Skip to main content
ARS Home » Research » Software » Download

headline bar
Small Watershed Hydrology (WinTR-55)

Welcome to the software download area! Please contact us if you have problems or questions.

Download Available

Current Version

WinTr-55, Version 1.10

Historical Background

Technical Release 55 (TR-55) Urban Hydrology for Small Watersheds was first issued in January 1975 as a simplified procedure to calculate the storm runoff volume, peak rate of discharge, hydrographs and storage volumes required for storm water management structures (SCS, 1975). The first issue involved manual methods and assumed the NRCS Type II rainfall distribution for all calculations.

In June 1986 major revisions were made in TR-55 by adding three rainfall distributions (Type I, IA and III) and programming the computations.  Time of concentration was estimated by splitting the hydraulic flow path into separate flow phases (SCS, 1986).  The computer program became a standard tool to analyze peak flow changes caused by urbanization in many locations.  Its wide acceptance by public and private users has also indicated where improvements could be made in the procedures and the computer program.

A WinTR-55 work group was formed in the spring of 1998 to modernize and revise the Technical Release and the computer software.  The current changes include: upgrade the source code to Visual Basic, change the philosophy of data input, develop a Windows interface and output post- processor, enhance the hydrograph-generation capability of the software and flood route hydrographs through stream reaches and reservoirs.

  • The availability and technical capabilities of the personal computer have significantly changed the philosophy of problem-solving for the engineer. Computer availability eliminated the need for WinTR-55 Guide methods, thus the guide portions (graphs and tables) of the user document have been eliminated. This user guide covers the procedures used in and the operation of the WinTR-55 computer program.  Part 630 of the Natural Resources Conservation Service (NRCS) National Engineering Handbook provides detailed information on NRCS hydrology and is the technical reference for this document.  Appendix C of the WinTR-55 User Guide (part of the install package) contains a list of the Part 630 chapters and their subjects.  Users who are not familiar with NRCS hydrologic procedures should refer to the appropriate chapters for background information and the details of procedural techniques.

Download Form

Please complete the form below to track the use of the service we are providing and to help improve our product.
OMB 0518 - 0032 (01/2025)
First Name   
Last Name   

According to the Paperwork Reduction Act of 1995, an agency cannot conduct or sponsor, and a person is not required to respond to, a collection of information unless it displays a valid OMB control number. The valid OMB control number for this information collection is 0518-0032. The time required to complete this information is estimated to vary from one to five minutes with an average of three minutes per response, including time for reviewing instructions, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Agriculture, Clearance Officer, OIRM, Room 404-W, Washington, DC 20250, and to the Office of Information and Regulatory Affairs, Office of Management and Budget.