1. Hydrologic Modeling with SSARR and HEC-HMS
Crane Johnson, PE
Hydraulic Engineer
US Army Corps of Engineers
Alaska District

2. Streamflow Synthesis and Reservoir Regulation Model
SSARR
Streamflow Synthesis and Reservoir Regulation Model
Streamflow Synthesis and Reservoir Regulation (SSARR) Model was developed to provide mathematical hydrologic simulations for systems analysis as required for the planning, design, and operation of water control works.
Consists of two Sub-models:
Watershed Model
River System and Regulation Model

3. SSARR
Developed in the 1960’s by the Corp of Engineers Northwest Division, last major update 1991
Still used today to model un-regulated Columbia and Snake River flows
Written in FORTRAN 77, DOS Operating System
Used by the Alaska District as an Operational model to forecast flood flows for the Chena River Lakes Project.

4. FAIRBANKS FLOOD OF 1967 6.20” of rain in Fairbanks (August 1967)
74,000 cfs, Downtown Fairbanks
Photo courtesy of VF Addendum, , Archives,
University of Alaska Fairbanks.
Displaced 7,000 People
$80 Million in Damages
Inspired Congress to pass the National Flood Insurance Program (NFIP)

5. Chena River Lakes Project
1958 – Project Authorized
1968 – Project Re-Authorized
1970 – Design Begins
1973 – Tanana Levee Construction Begins
1975 – Moose Creek Dam Construction Begins
1979 – Moose Creek Dam Operational
1981 – Project Test Fill
1988 – Construction of All Project Elements Complete

6. CHENA RIVER LAKES PROJECT OPERATIONAL SCHEMATIC

7. DAM SPECIFICATIONS TYPE: Zoned Earth Fill
ALASKA DISTRICT
TYPE: Zoned Earth Fill
ELEVATION: Feet MSL top)
HEIGHT ABOVE STREAM BED: 50 feet
LENGTH: 40,200 feet
WIDTH AT TOP: 24 feet
VOLUME OF FILL: 6,231,000 cubic yards
STORAGE CAPACITY: 224,000 acre-feet
@ 525 feet control works

8. DISCHARGE FACILITY Type: Concrete gravity control works
ALASKA DISTRICT
Type: Concrete gravity control works
Gates: 4 steel, vertical lift
Gate Openings: 18 ft high X 25 ft wide
Fishways: 2 each, 5 ft wide X 18 ft high
Fish Ladder: Vertical slot width = 0.75 feet
Maximum discharge = 26 cfs

9. CHENA FLOODWAY Length: 27,000 ft (Chena River to Highway Bridges)
Minimum Width of cleared flow channel: 1,100 feet
Maximum Width of cleared flow channel: 4,200 feet
Channel-peak design outflow: 160,000 cubic feet per second
Floodway Sill:
Type: Sharp-Crested Weir
Material: Sheet piling with
rolled concrete stilling basin
Crest Elevation: feet (MSL)
Crest Length: 2,000 feet
Purpose: Prevent Tanana River floods
from entering Chena River.

10. HIGH WATER EVENTS 20 High Water Events from 1981 through 2008
ALASKA DISTRICT
20 High Water Events from 1981 through 2008
The 3 Largest Events to Date:
Peak Peak Peak Gate
Floodway Closure
Elevation Outlet Works Fairbanks Duration
Dates Feet (MSL) (CFS) (CFS) (DAYS)
May-June ,200 10,
May ,300 11,
May-June , ,

11. CHENA RIVER LAKES FLOOD CONTROL PROJECT
ALASKA DISTRICT
Chena Water Shed. COE River sites shown (5) and remote meteorological sites(6). Several other realtime wx sites are shown. Currently these sites are not included in our model simulations, but should be included in the future. During this past event data from the site in the ‘Lower Chena Basin’ was extremely valuable.

12. CHENA RIVER LAKES FLOOD CONTROL PROJECT
ALASKA DISTRICT
Chena River Lakes Project SSARR Model
Lumped parameter model with 4 sub-basins
Each sub-basin includes elevation bands
Moose Creek Dam and Reservoir Included
Two sets of operating rules
Maximum release
Minimum release (upstream fish migration)
Chena Water Shed. COE River sites shown (5) and remote meteorological sites(6). Several other realtime wx sites are shown. Currently these sites are not included in our model simulations, but should be included in the future. During this past event data from the site in the ‘Lower Chena Basin’ was extremely valuable.

13. CHENA BASIN SSARR MODEL
ALASKA DISTRICT
CHENA BASIN SSARR MODEL
Watershed Sub-Model
Basin weighted averages (with elevation zone adjustments) for:
Air Temp
Precipitation
Interception – Bucket Model
Evapotranspiration – Thornwaite Method
(adjusted for elevation, season and snowcover)
Snowmelt – Temperature Index Method
Runoff – Empirical relationship SMI vs. Runoff%
(varies with rainfall rate)
Four runoff zones are routed to the Stream
(routing through series of small lakes)

14. CHENA BASIN SSARR MODEL
ALASKA DISTRICT
CHENA BASIN SSARR MODEL
River System and Regulation Sub-Model
Reservoir Routing – Continuity of storage equation
Stream Routing – Cascade of reservoirs
Time of Storage decreases with increasing Q
KTS
Ts= Qn

15. CHENA BASIN SSARR MODEL
ALASKA DISTRICT

16. CHENA BASIN SSARR MODEL
ALASKA DISTRICT
CHENA BASIN SSARR MODEL
Strengths:
Includes both watershed and river routing processes
Includes reservoirs and regulation operating rules
Long history of use in Interior Alaska
Empirically based methods with lots of calibration data
Weaknesses:
Difficult user interface
Limited graphical output capabilities
Empirically based model – limited hydrologic methods available
No automatic adjustment of initial conditions available

17. Hydrologic Engineering Center - Hydrologic Modeling System
HEC-HMS
Hydrologic Engineering Center -
Hydrologic Modeling System
(formerly HEC-1)
HEC “NexGen” Project Begins 1990
(RAS, HMS, FDA)
First HEC-HMS Release April 1998
Version 1.1 Released April 1999
Current Version 3.4

18. HEC-1 HEC-HMS Purpose of HEC-HMS Importance of HEC-HMS HEC-HMS
ALASKA DISTRICT
HEC-1
HEC-HMS
Purpose of HEC-HMS
Improved User Interface, Graphics, and Reporting
Improved Hydrologic Computations
Integration of Related Hydrologic Capabilities
Importance of HEC-HMS
Foundation for Future Hydrologic Software
Replacement for HEC-1 (Advanced Version)

19. IMPROVEMENTS OVER HEC-1
HEC-HMS
ALASKA DISTRICT
IMPROVEMENTS OVER HEC-1
Ease of use
Projects divided into three components
User can run projects with different parameters instead of creating new projects
Hydrologic data stored as DSS files
Capable of handling NEXRAD-rainfall data and gridded precipitation
Quasi-distributed model

20. Processes for each Basin
HEC-HMS
ALASKA DISTRICT
3 Major Hydrologic
Processes for each Basin
Losses (10 methods)
Transformation to runoff (7 methods)
Transformation to baseflow (5 methods)

21. Six Streamflow Routing Methods
HEC-HMS
ALASKA DISTRICT
Six Streamflow Routing Methods
Hydraulic Methods
Kinematic Wave Method
Muskingum-Cunge Method
Hydrologic Methods
Muskingum Method
Storage Method (Modified Puls)
Lag Method

22. EKLUTNA HEC-HMS MODEL
ALASKA DISTRICT

23. CHENA RIVER LAKES PROJECT
ALASKA DISTRICT
Advantages
SSARR HEC-HMS

24. QUESTIONS????
ALASKA DISTRICT