AQUA TERRA Consultants
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Modeling Support for the Minnesota Pollution Control Agency

Client:Minnesota Pollution Control Agency (MPCA), St. Paul, MN

Since early in 2010, AQUA TERRA has been providing watershed modeling services using USEPA’s computer simulation code Hydrologic Simulation Program FORTRAN (HSPF) to support the Minnesota Pollution Control Agency (MPCA) Total Maximum Daily Load (TMDL) studies. The State’s watersheds feature a wide variety of geology, hydrology, land use and meteorology. These forcing functions result in an equally diverse range of impairments, with the most prevalent being related to bacteria, nutrients turbidity and mercury. The MPCA is developing hydrologic and water quality models at the 8-digit HUC level for all 81 major watersheds in the State to identify critical areas of interest in each watershed.

Figure 1: Major Basins in Minnesota

MPCA has secured the support of AQUA TERRA and other firms to 1) identify critical areas related to sources/sinks and migration of contaminants in each of the 81 watersheds; 2) design a uniform HSPF modeling approach for implementation in each of these watersheds; and 3) develop and provide easy access to a corresponding set of model parameter values that will serve as a starting point for developing model applications.

To date, AQUA TERRA's support to MPCA has involved development of 1) a guidance document that summarizes the minimal elements that should be incorporated into any HSPF model application for the purpose of supporting the MPCA’s programmatic activities; 2) HSPF simulations for three HUC 8 watersheds; and 3) a customized version of USEPA’s HSPFParm database that will be populated with values from Minnesota HSPF model applications.

AQUA TERRA produced a guidance document that provides a standard methodology for HSPF model application steps, but also accounts for the need for flexibility in model construction in order to efficiently and comprehensively address the set of unique impairments within a watershed. The modeling guidance document addresses differences in watershed characteristics and impairments and offers approaches to address these differences.

AQUA TERRA also developed HSPF models for three 8-digit HUC watersheds: Crow Wing River (07010106), Redeye River (07010107), and Long Prairie River (07010108). When complete, these models will simulate hydrology at the 12-digit HUC subbasin scale (or finer). For each model, technical memoranda were developed that provide 1) a description of the model representation of point sources, 2) the rationale for the selection of flow records and locations for the purposes of the hydrologic calibration, and 3) discussion of the initial hydrology calibrations.

USEPA’s HSPF Parameter Database (HSPFParm) contains parameter values for HSPF model applications conducted across the United States. The set of parameters in HSPFParm characterizes a broad variety of physical settings, land use practices, and water quality constituents. A simplified interactive interface enables modelers to access and utilize HSPF parameter values for HSPFParm. AQUA TERRA customized and populated HSPFParm with parameters values from HSPF applications in Minnesota. The database expedites the future construction of HSPF models as well as increase the consistency among HSPF model applications in Minnesota.

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