AQUA TERRA Consultants

An Enhanced Expert System for Calibration of HSPF (HSPEXP+)

HSPEXP+ is being developed by RESPEC to support calibration of watershed models developed using HSPF. It is an open source project and released free of cost to support other modelers who are using HSPF. It is under active development, and no active support is available for HSPEXP+ by RESPEC or any other agency. RESPEC and the authors do not assume any responsibility for system operation, output, interpretation, or use.

Please refer to the HSPEXP+ user's manual, available with the installation, to learn about its functionalities and limitations.


The Clean Water Fund of Minnesota partially supported the development of HSPEXP+, and is continuing to support the new enhancements. RESPEC also acknowledges following modelers who tested the initial versions of HSPEXP+ and provided valuable feedback.

User Assistance and Feedback

As indicated earlier, active support for HSPEXP+ is not available; however feedback may be provided at Please register as HSPEXP+ user to be informed of future updates.

Reference to HSPEXP+

Reference to HSPEXP+ should be as follows.

Mishra, A., P.B. Duda, M. H. Gray, B. R. Bicknell, A.S. Donigian, and R. W. Zeckoski. 2015. HSPEXP+ Version 1.20 User's Manual. Developed by RESPEC, Mountain View, CA. Available at

RESPEC released HSPEXP+1.20 (A bug fixed version HSPEXP+1.21 is now available!) on 11/15/2016. Please review the changes in HSPEXP+ 1.21 during the installation and update your current installation of HSPEXP+ by uninstalling it and then installing the latest version.

HSPEXP+ code is now available on Github along with the BASINS Code. You can follow the BASINS and HSPEXP+ development on Github by visiting Github BASINS site.

Download HSPEXP+ 1.21 by clicking on the link below.

You may also download example files for an uncalibrated HSPF model for hydrology (125MB).

Future direction of HSPEXP+

We are looking forward to developing additional capabilities in HSPEXP+, as resources are available. Some possible future enhancements include the following:

  • Generating reports for additional water quality constituents
  • Flexibility for using it with English or Metric units
  • Capability to generate the basin-specification (EXS) file interactively
  • Capability to calculate calibration statistics with non-continuous observed data
  • Capability to conduct sensitivity and uncertainty analysis.