1.   Purpose and objectives

     The program uses reservoir storage - discharge data to route inflow hydrographs through a potential reservoir and to proportion the structure according to Natural Resource Conservation Service (NRCS) criteria. Technology developed by the Agricultural Research Service (ARS) evaluates the stability and integrity of the auxiliary spillway. Inflow hydrographs may be actual or developed from any storm rainfall distribution.

2.   Description

     Storage and discharge capacities may be computed by the program or input by the user. The discharge capacity consists of principal and auxiliary spillway flows. The structure routing is done using the storage indication method of reservoir routing. Auxiliary spillways discharges can be computed by water surface profile methods using a combination of the direct step and standard step techniques. NRCS design hydrologic and hydraulic criteria and procedures are used throughout the program.

3.   Input

     The program uses a control word concept with line input, and a Windows interface is under development. Inflow hydrographs are generated from storm rainfall using a dimensionless unit hydrograph, drainage area, time of concentration, and an NRCS curve number. Spillway rating curves can be computed by entering physical and hydraulic parameters. Elevation-surface area data can be used to compute reservoir capacity for the structure routing.

4.   Output

     Output options permit the user to control the volume of output data compatible with the number of design alternatives being considered. Output can include detailed lists of design parameters, rating tables, digital plots of inflow and outflow hydrographs, and other parameters of interest.

5.   Operational requirements and restrictions

     a. One person with basic knowledge of watershed hydrology and 
        hydraulics and a basic familiarity with computers and computer 
        software can use the program.
  
     b. At least one day of training is helpful to use the program plus 
        several additional days if the user is unfamiliar with NRCS
        hydrologic techniques or the ARS erosion technology.
  
     c. The program was written for personal computer systems in FORTRAN. 
        Memory requirements are 0.5 to 1.0 megabytes of storage space. 
  
     d. In each pass up to five auxiliary spillway bottom widths and up to 
        five auxiliary spillway crest elevations may be considered for a 
        structure site without updating the input data.
  
     e. The program accepts data for single structures and for sites in 
        series.
    
     f. The typical range of structure design application has been on 
        watersheds ranging from 0.5 to 50 sq. miles (1 to 130 sq. km).

6.   Form of presentation
        
     Program is on CD, with User Manual. Both program and manual are posted on the Internet, at http://www.wcc.nrcs.usda.gov

7.   Operational experience

     The program is used extensively by the U.S. Natural Resources Conservation Service and by State and local agencies with good results.

8.   Originator and technical support

     Water Science Technology Team, National Water and Climate Center, Natural Resources Conservation Service, U.S. Department of Agriculture.

9.   Availability

     From the HOMS National Centre for USA.

10.  Conditions on use

     None.