PLRM

Pollutant load removal is estimated individually by BMP type. The user chooses a desired BMP icon in the schematic window and is then prompted to input design parameters such as water quality volume, size/footprint, infiltration rate, residence time, brim full draw down time, maximum flow, etc., depending on the BMP. Once inputs are finalized, the model is ready to run a simulation.

User is expected to directly enter specific values into the program, including the location of the project, catchment attributes, land use by type, soil information, road conditions, BMP implementation (as a percentage of land use), drainage conditions, and BMP parameters. To simulate catchments outside the Tahoe Basin, the user will require a more extensive amount of data to be able to represent the region, such as database files for rainfall, soil, land uses, etc.

PLRM will evaluate the source contributions and pollutant load reductions and then provide the user with three options of reports: recommended range, scenario summary, and detailed scenario summary. To find the estimation of pollutant load reduction, the supplemental report to the detailed scenario summary report should be accessed, specifically the “Stormwater Treatment” section of the supplement.

• Tool may be used during the planning phase of stormwater program
• Model was originally built for the Lake Tahoe Basin but can be modified to simulate other drainage areas provided that watershed characteristics are inputted into the Microsoft Access database by the user
• Model factors in groundwater, evapotranspiration, and snowmelt, but not in-stream transport, and it does not provide the user the option of loading in point sources
• Output may be inaccurate if modelling outside of the recommended scale i.e. small catchments become very sensitive to rainfall intensity, and the model uses simplified routines for hydrologic routing that may not represent runoff characteristics in large catchments
• Not recommended for modelling non-urban areas.
• Designed for areas with a low water table, so may not accurately model high groundwater conditions
• This tool is free and available to the public