United States
 Environmental Protection
 Agency
 Environmental Research
 Laboratory
 Athens GA 30601
 Research and Development
 EPA-600/S3-83-069  Nov. 1983
 Project Summary
Application  of Hydrologic
 Simulation  Program-FORTRAN
 (HSPF)  in  Iowa  Agricultural
 Watersheds
Anthony S. Donigian, Jr., John C. Imhoff, Brian R. Bicknell,
James L. Baker, Douglas A. Haith, and Michael F. Walter
  The Hydrologic Simulation Program-
FORTRAN (HSPF) was applied to two
watersheds in Iowa to test the model's
capability in evaluating  the effects of
agricultural best management practices
(BMPs) on water quality. The project
first involved refining HSPF to incorporate
a pesticide risk assessment methodology.
Before the application of HSPF to the
Four Mile Creek Watershed, an evaluation
of the sensitivity of model parameters
for BM Ps was done and a parameter esti-
mation manual was prepared. The model
was calibrated and verified in the
watershed. The water quality effective-
ness of alternative BMP  scenarios was
then evaluated using the parameter
estimation manual. To evaluate the
ease of model scale-up and extrapolation
to a larger basin, the model was then
applied to the Iowa River Basin above
Coralville Reservoir.
  These applications of HSPF in water-
sheds of different size in Iowa demon-
strated that HSPF is a flexible and
realistic means of approximating the
impacts of candidate BMPs on water
quality in  small watersheds and large
river basins. Moreover, risk assessment
procedures  can  be  used  with the
simulated chemical concentration time
series produced by the model to
evaluate  the impacts  on selected
aquatic organisms.
  True verification of  any model's
ability to simulate the effects of BMPs,
however, must await the availability of
both pre- and post-BMP implementation
data. Until such data have beeV) collected,
model? such as HSPF can still be used
to approximate the effects of BMPs on
stream water quality,7and  sensitivity
analyses  of various model parameters
can assist  the BMP evaluation and
planning  process.
  These applications provide one of the
first systematic attempts to combine a
detailed  simulation  of agricultural
runoff and soil processes, which calcu-
late surface and subsurface pollutant
transport to receiving waters, with sub-
sequent simulation of instream trans-
port and transformations. The result is a
comprehensive simulation  of water-
shed hydrology and water quality.
  This Project Summary was developed
by EPA's Environmental Research
Laboratory.  Athens. GA, to announce
key findings of the research project that
is fully documented in three separate
reports (see Project Report ordering
information at back).

Background
  HSPF is a  comprehensive program for
modeling sediment, pesticides, nutrients,
and other water quality constituents in
runoff from urban, agricultural, and other
lands. The model allows detailed simula-
tion of stream hydraulics, water quality
processes, pesticide and nutrient be-
havior in soil, and sediment-contaminant
transport. Extensive data handling and
analysis procedures that support and
complement the simulation capabilities
are included.

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  A unique feature of HSPF is the incor-
poration of runoff models—the Agri-
cultural Runoff Management (ARM)
Model  and the Nonpoint Source (NFS)
Model  and stream transport and fate
models-in a systematic framework. Sim-
ply put, the model uses information on
meteorology,  land  use, and  agronomic
characteristics to simulate a time history
of the quantity and quality of the runoff.
Flow rate, sediment load,  and nutrient
and pesticide concentrations are pre-
dicted. The model  then takes these  re-
sults and information about the stream
channels in the watershed and simulates
the processes that  occur  in these
streams. This produces a time history of
water quantity and quality at any point in
the watershed. HSPF can be applied to a
wide range of water resource problems.
The key attribute that makes it widely ap-
plicable is its  ability to simulate the con-
tinuous behavior of time-varying physical
processes and to provide statistical sum-
maries of the results.
  The work reported here was performed
as part of a comprehensive field evalua-
tion program  in two Iowa watersheds
(Figure  1). The purposes of the program
were to test and demonstrate (1) the ca-
pability of agricultural BMPs to achieve
water quality goals, and (2) the applicabil-
ity of water quality planning tools (such as
HSPF) to the BMP evaluation and selec-
tion process.  Program results are de-
scribed in "HSPF Parameter Adjustments
to Evaluate the Effects of Best Manage-
ment Practices," "Modeling Water Quali-
ty and the Effects of Agricultural Best
Management Practices  in  Four  Mile
Creek, Iowa," and "Preliminary Applica-
tion of HSPF  to the Iowa  River Basin to
Model  Water Quality and the Effects of
Agricultural  Best Management Prac-
tices."

HSPF  Parameter
Adjustments for
Evaluating  BMPs
  A key problem  in  applying most
models, especially those with an empirical
basis, is how to adjust model parameters
to represent  the effects of a specific
practice, or combination of practices, that
comprise  a BMP or system of BMPs.
"HSPF Parameter Adjustments to Evaluate
the Effects of Agricultural Best Manage-
ment  Practices" qualitatively assesses
the effects  of selected  agricultural
practices on runoff, erosion, and chemical
processes, and quantifies the associated
adjustments to model parameters based
on the current state of science. Although
the specific  parameter changes are
                                                                Iowa
                                                                Cedar Rivers
                                                      I	Z>>  Basin
                                              Coralville
                                              Reservoir!? lowa
                                                        City
Figure 1.    Location of Four Mile Creek and Iowa-Cedar River Basin Sites for lowa Field
           Evaluation Program.
particular to the HSPF and ARM models,
the information  presented  is generally
applicable and should  be pertinent to
many models having similar representa-
tions of the relevant processes.
  In summary, the report discusses the
technical aspects of conventional practices
and candidate BMPs  as a  basis for
predicting BMP  impacts on relevant
agricultural runoff processes in lowa
watersheds. Guidelines and recommen-
dations are included for adjusting all
major parameters whose effects can be
reasonably  quantified. Deficiencies in
the current  state of knowledge of BMP
effects and recommendations for future
research and model  improvements are
presented and discussed.
  The approach to assessing the manner
in which HSPF  parameters should be
adjusted to  represent the effects of
candidate BMPs involved six steps:
 • Define  conventional  agricultural
   practices for lowa watersheds.
 • Select and define candidate BMPs.
 • Evaluate qualitatively the  impact of
   each  candidate BMP on agricultural
   runoff processes (quantity and quality)

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   relative to conventional practices.
 • Identify HSPF model parameters that
   control or  affect specific  runoff
   processes (quantity and quality).
 • Evaluate  qualitatively the relative
   effect of each candidate BMP on the
   HSPF  model parameters identified
   above.
 • Quantify the effects of the candidate
   BMPs on the identified model param-
   eters based on available data, current
   literature, and,  lacking all else, best
   judgment  or experience.

The qualitative assessments provided the
basis for quantifying the changes  in
model parameters.
  The qualitative assessment of how the
candidate BMPs could be represented by
the indicated changes in HSPF parameters
relative to those for conventional practices
is presented in the report. The candidate
BMPs  are divided into  nonstructural,
structural, and  input management prac-
tices.
  Finally, the report provides a discussion
of the major  HSPF runoff, sediment and
chemical parameters in terms of adjust-
ments or changes needed to simulate the
effects of the candidate BMPs.

Modeling BMP Effects-
Four Mile Creek
  "Modeling Water Quality and the
Effects of Agricultural Best Management
Practices in  Four Mile  Creek,  Iowa"
discusses the calibration and verification
of HSPF in a  relatively small watershed
(approximately 20  sq. mi.).  Such efforts
are needed to evaluate model capabilities
and develop sufficient confidence so that
the model can be used for BMP analyses.
  Hydrologic calibration involves iterative
adjustments in  selected  parameter
values based on comparison of observed
and simulated runoff volumes and storm
hydrographs.  The model  representation
and  calibrated parameters are then
verified by performing the same compari-
sons on  an  independent data set, i.e.,
runoff volumes and hydrographs that
were not  used  in the calibration. In the
Four Mile Creek watershed, observed
runoff data for calibration  and verification
were available for three watershed sites
and three small  field sites. Approximately
7  years  of daily  streamflow data (and
selected hydrographs) were available for
the watershed sites,  and 2  1/2 years of
runoff data were available from the field
sites. A summary  of the annual  runoff
and  daily flow  statistics  for calibration
and  verification at the  Traer gage,  a
watershed site on Four Mile Creek is
given in the report. The calibration and
verification results of modeling the
watershed hydrology compare reasonably
well with the observed values.
  The calibration and verification results
of modeling alachlor concentrations are
shown in Figure 2. The relative timing of
applications and  the first  significant
storm event have a major impact on the
resulting chemical runoff.  Although the
alachlor simulations are generally higher
than observed values, the concentrations
and loads are generally within the range
of the observed values. Oftentimes,
major discrepancies can be explained by
the absence of, or large errors contained
in, sampling data during storm events.
  The  simulations of alachlor edge-of-
field loadings and stream concentrations
showed that approximately 30% of the
alachlor reaching the  stream did not
reach the watershed outlet at Traer. This

            Calibration
is likely due to adsorption onto sediment
particles, resulting deposition in the bed,
and  decay of the compound in the
channel bed.
  Another method of viewing calibration
and verification results is to determine
whether decisions on risk or exposure to
aquatic organisms would be different  if
the analyst based his decision on the
simulated or the observed chemical
information. Figure 3 demonstrates how
the frequency (percent of time) of acute,
chronic, and sub-lethal conditions might
be determined for a particular stream
given a time series of chemical concentra-
tions. Using the risk assessment meth-
odology integrated into HSPF,  the ob-
served and simulated chemical concen-
trations were analyzed to determine the
percent of time  conditions within  each
region shown in Figure 3 would exist. The
results of this analysis using a hypothetical
•c
\
Oi
c
•3

Figure 2.    Calibration and verification results for solution alachlor loading at Traer, IA.

                                         3

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 a
                                 Sublethal Region
                                    Duration
Figure 3.   Lethality analysis of chemical concentration data.
organism are  shown  in Table 1.  A
hypothetical organism was used because
all  the  values observed for  alachlor
concentrations were  considerably lower
than any  of  the  maximum  acceptable
toxicant concentration  values  for all
species of fish found  in Four Mile Creek.
The table  shows that the observed and
simulated values  agree quite closely
indicating  that the ultimate decision on
aquatic risk and exposure would be the
same whether the observed or simulated
values were used.
  In summary, the  instream  pesticide
simulation results show that reasonably
good simulations  can be obtained by
using small  site  parameter values for
alachlor in conjunction  with hydrologic
parameters  calibrated on  the entire
watershed and a reasonably good instream
hydraulic and sediment transport simula-
tion. In effect, the work has shown that an
adequate  simulation of the hydrologic
transport  components on a watershed
basis provides a viable means of simulat-
ing chemical  transport and aquatic risk.
  The nutrient  simulation followed the
same general procedures as the pesticide
simulation.  The nutrient parameters
calibrated on  the  small  sites were
extrapolated to the entire watershed and
used in conjunction with the watershed
hydrology and  stream hydraulics to
simulate  nutrient concentrations and
loadings at the watershed outlet. Unlike
the  pesticide simulation,  nutrients are
contributed  from  all land  within  the
watershed  whether or not the  land
received fertilizer applications.
  The daily concentrations and loads
from  nitrate,  ammonia, and  chloride
generally indicate that the loads are
simulated considerably better than
concentration values, but that the overall
simulation is reasonably good. The large
differences between  the simulated and
recorded values for ammonia and phos-
phate at the watershed outlet are likely
due to the lack of simulation data on in-
stream sediment and sediment-nutrient
interactions.  HSPF  did  not  simulate
sediment-nutrient  interactions  as  was
done for pesticides.
  Although the results were viewed as
preliminary, it was  concluded that the
model is capable of representing the
overall  watershed  system  behavior  in
terms of nutrient simulation. Additional
calibration efforts and the suggested
model enhancements would likely increase
significantly the agreement of simulated
and  observed  values and thus  improve
the preliminary results presented here.
  As a demonstration  of the  model's
utility, a BMP scenario  was evaluated
using the parameter values reported in
the previous study. Using the assumptions
and  associated changes in parameter
values for the BMP scenario described in
the report, a comparison can be made of
the simulated  base condition versus the
BMPscenario. Table 2 shows the average
percent reductions in runoff (8.3%),
sediment (41.7%), alachlor (for  solution
and sediment,  32.5% and 68.2%, respec-
tively), and nutrients (varies byform)tobe
expected from the BMP.
  Finally, Table 3 shows the results of the
simulation of the BMP scenario  in terms
of reductions in the fraction of time when
acute and lethal conditions exist, following
the lethality analysis methodology men-
tioned previously. The reductions indicate
an 8% reduction in the percentage of time
when  pesticides  exceeded the MATC
levels  in the  watershed. Although  the
values  listed  here  are  specific to  the
conditions under which this BMP scenario
was simulated, the overall methodology
and analysis indicates how the procedures
can  be used to evaluate the effects of
BMP scenarios on the resulting risk of
exposure of aquatic organisms to chemi-
cals.
  Although this study demonstrated the
overall  utility of  the HSPF model  for
evaluating BMPs, numerous weaknesses
and  difficulties were identified.  Needed
improvements include a better capability
to predict pesticide decay in the field
under various environmental conditions;
better understanding of nutrient param-
eters,  of tile  drainage  and snowmelt
effects and of field-to-stream sediment
delivery; and a better basis for assumptions
about agronomic practices.
Table 1.    Lethality Analysis for Alachlor in Four Mile Creek for Hypothetical Organism

                                            Global Exceedance
                                               (% of time)
1978
Calibration
DBS SIM
Acute Region
Above MATC Value
Sublethal Region
(below MATC)
0.5
4.4
95.6
3.3
6.6
93.4
1976
Verification
OBS SIM
0.5
3.3
96.7
1.9
8.1
91.9
1976-78
OBS SIM
0.2
1.5
98.5
1.2
3.2
96.8
MA TC - Maximum Acceptable Toxicant Concentration.
      (0.003 mg/l used above).
OBS  - Observed values.
SIM  - Simulated values.
                                   4

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Table 2.    Comparison of Base Conditions with BMP Scenario on Four Mile Creek


                                                    BMP Scenario    % Difference
           Base
         Conditions
Runoff (mm)
   76
   77
   78
   Total

Sediment (tonne/ha)
   76
   77
   78
   Total

Alachlor (kg/ha)
 Solution:
   76
   77
   78
   Total

 Sediment:
   76
   77
   78
   Total
            69.9
            48.8
           161.8
           280.5
           0.437
           0.042
           1.381
           1.860
        0.00166
        0.00009
        0.00212
        0.00387
        0.00012
              0
        0.00010
        0.00022
                        60.7
                        43.7
                       152.9
                       257.3
                       0.175
                       0.022
                       0.888
                       1.085
                     0.00084
                     0.00005
                     O.OO168
                     0.00261
                     0.00003
                           0
                     0.00004
                     0.00007
                           -13.2
                           -10.4
                           - 5.5
                           - 8.3
                            -60.0
                            -47.6
                            -35.7
                            -41.7
                            -49.4
                               0
                            -20.7
                            -32.5
                            -69.2
                               0
                            -60.0
                            -68.2
Nutrients fkg/ha): 1 1/77 - 10/78
N03
Cl
NH3-Sol
*NH3-Sed
*PO4-Sol
*PO4-Sed

26.2
34.0
2.18
0.00045
1.69
0.00029

20.2
30.1
0.69
0.00019
1.14
0.00018

-22.9
-11.5
-68.3
-57.8
-32.5
-37.9
  - Edge of Stream Loadings.
Table 3.    Lethality Analysis of BMP Scenario for Alachlor in Four Mile Creek for Hypothetical
            Organism

                                          Global Exceedance
                                             (% of time)
Base Conditions

Acute Region
Above MA TC Value
MAX
1.2
3.2
AVER
0.4
2.5
BMP Scenario
MAX
1.2
2.9
AVER
0.2
2.3
% Change
MAX
0.0
-9.4
AVER
-50.
-8.0
Sublethal Region
 (below MA TC)
96.8
97.5
97.1
                    97.7
+0.3
                           +0.2
MA TC - Maximum Acceptable Toxicant Concentration
       (0.003 mg/l used above).
MAX - Daily maximum concentrations.
A VER - Daily average concentrations.
HSPF Demonstration -
Iowa River Basin
  "Preliminary Application of HSPF to the
Iowa River Basin to Model Water Quality
and  the  Effects of Agricultural  Best
Management Practices" describes a
basin-scale model application that com-
bines the detailed simulation of agricul-
tural runoff and soil processes, surface
and  subsurface pollutant transport to
                receiving waters, and subsequent simula-
                tion of instream transport and trans-
                formations. The result is a comprehensive
                simulation of river  basin  water quality.
                Comparisons of water quality  resulting
                from conventional  agronomic  practices
                and BMPs provide a basis for determining
                the net effects and associated benefits of
                BMP implementation. Furthermore,
                using simulated concentrations of pesti-
                cides  and  other toxic  pollutants in
conjunction with lethality-duration in-
formation,  the  frequency of  acute and
chronic toxic conditions can be determined
to assess  the risk  to  aquatic life of
proposed practices.
  The  investigation  of  the  Iowa River
Basin (approximately 7240 sq. km. reported
here is an  extension or scale-up of the
modeling study in the Four Mile Creek
watershed (approximately 52  sq. km.)
described previously. The objective was
to extrapolate the methodology developed
on Four  Mile Creek to  the  Iowa River
Basin to demonstrate its applicability and
functionality on a large  river basin. This
demonstration must be viewed as prelimi-
nary due to the limited data and project
resources.
  The report documents the procedures
and assumptions used in applying HSPF
to the Iowa River Basin. The  simulation
results presented are indicative of the
type of  information  produced by  the
model. The specific results and compari-
sons with observed data should not be
used as a final* determination of  the
accuracy or reliability of HSPF, however,
because of the preliminary nature of this
work.  Moreover, the  model  results
should not be used as a basisfor planning
decisions on agricultural nonpoint pollu-
tion and BMPs in the study area without
additional  calibration efforts  and re-
evaluation of the underlying assumptions
on which this demonstration  rests. This
investigation was directed to the assess-
ment of operational problems of modeling
chemical fate and transport at the river
basin scale.
  The development of a simulation plan
involved four steps: characterize the area
with regard to  meteorologic conditions,
soils, topography, land use, pollutant
sources, etc.; segment the basin  to define
areas of homogenous hydrologic response;
evaluate  streamflow and water quality
data to devise a modeling and calibration
scheme; and  ascertain the  relative
importance of various pollutant  sources.
  Prior to actual HSPF application to the
entire  basin,  a limited calibration of
hydrology and  water quality was con-
ducted to demonstrate sufficient agree-
ment between model results and available
data so that the model could then be used
for BMP analysis and evaluation.
  For the actual demonstration of HSPF,
a BMP scenario similar to that exercised
on the Four Mile Creek watershed, was
evaluated on the Iowa River  Basin, i.e.,
conservation tillage  plus contouring.
Table 4 shows a comparison of  loadings
in the Iowa River at Marengo for the 5-
year simulated base conditions and BMP
evaluations. Average percentage reduc-

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Table 4.
Comparison of Loadings in the Iowa River at Marengo for Base Conditions and BMP
 Simulations
                      Year
                         Base
BMP
% Difference
RUNOFF (mm)





SEDIMENT
(tonnes/ha)




SOLN. ALACHLOR
(kg/ha)




SED. ALACHLOR
(kg/ha)




NITRATE N
(kg/ha)




AMMONIA N
(kg/ha)




1974
1975
1976
1977
1978
A verage
1974
1975
1976
1977
1978
Average
1974
1975
1976
1977
1978
A verage
1974
1975
1976
1977
1978
Average
1974
1975
1976
1977
1978
A verage
1974
1975
1976
1977
1978
Average
183.0
124.0
80.0
47.8
299.0
147.0
3.91
0.88
0.56
0.019
5.69
2.21
0.0278
0.0026
0.0008
0.00
0.0068
0.0076
0.0032
0.0002
0.00
0.00
0.0007
0.0008
31.0
14.9
9.5
4.9
18.5
15.8
0.48
0.57
0.53
0.37
0.91
0.57
170.0
116.0
73.9
42.4
280.0
136.0
2.62
0.47
0.12
0.012
5.49
1.74
0.0219
0.0017
0.0004
0.00
0.0048
0.0058
0.0020
0.0001
0.00
0.00
0.0004
0.0005
29.8
9.5
6.2
3.0
13.1
12.3
0.41
0.30
0.20
0.09
0.46
0.29
-7.1
-6.4
-7.6
-11.3
-6.4
-7.5
-33.0
-47.0
-79.0
-37.0
-3.5
-21.0
-21.0
-35.0
-50.0
.
-29.0
-24.0
-38.0
-50.0
-
.
-43.0
-38.0
-3.9
-36.0
-35.0
-39.0
-29.0
-22.0
-15.0
-47.0
-62.0
-76.0
-49.0
-49.0
lions are approximated for runoff (7.5%),
sediment (21.0%),  alachlor (24% and
38% for solution and sediment, respec-
tively), nitrate (22%) and ammonia (49%).
  The  sediment  loss  reductions are
somewhat  less than expected. This is
likely due to the fact that a significant
portion  of the total sediment loss is
derived from the channel system itself,
which would not be significantly affected
by the BMPs.  The zero reductions in
alachlor occurred during years of extreme
drought.  The reductions for  nitrate and
ammonia were  lowest in the first year of
the simulation  period  due to the same
initial nutrient  storages in the soil for
both the base conditions and the BMP.
  As in the Four Mile Creek application,
one of the possible uses of  continuous
modeling of chemical fate and transport
is to evaluate  the  risk of exposure of
aquatic organisms to various magnitudes
and durations of chemical concentrations.
                                         1978 were not sufficient to reduce the
                                         concentrations below the 30 ppb thresh-
                                         old assumed in this risk analysis. Overall,
                                         the reductions indicate a 23% reduction
                                         in the percent of time when lethal condi-
                                         tions occurred in the watershed.
                                           Specific  conclusions from  this study
                                         are:

                                         1. HSPF can  be used to model the flow,
                                            sediment, and water quality from
                                            large agricultural river basins.
                                         2. Many model parameters, primarily
                                            these related to hydrology and sedi-
                                            ment, are  calibration dependent.
                                         3. Meteorologic data for different por-
                                            tions of the basin  are  a critical
                                            component.
                                         4. With only  minimal calibration effort,
                                            simulation of flow frequencies on the
                                            main stem of the Iowa River was fair
                                            to good in this  study.
                                         5. Sediment  simulation  was  judged to
                                            be  fair to poor due  to  insufficient
                                            calibration, lack of data, and model
                                            deficiencies.
                                         6. Simulated pesticide  (i.e., alachlor)
                                            loadings and concentrations were in
                                            the expected range, asgenerally were
                                            the  simulated  nitrate-nitrogen and
                                            ammonia-nitrogen concentrations.

                                           Several needed improvements to HSPF
                                         were identified in this study:

                                         1. Accommodation  of  nutrient and
                                            chemical inputs with precipitation.
                                         2. Simulation of both ionized and un-
                                            ionized forms of ammonia  and sedi-
                                            ment-ammonia interactions.
                                         3. Better definition of bed water quality
                                            and  sediment processes, possibly
Table 5  shows  the  reductions  in  the        with a layered representation.
fraction of time  when acute and lethal     4. Use of output of nutrient transforma-
conditions  exist  under the simulated        tions as  aids  in calibration and
BMP scenario. It is interesting to note        analysis of model results.
that although the BMP scenario provided
substantial reductions  in the peak
concentrations (ranging from 9% to 41 %),
the absolute reductions  in 1974 and

Table 5.   Lethality Analysis of BMP Scenario for Alachlor in the Iowa River at Marengo, Iowa
                                                       Base Conditions
                                Global Exceedance
                                   (% of time)

                                     BMP Scenario
                                           i Change
                              Acute Region

                              Above MATC Value

                              Sublethal Region
                               (below MATC)
                    0.49

                    3.50

                   96.50
                          0.49

                          2.68

                         97.32
                                                                       0

                                                                     -23.4

                                                                     - 0.8
                              MA TC - Maximum Acceptable Toxicant Concentration
                                    (0.003 mg/l used above).

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AnthonyS. Donigian. Jr., John C. Imhoff, andBrianR. Bicknellare with Anderson-
  Nichols and Co.. Palo Alto. CA 94304; James L.  Baker is with Iowa State
  University, Ames, IA 500 J1; Douglas A. Haith and Michael F. Walter are with
  Cornell University, Ithaca, NY 14853.
T. O. Barnwell, Jr., is the EPA Project Officer (see below).
This Project Summary covers three reports, entitled:
  "HSPF Parameter Adjustments to Evaluate the Effects of Agricultural Best
    Management Practices,"(Order No. PB 83-247 171; Cost: $13.00)
    "Modeling Water Quality and the Effects of Agricultural Best Management
    Practices in Four Mile Creek, Iowa," (Order No. PB 83-250 183; Cost: $ 13.00)
    "Preliminary Application of HSPF to the Iowa River Basin to Model Water
    Quality and the Effects of Agricultural Best Management Practices," (Order
    No. PB 83-250 399; Cost: $13.001
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:
       Environmental Research Laboratory
       U.S. Environmental Protection Agency
       College Station Road
       Athens, GA 30613

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