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HEC-5: Simulation of Flood Control and Conservation Systems VERSION/DATE: Version 8.0; October 1998 (recompiled May 04) OPERATING SYSTEM: DOS DISTRIBUTOR: HEC DOCUMENTATION (389 Pages): HEC-5 Users Manual, October 1998 US Army Corps of Engineers Hydrologic Engineering Center ABSTRACT 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. ORIGIN OF PROGRAM 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 Manual. 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 |
