AQUA TERRA Consultants
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Development of WinHSPF - An Independent, Fully Integrated Component of a Comprehensive Modeling System

Client: U.S. EPA Office of Science and Technology, Washington, DC

WinHSPF, an interface to the Hydrological Simulation Program - Fortran (HSPF), is a key component of Better Assessment Science Integrating point and Nonpoint Sources (BASINS) Version 3.0. BASINS 3.0 is being developed for the U.S. Environmental Protection Agency's Office of Water to respond to the continued needs of various agencies to perform watershed and water quality assessments integrating point and nonpoint sources. In particular, BASINS supports the development of Total Maximum Daily Loads (TMDLs), required under section 303(d) of the 1972 Clean Water Act for impaired waters.

Recognizing the need to estimate nonpoint source (NPS) loadings under various environmental conditions, and to combine them with measured or permitted point source (PS) loadings, a watershed modeling system with appropriate databases was integrated with a GIS platform operating on desktop PCs. A continuous simulation model was considered to be an ideal choice for a realistic representation of watershed processes. Continuous simulation models combine daily (or other time-step) measurements or synthesized estimates of effluent flows and loads, wet-weather source concentrations and loads, and receiving water flows to calculate receiving water concentrations; a deterministic model applied to time series of these variables will predict concentrations in chronological order in the same time sequence as the input variables.

HSPF is a proven, tested continuous simulation watershed model. It is one of the models recommended by the U.S. EPA for complex TMDL studies. Being a batch program, the HSPF model itself has no interactive user interface. Many user interfaces have been developed for HSPF that make the model easier to use, such as NPSM (contained within BASINS 2.0), and the GenScn scenario generating software. WinHSPF builds upon the successes of predecessor HSPF interfaces, but the design of WinHSPF provides the user greater flexibility, with more advanced interactive capabilities.

WinHSPF is completely independent of the BASINS system and can be run stand-alone. At the same time it is a fully-integrated component of the BASINS system. This system architecture allows the user to choose the system environment that best suits his/her needs. This design also allows a programmer to enhance WinHSPF separately from the core BASINS system and from the model algorithms.

Internally, WinHSPF uses an object-oriented data structure linked to the HSPF model. WinHSPF works in such close conjunction with HSPF that all features of HSPF are available in WinHSPF. The object-oriented structure of WinHSPF allows for easy development of graphical interface tools to view simulation elements. These graphical tools help the user develop a deeper understanding of the assumptions and abstractions inherent in watershed modeling.

WinHSPF is currently distributed with BASINS.
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