HSPF Application Assistance For The Patuxent River Nonpoint Source
Assessment Study and Development of a Watershed Model of
the Patuxent River Basin
Clients:
- State of Maryland, Department of Health
- Mental Hygiene, Office of Environmental Programs, Maryland Department of the Environment, Baltimore, MD
- U.S. Geological Survey, Office of Surface Water, Reston, VA
For more than a decade, AQUA TERRA principals
and staff have been providing watershed model development and
application assistance to government agencies charged with
evaluating nonpoint source pollution in the Patuxent River Basin.
Four contracts with the three agencies listed above have resulted
in AQUA TERRA providing nearly continual services that support
comprehensive watershed management.
In 1984 the Maryland Office of Environmental
Programs initiated a comprehensive, coordinated monitoring and
modeling program for the Patuxent River Basin to identify critical
regions of nonpoint source load generation, evaluate water quality
conditions resulting from both point and nonpoint source
contributions, and analyze the impact of alternative management
practices and land use policies. The HSPF model was selected to
provide the framework for the program, and we were selected to
provide expert assistance in model use and application throughout
the 7-year project.
Our scope of activities included: review and
analysis of available data for model application; assistance in
site selection and design of the monitoring program; development
of a simulation plan; training in HSPF operations, calibration,
verification, and interpretation of model results; direct
assistance and participation in the model calibration and
verification for both water quantity and quality; and guidance in
model use for analysis of alternative management practices and
land use conditions.
In 1986, the USGS Watershed Data Management
System (WDMS) was selected as the modeling data management tool
for the project, and the development of a Patuxent River Watershed
Data base Management (WDM) file was initiated to include all the
meteorologic, hydrologic, water quality, and land use information
needed for the HSPF application. Under a separate contract with
the USGS, AQUA TERRA implemented the HSPF/WDM linkage which allows
HSPF to directly use WDM files during model operation. The
HSPF/WDM linkage has subsequently been tested and used in the
hydrologic calibration of subwatersheds within the Patuxent River
Basin.
Since 1986, the Maryland Department of the
Environment has undertaken a comprehensive monitoring and modeling
program of the Patuxent River basin. The principal objective of
this program is the development of a tool that will permit
identification of critical regions of nonpoint source pollution in
the basin, evaluation of the effectiveness of corrective measures
in reducing water quality impacts, and prediction of the water
quality impacts of various land use policies. This project
involved a cooperative effort sponsored by the State of Maryland,
with the assistance of the U.S. Geological Survey, to develop a
calibrated model of the Patuxent River basin using the
Hydrological Simulation Program - FORTRAN (HSPF). The resulting
Patuxent River Basin Model is a finer scale version of the
Patuxent portion of the EPA's Chesapeake Bay Watershed Model; the
basin and the river are represented by 21 land segments and 34
stream/reservoir reaches. Land uses simulated in each segment
include forest, four residential/urban categories, eight crop
categories, and pasture. The model simulates hydrological and
nutrient processes on the land surface and soil profile as well as
in streams, rivers, and reservoirs. Inputs to the instream model
include the nonpoint loadings generated by the land model, point
sources, atmospheric deposition, and water supply diversions.
The project also demonstrated several
innovative software tools designed to facilitate watershed
modeling. Development of the Patuxent model involved the use of
the following modern computational techniques: model segmentation,
land use, and soils-related parameters were developed from a
Geographic Information System; the hydrology calibration was
performed using an "Expert Advisor" program designed for HSPF by
the U.S. Geological Survey; and the model is operated by an
interactive graphical interface ("Scenario Generator") that
facilitates simulation of the calibrated model to represent a
range of scenarios. The interface includes a map of the basin and
capabilities to modify the model inputs, execute the model, and
display results.
AQUA TERRA directed the basin segmentation,
assembled the model database, performed the hydrology calibration,
developed the AGCHEM model of the cropland areas, performed
sediment and water quality calibration, and completed nutrient
management and forest scenario runs. AQUA TERRA also developed the
Scenario Generator interactive interface.
