National Weather Service River Forecast System NWSRFS Overview

1. National Weather ServiceRiver Forecast SystemNWSRFS Overview COMETHydromet 00-27 March 2000 2290 East Prospect Road, Suite 1 Fort Collins, Colorado 80525

2. Hydrologic Forecasting • Operational Forecasting and NWSRFS Overview • Sacramento Model • Model Calibration • ICP Workshop • Operational Forecasting • IFP Workshop • Extended Streamflow Prediction • ESP Workshop • FLOODWatch™

3. Hydrologic Forecasting “The integration of conceptual models, river and watershed characteristics, and real-time data to provide forecasts of future river conditions for both emergency response and long term water use planning.”

4. Elements of the Hydrologic Forecasting Process • Raw Data Collection and Storage • Pre-processing of Raw Data • Hydrologic Simulation • Forecast Adjustments • Extended Probabilistic Forecasts

5. Raw Data Collection and Storage • ALERT Type Networks • Precipitation, Stage • Event Based Transmission • Continuous Monitoring • Polled Stations • Radar Data

6. Pre-processing of Raw Data • Accumulation to Uniform Time Scale • Computation of Mean Areal Values 0.5 1.1 1.2 0.3 0.6 MAP = 0.76 0.8 0.7 0.2

7. Hydrologic Simulation • Snow Accumulation and Ablation • Rainfall-Runoff • Unit Hydrograph(Time Distribution of Runoff) • Channel Routing

8. Forecast Adjustments/Updating • Adjustment of Outputs to Observed Data • Updating Model States • Modifying Inputs and/or Parameters

9. Run-time Modifications

10. UZFW UZTW LZTW LZFP Extended Probabilistic Forecasting • Requires Continuous Models • Based on Current Model States

11. North Branch Main Stem SNOW-17 SAC-SMA S. Trib RES-SNGL LAG/K DWOPER SAC-SMA Forecast System Requirements • Hydrologic Inventory/Analysis • Model Selection/Configuration • Model Calibration

12. Processed Time Series Database Station Database Forecast Parameter Database North Branch Station 1 Location weights ident info Time Scale Characteristics Station 1 Location weights ident info Time Scale Characteristics Station 1 Location weights ident info Time Scale Characteristics Station 1 Location weights ident info Time Scale Characteristics Main Stem Station Database Station 1 Location weights ident info Time Scale Characteristics New Gages Terminated Gage S. Trib Forecast System Requirements (cont.) • System Setup andImplementation • Daily Operations • System Maintenance

13. Applications of Hydrologic Forecast Systems • Flash Flood Warnings • River Forecasts • Water Supply Forecasts • Reservoir Inflow Forecasts • Inundation Mapping • Water Management Activities

14. NWSRFS National Weather Service River Forecast System NWSRFS Overview

15. Hydrologic Forecast System • Data Collection • Precipitation and streamflow monitoring • Data entry • Preprocessing • Mean areal weighting schemes • Simulation and Forecasting - Three Separate Sub-systems • Operational Forecast System • Real-time hydrologic modeling and forecast generation • Calibration System • Parameter estimation/optimization and watershed simulation • Extended Streamflow Prediction (ESP) • Long-range probabilistic hydrologic forecasting

16. Operational Forecast System Current Conditions and Parameters Parameters Extended Streamflow Prediction Calibration System Historical Time Series Hydrologic Forecast System Components

17. Operational Forecast System Data Files Forecast Functions Data Entry Data Preprocessors Extended Streamflow Prediction System ESP Functions Parameter and State Files Models Calibration System Historical Data Simulation/ Optimization Programs Data Access, Utility, and Preprocessor Programs Data Files Data Files Hydrologic Forecast System Components

18. Hydrologic Modeling Structure • HydrologicTime Series • ComputationalOperations Input TimeSeries ComputationalOperation Rainfall-RunoffOperation Unit HydrographOperation Output TimeSeries

19. Operations Table Concept • Hydrologic Forecast System Hub • Operation - Any hydrologic input or output computation • Operations Table - List of computations and order for a segment • Segment - Group of operations performed as a unit • Operations Table Logic • Analogous to manual hydrology • Gives user freedom to select from available models • Easy to add new models • Compatibility between operational forecast, calibration, and ESP systems

20. Operations Table Concept (continued) • Variety of Models • Index • Conceptual • Others • Conceptual Model Advantages • Better probability of predicting extreme future events • Basin parameters can be adjusted to reflect land use changes • Potential application to problems other than just streamflow forecasts

21. Inputs MAP Snow Accumulation and Ablation Model Snow Model Temperature Index - Determines rain + melt from precipitation and temperature MAT + RAIM R/R Model Sacramento SMA, API, etc. Parameters Runoff Time Distributions Unit Hydrograph Instantaneous Discharges Mean Discharge Mean Discharge Computations Mean Daily Discharges Hydrographs Statistics Output Operations Table Concept

22. SNOW-17 Area A SAC-SMA Area A SNOW-17 Area B SAC-SMA Area B WEIGH-TS Area A + B (Runoff) UNIT-HG Area A+B to Point 1 STAGE-Q Point 1 (H Q) ADJUST-Q Point 1 STAGE-Q Point 1 (Q H) PLOT-TUL Point 1 LAG/K Reach 1-Reservoir SNOW-17 Area C SAC-SMA Area C UNIT-HG Area C to Reservoir ADD/SUB (Routed + Local) MEAN-Q (Inst Mean) STAGE-Q Point 2 (Tailwater Q) RES-SNGL Reservoir/Point 2 PLOT-TUL (Pool/Storage) PLOT-TUL (Inflow/Outflow) Operations Table Example

23. Hydrologic Forecast System Operations

24. Hydrologic Forecast System Operations (Continued)