                                                           File: ABSTRACT.TXT


                        HSPF Model System Abstract


               Center for Exposure Assessment Modeling (CEAM)
     National Exposure Research Laboratory - Ecosystems Research Division
                  Office of Research and Development (ORD)
               U.S. Environmental Protection Agency (U.S. EPA)
                          960 College Station Road
                         Athens, Georgia 30605-2700

                                706/355-8400



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                                  Summary

Hydrological Simulation Program - FORTRAN (HSPF) is a comprehensive package
for simulation of watershed hydrology and water quality for both conventional
and toxic organic pollutants (1,2).  This model can simulate the hydrologic,
and associated water quality, processes on pervious and impervious land
surfaces and in streams and well-mixed impoundments.  HSPF incorporates the
watershed-scale ARM and NPS models into a basin-scale analysis framework that
includes fate and transport in one-dimensional stream channels.  It is the
only comprehensive model of watershed hydrology and water quality that allows
the integrated simulation of land and soil contaminant runoff processes with
in-stream hydraulic and sediment-chemical interactions.

The manual discusses the structure of the system, and presents a detailed
discussion of the algorithms used to simulate various water quantity and quality
processes.  It also contains all of the information necessary to develop input
files for applying the program, including descriptions of program options,
parameter definitions, and detailed input formatting data.

The result of this simulation is a time history of the runoff flow rate,
sediment load, and nutrient and pesticide concentrations, along with a time
history of water quantity and quality at any point in a watershed.  HSPF
simulates three sediment types (sand, silt, and clay) in addition to a single
organic chemical and transformation products of that chemical.  The transfer
and reaction processes included are hydrolysis, oxidation, photolysis,
biodegradation, volatilization, and sorption.  Sorption is modeled as a
first-order kinetic process in which the user must specify a desorption rate
and an equilibrium partition coefficient for each of the three solids types.

Resuspension and settling of silts and clays (cohesive solids) are defined in
terms of shear stress at the sediment water interface.  The capacity of the
system to transport sand at a particular flow is calculated and resuspension
or settling is defined by the difference between the sand in suspension and
the transport capacity.  Calibration of the model requires data for each of
the three solids types.  Benthic exchange is modeled as sorption/desorption
and deposition/scour with surficial benthic sediments.  Underlying sediment
and pore water are not modeled.

                                Documentation

The original version of this report was submitted in fulfillment of Grant No.
R804971-01 by Hydrocomp, Inc., under the sponsorship of the U.S.
Environmental Protection Agency.  That work was completed in January 1980.
 
Extensive revisions, modifications, and corrections to the original report
and the HSPF code were performed by Anderson-Nichols and Co. under Contract
No. 68-03-2895, also sponsored by the U.S. EPA.  That work was completed in
January 1981.  Versions 7 and 8 of HSPF and the corresponding documents were
prepared by Linsley, Kraeger Associates, Ltd. and Anderson-Nichols under
Contract No. 68-01-6207, the HSPF maintenance and user support activities
directed by the U.S. EPA laboratory in Athens, GA. 

The HSPF User's Manual for Versions 10 and 11 were prepared by AQUA TERRA
Consultants of Mountain View, CA, incorporating code modifications
corrections, and documentation of algorithm enhancements sponsored by the
U.S. Geological Survey, the U.S. EPA Chesapeake Bay Program, the U.S. Army
Corps of Engineers, and the U.S. EPA Athens Environmental Research
Laboratory.  The version 11 manual and code were prepared under sponsorship
of the U.S. Geological Survey under Contract No. 14-08-0001-23472.

The HSPF User's Manual is available as a WordPerfect (version 5.1) document
in (binary, non-ASCII) files HSPF_V11.001, HSPF_V11.002, HSPF_V11.003,
HSPF_V11.004, HSPF_V11.005, HSPF_V11.006, and HSPF_V11.007 in the DOCUMENT
sub-directory.  Refer to file READ.ME in the README sub-directory for further
information on the storage format and printing requirements of the user's
manual files.

                             Data Requirements

Data needs for HSPF can be extensive.  HSPF is a continuous simulation
program and requires continuous data to drive the simulations.  At a minimum,
continuous rainfall records are required to drive the runoff model and
additional records of evapotranspiration, temperature, and solar intensity
are desirable.  A large number of model parameters can be specified although
default values are provided where reasonable values are available.  HSPF is
a general-purpose program and special attention has been paid to cases where
input parameters are omitted.  In addition, option flags allow bypassing of
whole sections of the program where data are not available.

                                  Output

HSPF produces a time history of the runoff flow rate, sediment load, and
nutrient and pesticide concentrations, along with a time history of water
quantity and quality at any point in a watershed.  Simulation results can be
processed through a frequency and duration analysis routine that produces
output compatible with conventional toxicological measures (e.g., 96-hour
LC50).

                        Assumptions and Limitations

HSPF assumes that the "Stanford Watershed Model" hydrologic model is
appropriate for the area being modeled.  Further, the instream model assumes
the receiving water body is well-mixed with width and depth and is thus
limited to well-mixed rivers and reservoirs.  Application of this methodology
generally requires a team effort because of its comprehensive nature.

                            Application History

HSPF and the earlier models from which it was developed have been extensively
applied in a wide variety of hydrologic and water quality studies (3,4),
including pesticide runoff model testing (5), aquatic fate and transport
model testing (6,7), and analyses of agricultural best management practices
(8,9).  An application of HSPF in a screening methodology for pesticide
review is described by Donigian et al. (10).  In addition, HSPF has been
validated with both field data and model experiments, and has been reviewed
by independent experts (11-20).

The Stream Transport and Agricultural Runoff for Exposure Assessment
Methodology (STREAM) applies the HSPF program to various test watersheds for
five major crops in four agricultural regions in the United States,
defines a "representative" watershed based on regional conditions and an
extrapolation of the calibration for the test watershed, and performs a
sensitivity analysis on key pesticide parameters to generate cumulative
frequency distributions of pesticide loads and concentrations in each
regions.  The resulting methodology requires the user to evaluate only the
crops and regions of interest, the pesticide application rate, and three
pesticide parameters -- the partition coefficient, the soil/sediment decay
rate, and the solution decay rate.

The EPA Chesapeake Bay Program has been using the HSPF model as the framework
for modeling total watershed contributions of flow, sediment, and nutrients
(and associated constituents such as water temperature, DO, BOD, etc.) to the
tidal region of the Chesapeake Bay (21,22).  The watershed modeling
represents pollutant contributions from an area of more than 68,000 sq. mi.,
and provides the input to drive a fully dynamic three-dimensional,
hydrodynamic/water quality model of the Bay. The watershed drainage area is
divided into land segments and stream channel segments.  The land areas
modeled include forest, agricultural cropland (conventional and conservation
tillage systems), pasture, urban (pervious and impervious areas), and
uncontrolled animal waste contributions. The stream channel simulation
includes flow routing and oxygen and nutrient biochemical modeling (through
phytoplankton) in order to account for instream processes affecting nutrient
delivery to the Bay.

Currently, buildup/washoff type algorithms are being used for urban
impervious areas, potency factors for all pervious areas, and constant (or
seasonally variable) concentrations for all subsurface contributions and
animal waste components. Enhancements are underway to utilize the detailed
process (i.e. Agrichemical modules) simulation for cropland areas to better
represent the impacts of agricultural BMPs and to include nitrogen cycling in
forested systems to evaluate the impacts of atmospheric deposition of
nitrogen on Chesapeake Bay. The watershed modeling is being used to evaluate
nutrient management alternatives for attaining a 40% reduction in nutrient
loads delivered to the Bay, as defined in a joint agreement among the
governors of the member states.

                                 References

1.  Bicknell, B.R., J. C. Imhoff, J. L. Kittle, A. S. Donigian, and R.C.
Johanson.  1993.  Hydrological Simulation Program - FORTRAN (HSPF): Users
Manual for Release 10. EPA-600/R-93/174, U.S. EPA, Athens, GA, 30605.

2.  Donigian, A. S., J. C. Imhoff , B. R. Bicknell, and J. L. Kittle.  1984.
Application Guide for the Hydrologic Simulation Program - FORTRAN.
EPA 600/3-84-066, U.S. EPA, Athens, GA, 30605.

3.  Barnwell, T. O., and R. Johanson.  1981.  HSPF:  A Comprehensive Package
for Simulation of Watershed Hydrology and Water Quality.  In:  Nonpoint
Pollution Control: Tools and Techniques for the Future.  Interstate
Commission on the Potomac River Basin, Rockville, MD.

4.  Barnwell, T. O., and J. L. Kittle.  1984.  Hydrologic Simulation Program
- FORTRAN: Development, Maintenance and Applications.  In:  Proceedings Third
International Conference on Urban Storm Drainage.  Chalmers Institute of
Technology, Goteborg, Sweden.

5.  Lorber, M. N., and L. A. Mulkey.  1982.  An Evaluation of Three Pesticide
Runoff Loading Models.  J. Environ. Qual., 11:519-529.

6.  Mulkey, L. A., R. B. Ambrose, and T. O. Barnwell.  1986.  Aquatic Fate
and Transport Modeling Techniques for Predicting Environmental Exposure to
Organic Pesticides and Other Toxicants -- A Comparative Study.  In: Urban
Runoff Pollution.  Springer-Verlag, New York, NY.

7.  Schnoor, J. L., C. Sato, D. McKetchnie, and D. Sahoo.  1987.  Processes,
Coefficients, and Models for Simulating Toxic Organics and Heavy Metals in
Surface Waters. EPA/600/3-87/015, U.S. EPA, Athens, GA, 30605.

8.  Donigian, A. S., J. C. Imhoff, and B. R. Bicknell.  1983.  Modeling Water
Quality and the Effects of Best Management Practices in Four Mile Creek,
Iowa.  EPA/600/3-81-044, U.S. EPA, Athens, GA, 30605.

9.  Bicknell, B. R., A. S. Donigian and T. O. Barnwell.  1984.  Modeling
Water Quality and the Effects of Best Management Practices in the Iowa River
Basin.  J. Water Sci. Technol., 17:1141-1153.

10. Donigian, A. S., D. W. Meier and P. P. Jowise.  1986.  Stream Transport
and Agricultural Runoff for Exposure Assessment: A Methodology.
EPA/600/3-86-011, U.S. EPA, Athens, GA, 30605.

11. Moore, L.W., H. Matheny, T. Tyree, D. Sabatini and S.J. Klaine. 1988.
Agricultural Runoff Modeling in a Small West Tennessee Watershed.  J. Water
Poll. Control Federation., 60:242-249.

12. Chew, Y.C., L.W. Moore, and R.H. Smith.  1991.  Hydrologic Simulation of
Tennessee's North Reelfoot Creek Watershed.  J. Water Poll. Control
Federation.,  63:10-16.

13. Hicks, C.N., W.C. Huber, and J.P. Heaney.  1985.  Simulation of Possible
Effects of Deep Pumping on Surface Hydrology Using HSPF. In:  T.O. Barnwell,
Jr. (ed.) Proceedings of Stormwater and Water Quality Model User Group
Meeting.  EPA-600/9-85/016, U.S. EPA, Athens, GA, 30605.

14. Motta, D.J. and M.S. Cheng. 1987.  The Henson Creek Watershed Study.  In:
H.C. Torno (ed.) Proceedings of Stormwater and Water Quality Users Group
Meeting.  Charles Howard and Assoc., Victoria, BC, Canada.

15. Nichols, J.C. and M.P. Timpe. 1985. Use of HSPF to simulate Dynamics of
Phosphorus in Floodplain Wetlands over a Wide Range of Hydrologic Regimes.
In:  T.O. Barnwell, Jr. (ed.) Proceedings of Stormwater and Water Quality
Model Users Group Meeting.  EPA-600/9-85/016,  U.S. EPA, Athens, GA, 30605

16. Schueler, T.R. 1983. Seneca Creek Watershed Management Study, Final
Report, Volumes I and II. Metropolitan Washington Council of Governments,
Washington, DC.

17. Song, J.A., G.F. Rawl, W.R. Howard. 1983. Lake Manatee Watershed Water
Resources Evaluation using Hydrologic Simulation Program FORTRAN (HSPF).  In:
P. Beron and T. Barnwell (eds.) Colloque sur la Modelisation des Eaux
Pluviales. GREMU 83/03 Ecole Polytechnique de Montreal, Quebec, Canada.

18. Sullivan, M.P. and T.R. Schueler. 1982. The Piscataway Creek Watershed
Model: A Stormwater and Nonpoint Source Management Tool. In: Paul E. Wisner
(ed.) Proceedings Stormwater and Water Quality Management Modeling and SWMM
Users Group Meeting.  Univ. of Ottawa, Dept. Civil Engr., Ottawa, Ont.,
Canada.

19. Weatherbe, D.G. and Z. Novak. 1985. Development of Water Management
Strategy for the Humber River. In: E.M. James and W. James (eds.) Proceedings
Conference on Stormwater and Water Quality Management Modeling. Computational
Hydraulics Group, McMaster University, Hamilton, Ont., Canada.

20. Udhiri, S., M-S Cheng, and R.L. Powell. 1985. The Impact of Snow Addition
on Watershed Analysis Using HSPF.  In:  T.O. Barnwell, Jr. (ed.) Proceedings
of Stormwater and Water Quality Model Users Group Meeting. EPA-600/9-85/016,
U.S. EPA, Athens, GA, 30605.

21. Donigian, A.S., B.R. Bicknell and J.L. Kittle.  1986. Conversion of the
Chesapeake Bay Basin Model to HSPF Operation. Prepared by AQUA TERRA
Consultants for Computer Sciences Corporation, Annapolis, MD, and U.S.EPA
Chesapeake Bay Program, Annapolis, MD.

22. Donigian, A.S.,  B.R. Bicknell, L.C. Linker, J. Hannawald, C. Chang, and
R. Reynolds. 1990. Chesapeake Bay Program Watershed Model Application to
Calculate Bay Nutrient Loadings: Preliminary Phase I Findings and
Recommendations. Prepared by AQUA TERRA Consultants for U.S. EPA Chesapeake
Bay Program, Annapolis, MD.

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