|WORLD METEOROLOGICAL ORGANIZATION||
|Explanation of the criteria for classification and numbering of components|| K22.3.02
|Explanation of the dates on the component's description|
COMPUTER PROGRAM FOR PROJECT FORMULATION - HYDROLOGY (TR-20)
1. Purpose and objectives
The program provides for hydrologic analyses of a watershed under present conditions and with various combinations of land cover, use and
structural or channel modifications using single event storm rainfall-
TR-20 generates subarea surface runoff hydrographs from storm rainfall using a dimensionless unit hydrograph, drainage areas, times of
concentration, and NRCS runoff curve numbers. Standard control instructions
to develop, route, add, store, divert or divide hydrographs are established
to convey floodwater from the headwaters to the watershed outlet. Uniform
rain depth and distribution are assumed over a subarea, groups of
sequential subareas or the whole watershed.
The program uses batch input. The required data are: sequential
standard control instructions which include drainage area, time of concentration and the NRCS runoff curve number for each subarea: structure
tables - elevation, discharge, and storage data; cross section tables -
elevations, discharge, and end area data or optional routing coefficients; reach lengths; main time increment; dimensionless unit hydrographs; baseflow; storm rainfall tables - depth, duration, distribution, and starting time data; and the soil moisture conditions - wet, average, dry.
The program provides in tabular form peaks and flood hydrographs, their time of occurrence and water surface elevations at any desired location in the watershed.
5. Operational requirements and restrictions
a. One person can use the program with basic knowledge of watershed
b. The program was written for personal computer systems in
c. In one continuous operation, the program con route through 99
d. Both the reach routing and reservoir routing techniques use the
6. Form of presentation
The program is on a diskette and a hard copy of the user manual is available.
The technique is used extensively by the U.S. Natural Resources
Conservation Service with good results, and is used worldwide.
8. Originator and technical support
Water Science Technology Team
10. Conditions on use
Reclassified from J20.3.02 MAR 1987
(First entered:03 FEB 81
Last updated: APR 98)