P8 Urban Catchment Model

Program for Predicting Polluting Particle Passage
 thru Pits, Puddles, & Ponds

William W. Walker, Jr., Ph.D.
Environmental Engineer
Concord, Massachusetts

Jeffrey D. Walker, Ph.D.
Environmental and Water Resource Engineer
Brunswick, Maine

January 17, 2017

Current Documentation - Online Help File

Menu Screen    Procedures    Devices    Mass Balances   Tables    Graphics    Demo Case

Model Reviews & Reports P8 Applications

Windows Version 3.5

prepared without agency support

March 2015

Download  Here

Windows Version 3.4

prepared for

USEPA, Minnesota PCA & Wisconsin DNR

October 2007

Download  Here

DOS Versions 1.1 thru 2.4

prepared for

Narragansett Bay Project / USEPA, Rhode Island DEM,
IEP Inc., Wisconsin DNR, et al

1990 - 2000

1.1 - May 1990 | 2.0 - June 1997 | 2.1 - June 1998 | 2.2 - Oct 19982.3 - Jan 1999 | 2.4 - Feb 2000

  | Download Complete DOS Package  |  

A B S T R A C T - Version 1.1 - 1990

P8 is a model for predicting the generation and transport of stormwater runoff pollutants in urban watersheds. Continuous water-balance and mass-balance calculations are performed on a user-defined system consisting of the following elements:

- Watersheds (nonpoint source areas, up to 24 (192 in Version 2.4+)

- Devices (runoff storage/treatment areas or BMP's, up to 24 (48 in Version 2.4+)

- Particle Classes (up to 5)

- Water Quality Components (up to 10)

Simulations are driven by continuous hourly rainfall and daily air temperature time series. The model has been developed for use by engineers and planners in designing and evaluating runoff treatment schemes for existing or proposed urban developments. The model is initially calibrated to predict runoff quality typical of that measured under the EPA's Nationwide Urban Runoff Program (Athayede et al., 1983) for Rhode Island rainfall patterns. Predicted water quality components include suspended solids (five size fractions), total phosphorus, total Kjeldahl nitrogen, copper, lead, zinc, and total hydrocarbons.

Primary applications include site BMP design to achieve total suspended solids removal efficiencies (70% or 85%) recommended by the Rhode Island Department of Environmental Management (1988). Simulated BMP types include detention ponds (wet, dry, extended), infiltration basins, swales, and buffer strips. Hydrologic components of the program are calibrated and tested against six years of daily streamflow data from the 15,000-acre Hunt-Potowomut watershed, Rhode Island. The model is used to examine the water quality implications of alternative treatment objectives.

Inputs are structured in terms which should be familiar to planners and engineers involved in hydrologic evaluation. Several tabular and graphic output formats are provided. The computer program runs on IBM-PC compatible microcomputers. This report documents the structure, calibration, testing, potential uses, and limitations of the program. A companion report (P8 Urban Catchment Model - User's Manual, IEP Inc., 1990) provides an overview and several example applications.

p8devic2.gif (27619 bytes)

Version 1.1 - May 1990

P8 Version 1.1 was prepared for the USEPA/ RIDEM Narragansett Bay Project & IEP Inc. in May 1990.  This version is no longer distributed.  See Version 2.4 below.

Partial documentation for Version 1.1 (minus figures & tables) is available here in PDF format. Viewing this file requires Adobe Acrobat Reader Version 4.0 . To download partial documentation, click here: P8 Partial Documentation (Text Only), P8DOC.PDF (0.2 mb).

Complete documentation for Version 1.1 (including basic equations, assumptions, calibration, figures, tables, etc.) is contained in file P8V1DOC.PDF (4.3 mb, Adobe Acrobat Reader Format).   A printed copy may be available from Rhode Island Department of Environmental Management (Richard Ribb, 401-277-4914).  

Version 2.0 - June 1997

P8 Version 2.0 was prepared for Wisconsin Department of Natural Resources & Minnesota Pollution Control Agency in June 1997.  Enhancements include:

        Snowfall/snowmelt simulation

        Enhanced street-sweeping routine

        Revised precipitation file format

        Additional ASCII output formats

        Calibrated particle files for Wisconsin watersheds

To view documentation using Adobe Acrobat Reader, click here: View P8 Version 2 Doc.

Version 2.0 Precipitation File Conversion Utility - June 1997

P8CONV.ZIP (165 Kb, 6/18/97) contains a conversion utility for creating precipitation data files to be used with P8 Versions 2.0 and higher.  It supports NOAA, Earth Info, and P8 Version 1.1 file formats.

To view documentation, click here: P8CONV Documentation.

Calibration to Wisconsin Watersheds, prepared for Wisconsin DNR, 1997.

Version 2.1 - June 1998

P8 Version 2.1 was prepared with partial support from CH2MHill, Inc. in June 1998.  Revisions include:

        Increase in the maximum number of watersheds from 24 to 192.

        Increase in the maximum number of devices from 24 to 48.

        Provision of ASCII file input/output interface for watershed data (potentially useful for generating model input data sets from Geographic Information Systems).

        Repairs of a minor bugs (plotting of elevations, simulations with multiple storm passes, reporting of snowmelt).

Version 2.2 - October 1998

Maintenance Release. Fixed errors in 'List Peaks', aquifer recharge from un-swept areas, and watershed index input screen. Activated case archiving & retrieval function.  No new features added.

Version 2.3 - January 1999

Format of flow calibration file (*.flo) modified for Y2K (now uses 4-digit years).  See sample file 'hunt.flo'. 

Modified for use with FAT32 file system (option under Windows 98).   If P8 is stored on a disk drive that uses FAT32, input file names must be entered directly.  The option to select input files from a list is available only with FAT file system.

The batch processing option is disabled in Version 2.3, but will be reinstated in a future version.

Version 2.4 - February 2000

Corrected output format problems with Version 2.3 when simulating cases with large numbers of devices and/or watersheds.

Corrected reporting of total rainfall over simulation period on menu screen. 

Revived sensitivity analysis.

File p8v24.zip (390 Kb) contains model, data files, & documentation of program changes. 

To install, expand into a convenient directory (e.g., C:\P8). See README file for further instructions.

Complete Package - DOS Version 2.4 and Supporting Documentation

To obtain a complete package with the most recent version of the model & documentation, you need to the download the following files:

        P8V1DOC.PDF   (4.2 Mb)  Original documentation with equations, assumptions, calibration, etc.

        P8_Users_Manual.PDF (6.1 MB) Original User's Manual, Version 1.1, instructions, sample applications 

         P8V2.PDF  (20 Kb)  P8 Version 2.0 documentation update

          P8CONV.ZIP  (165 Kb)  Precipitation file conversion utility & documentation

          P8V24.ZIP (390 Kb) Version 2.4 model & sample data files. With instructions for using ASCII input/output interface (file P8V21.DOC).

         Mn_Wi_P8_Climate.ZIP (300 Kb) Updated climate files for Wisconsin & Minnesota, July 2005

Model Reviews & Applications

Following is a compilation of articles on P8, including comparisons with other urban runoff models:

                  Palmstrom, N. & W. Walker, "The P8 Urban Catchment Model for Evaluating Nonpoint Source Controls at the Local Level", Enhancing States' Lake Management Programs, USEPA, 1990.

                  USEPA, "Compendium of Watershed-Scale Models for TMDL Development", Office of Water, EPA841-R-92-002, January 1992.

                  HDR Inc., "Evaluation of  Storm Water Computer Models", prepared for City of Minneapolis, 1992.

                  USEPA, "Compendium of Tools for Watershed Assessment & TMDL Development", Office of Water, EPA841-B-97-006, May 1997.

Technical Support for P8 is available for a fee.