The following is one of over 75 programs & documentation included with Hydro-CD by Dodson

HEC-5: Simulation of Flood Control and Conservation Systems

VERSION/DATE: Version 8.0; October 1998 (recompiled May 04)




HEC-5 Users Manual, October 1998
US Army Corps of Engineers 
Hydrologic Engineering Center


This program was developed to assist in planning studies for evaluating proposed reservoirs in a system and to assist in sizing the flood control and conservation storage requirements for each project recommended for the system. The program can be used in studies made immediately after the occurrence of a flood to evaluate preproject conditions and to show the effects of existing and/or proposed reservoirs on flown and damages in the system. The program should also be useful in selecting the proper reservoir releases throughout the system during flood emergencies in order to minimize flooding as much as possible and yet empty the system as quickly as possible while maintaining a balance of flood control storage among the reservoirs.

The above purposes are accomplished by simulating the sequential operation of a system of reservoirs of any configuration for short Interval historical or synthetic floods or for long duration nonflood periods or for combinations of the two. Specifically the program may be used to determine:

a. Flood control and conservation storage requirements for each reservoir in the system.

b. The influence of a system of reservoirs on the spatial and temporal distribution of runoff in a basin.

c. The evaluation of operational criteria for both flood control and conservation (including hydropower) for a system of reservoirs.

d. The expected annual flood damages, systems costs, and system net benefits for flood damage reduction.

e. The system of existing and proposed reservoirs or other alternatives including nonstructural alternatives that results in the maximum net flood control benefits for the system by making simulation runs for selected alternative systems.


This program was developed at The Hydrologic Engineering Center by Bill S. Eichert. The initial version was written for flood control operation of a single flood event and was released as HEC-5, "Reservoir System Operation for Flood Control," in May 1973. The program was then expanded to include operation for conservation purposes and for period-of-record routings. This revised program was referred to an REC-SC up to the February 1978 version. The June 1979 version was the last major release of the program. The April 1982 version of HEC-5 supersedes all previous versions and is the version this manual documents.

Release Notes

Since the last release of computer program HEC-5 (Version 7.2, March 1991),
several new features have been developed. In addition, several program
dimension limits have been increased to allow a greater number of reservoirs,
hydropower plants, control points, and diversions. The HEC-5 User's Manual,
October 1998, documents this program version.

Important Note: HEC-5, Version 8.0 has been implemented using Extended
Memory on the PC (runs in a MS DOS Prompt Window or in MS-DOS mode). An
"overlaid" low-memory (640 Kb) edition was available for the March 1991
release; however, Version 8 will not be available in that form.

New Program Features and Modifications

1. Three new CASE output variables have been added to provide improved
understanding of hydropower simulations. These added variables
distinguish between releases based on the following operations: Leakage
(CASE =0.13); power production limited by Penstock (CASE=0.14); and,
power production limited by Generator Capacity (CASE=0.15). For a
listing of the CASE definitions, refer to Table 2.2, on page 2-13 in the
HEC-5 User's Manual or to an HEC-5 output file (*CASES).

2. A new operational priority has been added to curtail tandem reservoir
operation at the top of buffer level, instead of allowing tandem
operation down to the inactive storage level. For this option refer to
the input description for the J2 Record, field 4 (IPRIO=128), on page
G-7 in the HEC-5 User's Manual.

3. Flow-Through Reservoir Option: A new type of reservoir specification
has been added to the program for use in systems where a storage
reservoir operates directly for water supply locations that are below a
downstream "tandem" reservoir. The downstream tandem reservoir may be
specified as a "flow-through" reservoir (which operates as a run-of-
river reservoir). This option allows the upstream reservoir to more
precisely account for the effect of evaporation, diversions and local
flows at the designated flow-through reservoir when making water supply
releases to meet a water supply goal below the flow-through reservoir.
To specify this type of operation, the flow-through reservoir is
indicated with a negative location number on the RL record. For this
option refer to the input description for the RL Record, field 1, on
page G-32 in the HEC-5 User's Manual.
4. Multiple Reservoir Outlet Capacities: The specification of multiple
outlet capacities (RQ records), which allow the backwater effects of
downstream reservoirs or non-reservoirs to limit reservoir releases, is
now possible. For this option refer to the input description for the
added QQ Record, on page G-35, and for the RQ Record, field 1, on page
G-36 in the HEC-5 User's Manual.

5. The input description for the RG record (for gated spillway surcharge
operation) has been revised to allow the specification of the elevation
at which the reservoir will resume normal operation with decimal values
rather than integer values. For more information on this modification,
refer to the input description for the RG Record, fields 9 and 10, on
page G-44 in the HEC-5 User's Manual. As an added note, if the previous
style of the RG Record is input, the program will halt operation and
print a message.

6. Pumped-storage power simulation has been improved to allow the primary
reservoir to operate for locations below its re-regulation reservoir
(instead of relying on the re-regulation reservoir to operate for
downstream locations). For information on pumped storage simulation,
refer to Section E.4 "Pumped-Storage", on page E-25, and to the input
description for the P1 Record, field 2, on page G-45 in the HEC-5 User's

7. The power leakage has been modified to continue until the top of
inactive pool is reached (instead of turning off when the reservoir
level reaches top of buffer pool). For more information on leakage,
refer to the input description for the P2 Record, field 1, on page G-47
in the HEC-5 User's Manual.

8. The simulation of "tandem power" reservoirs utilizing PD records with a
daily simulation interval has been improved by providing the ability to
optionally turn off tandem releases on non-power operation days. For
this option, refer to the input description for the PD Record, on page
G-50, and for the RO Record, on page G-34 in the HEC-5 User's Manual.

9. An additional diversion option has been added which provides the
capability for a diversion to be based on the flow at a reference
location. For this option, refer to the input description for the DR
Record, fields 9 and 10, on page G-64 in the HEC-5 User's Manual.

10. A new capability to define a minimum desired flow as a function of
natural flows has been added. This capability allows the specification
of a minimum desired flow at a non-reservoir location which is based on
a ratio of natural flow accruing in the basin above the location. The
basis for determining the minimum flow is also based on the annual
volume of natural runoff and the status of storage in a designated
reservoir. For this option, refer to the input description for the WA
Record, on pages G-78 and G-79 in the HEC-5 User's Manual.
11. The treatment of missing data (indicated by a value of -901) read from a
DSS file has been updated to handle missing data in the following
manner: missing data in a time series prior to a valid data entry will
be assumed to be 0.0; missing data between two valid entries will be
set equal to the last valid data entry prior to the missing data; and,
missing data following the last valid data entry will be set to 0.0.
Whenever missing data is read from a DSS file, a "warning" message is
displayed in the HEC-5 output file. For information on reading time
series data from HEC-DSS files, refer to pages G-86 and G-87 in the HEC-
5 User's Manual.

12. The ability to specify a four-digit year for the beginning of the
simulation period has been added to the BF record. If the century (e.g.
1800 or 2000) is not indicated in the input, the program will assume the
century for the year is 1900. For this option, refer to the input
description for the BF Record, field 10, on page G-89 in the HEC-5
User's Manual.
13. The specification of evaporation time series data as input with EV
records has been changed from a monthly rate (mm or inches per month) to
a period rate (mm or inches per period). The length of the period is the
simulation interval as defined by the BF Record, field 7. For
information on time series evaporation input, refer to page G-100 in the
HEC-5 User's Manual.

Program Dimension Limits

HEC-5 dimension limits have been increased to accommodate the
requirements of several large period-of-record studies. The dimension limits
for Version 7.2, March 1991 (Extended Memory) and Version 8.0, October 1998
are shown in the following table. Program dimension limits are also shown at
the beginning of the output file created during program execution.

Dimension Limit Version 7.2 Version 8.0
for: March 91 October 98
Reservoirs 20 40
Hydropower Plants 12 35
Control Points 40 80
Diversions 20 40
Input Records 800 1000
User Defined Output Tables 20 80
2012 - Walter P. Moore & Associates, Inc. - Houston, TX, USA