Hydrologic Modeling with SSARR and HEC-HMS
Crane Johnson, PEHydraulic EngineerUS Army Corps of EngineersAlaska District
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
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.
SSARR
FAIRBANKS FLOOD OF 1967
Photo courtesy of VF Addendum, 89-12-83, Archives,
University of Alaska Fairbanks.
•Displaced 7,000 People
•$80 Million in Damages
•Inspired Congress to pass the National Flood Insurance Program (NFIP)
•6.20” of rain in Fairbanks (August 1967)
•74,000 cfs, Downtown Fairbanks
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
CHENA RIVER LAKES PROJECT
OPERATIONAL SCHEMATIC
ALASKA DISTRICT
DAM SPECIFICATIONS
• TYPE: Zoned Earth Fill• ELEVATION: 528.7 Feet MSL (max @ 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 elevation @ control works
ALASKA DISTRICT
DISCHARGE FACILITY
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
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: 506.65 feet (MSL)
• Crest Length: 2,000 feet
• Purpose: Prevent Tanana River floods
from entering Chena River.
ALASKA DISTRICT
HIGH WATER EVENTS
• 20 High Water Events from 1981 through 2008
• The 3 Largest Events to Date:
Peak Peak Peak Gate
Floodway Flow @ Flow @ Closure
Elevation Outlet Works Fairbanks Duration
Dates Feet (MSL) (CFS) (CFS) (DAYS)
May-June 1992 507.6 8,200 10,500 18
May 1991 503.0 8,300 11,350 11
May-June 1985 505.3 8,250 8,950 12
ALASKA DISTRICT
CHENA RIVER LAKES FLOOD CONTROL PROJECT
ALASKA DISTRICT
CHENA RIVER LAKES FLOOD CONTROL PROJECT
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)
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)
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
Ts= KTS
Qn
ALASKA DISTRICT
CHENA BASIN SSARR MODEL
ALASKA DISTRICT
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
CHENA BASIN SSARR MODEL
Hydrologic Engineering Center -
Hydrologic Modeling System
(formerly HEC-1)
HEC-HMS
•HEC “NexGen” Project Begins 1990 (RAS, HMS, FDA)
First HEC-HMS Release April 1998•Version 1.1 Released April 1999•Current Version 3.4
ALASKA DISTRICT
HEC-HMS
HEC-HMS HEC-1 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)
ALASKA DISTRICT
HEC-HMS
– 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
IMPROVEMENTS OVER HEC-1
ALASKA DISTRICT
HEC-HMS
3 Major Hydrologic
Processes for each Basin
•Losses (10 methods)
•Transformation to runoff (7 methods)
•Transformation to baseflow (5 methods)
ALASKA DISTRICT
HEC-HMS
Hydraulic Methods Kinematic Wave MethodMuskingum-Cunge Method
Hydrologic MethodsMuskingum MethodStorage Method (Modified Puls)Lag Method
Six Streamflow Routing Methods
ALASKA DISTRICT
EKLUTNA HEC-HMS MODEL
ALASKA DISTRICT
CHENA RIVER LAKES PROJECT
SSARR HEC-HMSAdvantages
ALASKA DISTRICT
QUESTIONS????