HSPEXP+ was developed by RESPEC to be the next generation of HSPEXP, which was originally developed by the US Geological Survey (USGS).  HSPEXP+ has been completely redesigned and shares only some of the legacy input file format, mathematical formulae, and algorithms from HSPEXP.  HSPEXP+ is an enhanced expert system that can perform additional functions and has evolved into a comprehensive tool for hydrologic and water quality calibration, quality assurance/quality control (QA/QC), sensitivity analysis, uncertainty analysis, and scenario comparisons for HSPF models.

HSPEXP+ generates time series plots comparing observed and simulated data, hydrology calibration statistics, hydrology calibration advice, constituent balance reports, reach budget reports, box-whisker plots of constituent loading by land use, monthly constituent loadings by land use, and Regan plots to evaluate model stability. HSPEXP+ is an open-source project and is available for no cost at RESPEC’s
GitHub site.  A detailed description of the individual capabilities of HSPEXP+ is provided at https://www.chijournal.org/C422.


Clients use HSPEXP+ to:

  • Generate graphs, error statistics, and reports to assist in HSPF hydrology and water quality calibration and validation.
  • Conduct QA/QC of existing HSPF models.
  • Conduct HSPF model scenario analysis.
  • Conduct sensitivity and uncertainty analyses of an HSPF model.