AQUA TERRA Consultants
AQUA TERRA Services

SARA Load Reduction Tool


The SARA Load Reduction Tool was developed to allow users to determine the constituent load reductions needed to reach water quality standards in model reaches within a watershed through the application of BMPs.

The tool requires a working HSPF UCI file, corresponding input and output WDM files, and a BMP application specification file (referred to as "spec file" from here onwards). The spec file allows the user to define:

  • The list of landuses for BMP application, for each subbasin, and the percentage of available area for BMP implementation.
  • Screening levels for each constituent/reach combination, providing the targets the tool seeks to meet by comparing them to the modeled flow-weighted average concentrations.
  • A tolerance value is provided per constituent/reach combination allowing control of the "closeness" of the resulting concentration to its target.
  • Maximum BMP reduction factor for each constituent.
  • A flag for conducting log-transformation on concentration values for specified constituent/reach combinations.
  • A list of point sources to be considered as potential constituent reduction sources should regular land based BMP reductions does not meet the target screening levels.

The tool uses the specification file to apply BMPs in an upstream-to-downstream direction in the model watershed to reduce constituent loads to a reach. The end of run comes under 3 situations:

  • Maximum number of runs reached
  • No more BMP load reduction can be applied
  • All constituents in all reaches met their target screening levels

Users can carry out the whole process in either manual or auto-run mode. Report and template specification files can be generated using the tool as well.

AQUA TERRA Consultants created this tool for the San Antonio River Authority (SARA) and would like to acknowledge SARA and its contractor, Atkins, for their financial and technical support under the direction and management of Dr. Sheeba M. Thomas, Dr. Aarin Teague and Dr. Russell Persyn of SARA. SARA, Atkins and AQUA TERRA Consultants cannot assume responsibility for operation, output, interpretation or use of this software.

SARA Atkins