Real-time Flood Forecasting in Iowa with a Data Assimilated Hydrological
Model
Scott J. SmallThe Iowa Flood Center
IIHR Hydroscience & EngineeringThe University of Iowa
Real-time flood forecasting in Iowa
Streamflow forecasts are produced: Every hour For 10 days At over 2000
locations
Streamflow forecasts based on the IFC model are publicly available in the Iowa Flood Information System (http://iowafloodcenter.org/)
Flood warnings at points of interest
Streamflow forecasts based on the IFC model are publicly available in the Iowa Flood Information System (http://iowafloodcenter.org/)
Iowa Flood CentersDistributed Hydrological Model
Example of Landscape decomposition (Turkey River)
Parameters describing soil conductivity, infiltration
capacity, slope, and roughness are assigned to
each terrain unit
Example of Landscape decomposition (Turkey River)
Statewide implementationOur distributed hydrological model provides streamflow predictions everywhere in Iowa
About 420,000 individual hillslopes
IFC Modelling Framework
Four ODEs per hillslope
Mass Conservation Equations
Fluxes between control volumes
Channel Routing
Radar rainfall coverage of Iowa
0.004167 degree spatial resolution (about 300m by 400m)
5 minute temporal resolution
Custom numerical solvers produce solutions to the system of differential equations
ASYNCH numerical solver for ODEs with a tree structure
Developed at the Iowa Flood Center for distributed hydrological models
Runs on distributed memory architectures
Written in C
Combining streamflow observations withmodel projections
Observations
USGS Streamflow Gauges Around 200 in Iowa 15 minute resolution
IFC Bridge Sensors Around 200 in Iowa 15 minute resolution Rating curves under
development
USGS Gauges and IFC Bridge Sensors
Given a collection of observations over a period of time, what initial model states best reproduce the observations?
Data assimilation performed through a least squares fitting of model inputs
Find the discharge at each channel minimizing the energy functional
with the linearized model discharges
and discharge sensitivity matrix H and observation vector d.
Calculating the sensitivity matrix requires solving an additional ODE at each link for every upstream link
Links too far from a gauge can be ignored in the sensitivity matrix
Travel times with (high) linear velocity can limit greatly calculations.
Iowa Flood CentersStreamflow Forecasting System
IFIS
Real-time flood forecasting with data assimilation
BackgroundTime
Time ofForecast
1. Model channel discharges are selected at the background time to fit data
Real-time flood forecasting with data assimilation
AssimilationPeriod
BackgroundTime
Time ofForecast
1. Model channel discharges are selected at the background time to fit data
2. Model is advanced to the time of forecast
Real-time flood forecasting with data assimilation
AssimilationPeriod Forecast
BackgroundTime
Time ofForecast
1. Model channel discharges are selected at the background time to fit data
2. Model is advanced to the time of forecast
3. Model based forecast is produced
Iowa River above the city Marengo, IA
7,200 km2drainage area(18,000 hillslopes)
10 available USGSGauges
Forecasts from June 20th, 2015
Future Work and Additions
Expand data assimilation domain to the entire state of Iowa
Incorporate Iowa Flood Center bridge sensor data (requires rating curves)
Adjust hillslope model states based upon streamflow observations
Incorporate observation and model uncertainty
Real-time Flood Forecasting in Iowa with a Data Assimilated Hydrological ModelReal-time flood forecasting in IowaFlood warnings at points of interestIowa Flood CentersDistributed Hydrological ModelSlide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Custom numerical solvers produce solutions to the system of differential equationsCombining streamflow observations with model projectionsObservationsUSGS Gauges and IFC Bridge SensorsSlide Number 17Data assimilation performed through a least squares fitting of model inputsLinks too far from a gauge can be ignored in the sensitivity matrixIowa Flood Centers Streamflow Forecasting SystemReal-time flood forecasting with data assimilationReal-time flood forecasting with data assimilationReal-time flood forecasting with data assimilationIowa River above the city Marengo, IASlide Number 25Future Work and Additions
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