    "1.  Nonpoint Source Contributions," (Order No,  PB  83-253  187; Cost:
  $14.50. subject to change)
    "2.  Estuarine Receiving Water Quality," (Order No. PB 83-253 195; Cost:
    $14.50, subject to change)
The above reports are available only from: (costs subject to change):
        National Technical Information Service
        5285 Port Royal Road
        Springfield, VA 22161
        Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
        Chesapeake Bay Program
        U. S. Environmental Protection Agency
        2083 West Street, Suite 50
        Annapolis, MD 21403
                                           «US GOVERNMENT PRINTING OfFICE 1983-659-017/7217

United States
Environmental Protection
Center for Environmental Research
Cincinnati OH 45268
Official Business
Penalty for Private Use S300

                    United States
                    Environmental Protection
Environmental Research
Corvallis OR 97333
                    Research and Development
EPA-600/S3-83-079  Mar. 1984
&EPA         Project  Summary
                    Ecosystem  Responses  to
                    Alternative  Pesticides   in  the
                    Terrestrial  Environment
                    Eric Goodman, Matt Zabik, Jeffrey J. Jenkins,
                    Robert M. Kon, and Renate M. Snider
                      A conceptual model was developed
                    to describe aspects of the fate and
                    effects of a pesticide in an orchard
                    ecosystem. In order to refine, parameter-
                    ize, and test a mathematical model
                    based upon this conceptual model, a
                    program of field and laboratory experi-
                    ments was undertaken. The environmen-
                    tal behavior of azinphosmethyl was
                    studied in a Michigan apple orchard
                    watershed to gather data for the model
                    on initial distribution within the orchard,
                    vertical  movement of the  pesticide
                    under the influence of rainfall, loss from
                    the orchard with runoff, and the effects
                    of the pesticide on several invertebrate
                    populations. The estimated proportion
                    of a  low-volume application initially
                    distributed within the orchard averaged
                    .624 (standard deviation of .149) over
                    three seasons (1976-1978). Examination
                    of residues reaching each layer showed
                    the majority of the dislodgeable residues
                    were distributed to the trees and grass-
                    broadleaves. The  litter-moss and soil
                    contained residue levels roughly ten
                    times lower than  tree leaf  residues.
                    Runoff studies indicated  loss, via this
                    route, of less than 1 % azinphosmethyl
                    residues present in the orchard. The
                    generalized model  developed, entitled
                    the Pesticide Orchard Ecosystem Model
                    (POEM), includes as a special case the
                    model for the azinphosmethyl applica-
                    tions under the conditions of this field
                    study. POEM also includes facilities for
                    altering parameters to describe effects
                    of other formulations, other pesticides,
                    other application procedures and/or
                    other field conditions.
                      This Project Summary was developed
                    by EPA's Environmental Research
Laboratory, Corvallis, OR, 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).

  The work presented in the full report is
one portion of an effort to characterize the
dynamics and effects  of an example
compound in the terrestrial environment,
utilizing  primarily field measurements
and the methodology of systems modeling
and simulation.  Data collection, model
refinement, and  revised experimental
design were done iteratively, yielding a
model that is  parameterizable and data
that are  relevant to the problem being
  The study of pesticide dynamics through
in situ field studies is difficult due to the
lack of natural or planned experiments
(inability to control much of the variance,
i.e., climatic conditions) and the relatively
high levels of  error associated with field
data. Modeling techniques were employed
to  aid in the understanding  of the
necessarily large amount of field data
needed to construct a  "meaningful"
picture of the  pesticide's fate.

 The field experimental program used to
investigate the distribution, attenuation
and movement of the organophosphate
insecticide azinphosmethyl, 0,0-dimethyl-
5-(4-oxo-1,2,3,  benzotriazin-3(4H)-ylmethyl)
phosphorodithioate  (Guthion ), in a
Michigan apple  orchard is  given in
Chapter I. The compound was followed
from  its  spray application through the
orchard vegetation/litter/soil environment

  and into aquatic systems. The form of the
  model describing azinphosmethyl move-
  ment and  attenuation, as well as data
  handling  procedures and the derived
  rates, is presented in Chapter  II. Obser-
  vations were made concurrently within
  the same orchard to examine the effects
  of  azinphosmethyl  on several ground-
  dwelling invertebrates, including detailed
  studies of the isopod Trachelipusrathkei.
  Field and laboratory data collected on T.
  rathkei were used  to develop a model
  describing  its ecobiology and temporally-
  distributed pesticide-induced mortality.
  The output of the fate model described in
  Chapter II  was used to determine the
  time-course of azinphosmethyl exposure.
     In  Chapter  III the field experimental
  program used  to determine azinphos-
  methyl  airborne residues is presented. A
  multi-component kinetic model used in
  the assessment of the contribution of air-
  borne loss to the overall attenuation of de-
  posit residues is also described.
     In Chapter IV, movement and attenuation
  of  azinphosmethyl  are  examined  as  a
  function of environmental conditions. A
  computer  simulation is described which
  allows  the user to predict the fate and
  effects of azinphosmethyl  on several
  types of organisms.
     Chapter  V describes the results of the
  field sampling program for invertebrates
  in the orchard plots, providing information
  on the effects of azinphosmethyl spraying
  (additional material  on the isopod 7".
  rathkei is found in Chapter IX). Chapter VI
  contains  the  results of a laboratory
  assessment of the  toxicity of azinphos-
  methyl and diazinon to various invertebrates.
  Chapter VII briefly describes the models
  developed  for spiders, earthworms, and
  springtails.  Chapter VIM presents  a
  detailed description of the ecobiology of
  the isopod Trachelipus rathkei,  while
  Chapter IX describes the  effects of the
  azinphosmethyl spray program on the T.
       rathkei field population. Chapter X pre-
       sents the model for T. rathkei, including
       both its general life cycle and its response
       to pesticide exposure.
         Appendix A documents the data analysis
       procedures employed locally at Michigan
       State  University to parameterize  the
       model. Appendix B is the users'guide for
       the Pesticide Orchard Ecosystem Model
       (POEM) described in this report.

       (1) Further work to refine, parameterize,
       and test  the components of the POEM
       model, or similar models, for other
       pesticides and other conditions should be
       undertaken.  In  many cases, the current
       forms are derived based on sparse data in
       the literature. While predictions based on
       these  forms  may be informative and
       useful in some contexts, they  are  not
       likely to be very accurate for predicting
       actual fate and impacts of pesticides until
       they have been carefully refined based on
       currently  non-existent data. Nevertheless,
       the present model may  be  helpful,
       because  it allows the user to determine
       the  implications of various  sets  of
assumptions  about pesticide dynamics
and effects.
(2) Work on  models for the long-term
effects of pesticide exposure on populations
of invertebrates should be continued.
While this study includes a reasonable
model for effects of azinphosmethyl on
isopods and less refined models for
collembola, earthworms, and spiders, the
methodology should be extended and
refined through application to  other
pesticides and organisms.
(3) The  model presented here does not
provide an   overall indicator of the
ecosystem-level impact of a pesticide in a
particular  situation. While impacts on
individual populations are likely to be key
components  of any sound measure of
overall impact, the importance and role of
each population  in the ecosystem must
also be  defined and incorporated  in the
measure. Research aimed at  identifying
key populations and modeling their
functions should  be  undertaken. The
search  for  integrating measures  or
indicators of ecosystem stress or damage
for terrestrial systems should be broadened
and intensified.
          Eric Goodman. Matt Zabik, Jeffrey J. Jenkins, Robert M. Kon, and Renate M.
            Snider are with Michigan State University, East Lansing, Ml.
          Jay D. Gile is the EPA Project Officer (see below).
          The complete report consists of two parts,  entitled "Ecosystem Responses to
           Alternative Pesticides in the Terrestrial Environment:"
             "A System Approach." (Order No. PB 84-162 726; Cost: $25.00)
             "POEM Source  Program,  Sample  Data, Sample Runs (Magnetic Tape,"
             (Order No. PB 84-162 734; Cost: $790.00)
          The above report and magnetic tape will be available only from: (cost subject to
                 National Technical Information  Service
                 5285 Port Royal Road
                 Springfield, VA22161
                 Telephone: 703-487-4650
          The EPA Project Officer can be contacted at:
                 Environmental Research Laboratory
                 U.S. Environmental Protection Agency
                 Corvallis, OR 97333
                                                                                 U.S. GOVERNMENT PRINTING OFFICE; 1984—759-015/7626
United States
Environmental Protection
Center for Environmental Research
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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