AQUA TERRA Consultants
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Development of BASINS Modeling System Version 3

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

The U.S. Environmental Protection Agency's water programs and their counterparts in states and pollution control agencies are increasingly emphasizing watershed and water quality-based assessment and integrated analysis of point and nonpoint sources. Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) is a system developed to meet the needs of such agencies. It integrates a geographic information system (GIS), national watershed data, and state-of-the-art environmental assessment and modeling tools into one convenient package.

Originally released in September 1996, BASINS addresses three objectives: (1) to facilitate examination of environmental information, (2) to provide an integrated watershed and modeling framework, and (3) to support analysis of point and nonpoint source management alternatives. It supports the development of total maximum daily loads (TMDLs), which require a watershed-based approach that integrates both point and nonpoint sources. BASINS can support the analysis of a variety of pollutants at multiple scales, using tools that range from simple to sophisticated.

For the past three years AQUA TERRA Consultants has served as the prime contractor for development and support of BASINS. The development activities that have been undertaken to migrate from BASINS 2.0 to BASINS 3.0 during this time have focused as much on ancillary software as on enhancement of the core modeling system itself. Accordingly, the BASINS 3.0 installation program installs not only the core system but also WinHSPF, GenScn, WDMUtil, and PLOAD, the first three of which were developed exclusively by AQUA TERRA Consultants. WinHSPF is a new interface to HSPF Version 12 that is replacing NPSM from BASINS 2.0. GenScn is a model post processing and scenario analysis tool that is used to analyze output from HSPF and SWAT. WDMUtil is used to manage and create the watershed data management files (WDMs) that contain the meteorological data and other time series data used by HSPF. PLOAD is a GIS and spreadsheet tool that offers an alternative method for calculating nonpoint sources of pollution in watersheds.

BASINS 3.0 includes several new data and functions including 1-degree DEM grids, an automatic delineation tool that creates watershed boundaries based on DEM grids, and new watershed report function for land use, topography, and hydrologic response units. In addition, a new watershed model, the Soil and Water Assessment Tool (SWAT) has been added. SWAT is a watershed, scale model developed to predict the impact of land management practices on water, sediment, and agricultural chemical yields in large complex watersheds with varying soils, land use, and management conditions over long periods of time. In its role as prime contractor for BASINS support and development this past three years, AQUA TERRA has been closely involved in all the enhancements that were implemented within the core modeling system.

BASINS 3.0 also demonstrates an important change in the development philosophy of BASINS. BASINS 3.0 will be distributed as composed of a core system and several Arcview extensions. All BASINS data management utilities, assessment tools, report tools, and models were converted as extensions. This modular and open architecture offers numerous advantages both to the users and developers. For instance, the users may customize their BASINS project to only include extensions that are needed. Moreover, it will be easier for the developers to maintain and provide updates of the individual extensions because it will not involve changing and reissuing a patch or new version for the entire system. This makes it a lot easier for the users to upgrade their system. It also encourages users and other developers to develop extensions for BASINS. AQUA TERRA Consultants was responsible for the implementation of this new development philosophy; with the firm's recent award of a 5-year continuation in its BASINS support contract, AQUA TERRA will continue to direct the future of BASINS' development.

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