United States
Environmental Protection
Agency
Chesapeake Bay
Program
Annapolis MD 21403
Research and Development
EPA-600/S3-83-078 Nov. 1983
Project Summary
Ware River Intensive Watershed
Study
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
estuary.
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).
-------
Introduction
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
basin.
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
ditches.
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
site.
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/Conclusions
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.
Recommendations
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
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use S300
-------
United States
Environmental Protection
Agency
Environmental Research
Laboratory
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).
Introduction
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
attacked.
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.
Description
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.
Recommendations
(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
change)
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
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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