1. 1 Initial Investigation Red River of the North Floods March, April 2009 OHD Mike Smith, Victor Koren, Ziya Zhang, Naoki Mizukami, Brian Cosgrove, Zhengtao Cui NCRFC Mike DeWeese, Andrea Holz, Brian Connelly, Jim Husaby

2. 2 3/28/2009 40.82 ft 4/16/2009 33.98 ft Observed Stage at Fargo, ND Flood Stage 18.0 ft Top of Levee 41.0 ft

3. 3 ‘typical NCRFC forecast’ Observed and Forecast Stages Red River at Fargo, ND. Water stored on surface or in frozen soil? Stage NCRFC: “Where did the water go?” March 28 This forecast verified well but dropped out early April 16 Observed stage NCRFC most concerned about the over-prediction of the second crest

4. 4 Hypothesis Sudden rise in air temperatures combined with rain March 20-24 melted the (record) snow pack, leading to major flooding. Some melt water ponded on the flat terrain, possibly blocked by frozen culverts Sudden severe drop in air temperature March 25 froze the ponded surface water As the frozen soil and ponded water thawed out: –the ponded water infiltrated into the soil –did not immediately appear in observed 2 nd crest –came out as baseflow (Mike DeWeese said it was a very long recession, if not a record). NCRFC: “Where did the water go?”

5. 5 Hypothesis Testing 1.Meteorological and field observations –Soil temperature (HPRCC) –Air temperature (HPRCC) 2.Experiments with SAC-HT and ponded water 3.Water balance simulations

6. 6 Stations from the High Plains Regional Climate Center 1. Meteorological and Field Observations Fargo Lisbon Fingal Ekre Leonard Wahpeton Oakes Wyndmere Sabin Britton Wild Rice River

7. 7 10 20 30 40 Air temp very cold, soil temp not affected Indicates soil possibly covered by water Sudden warm up, snow pack melts; then sudden refreezing Air temp very cold, soil temp affected 1.Meteorological and Field Observations Observed Air and Soil Temperature March and April 2009 Stage at Fargo, ft. March April Red at Fargo Stage

8. 8 2. Experiments with SAC-HT and Ponded Water Use point temperature data at Wahpeton, ND Run SAC-HT with three depths of ponded water at a point in hypothetical experiment. Note effects on soil temperature Note effects on frozen ground and percolation

9. 9 Water on the Soil Surface in SAC-HT Soil column Water on the surfaceLayer 0 Layer 1 Layer 2 Layer 3 Layer 0 does not affect the water supply to SAC-HT but changes the atmosphere-soil heat exchange, and as a result the soil freezing process 2. Experiments with SAC-HT and Ponded Water Layer 0 is normally at 0.58 porosity. ‘Fill’ this porosity with 3 levels of water: 2.6, 11.6, and 12.2 mm of water

10. 10 Discharge at Wahpeton USGS Gauge September, 2008 to June, 2009 Air temperature and soil temperature for 3 depths of ponded water 2. Experiments with SAC-HT and Ponded Water Month Discharge, cfs Month Temperature, C Red River Soil Freezing Analysis

11. 11 2. Experiments with SAC-HT and Ponded Water Red River Soil Freezing Analysis Month Wahpeton, ND. Ice in Layer 0 Ice Content, mm Upper Zone Saturation, % Sudden Warm-up

12. 12 Red River Soil Freezing Analysis: Second Crest 2. Experiments with SAC-HT and Ponded Water March - April Wahpeton, ND. Wahpeton Flow, cfs Rain/melt, mm Temperature, C

13. 13 Red River Soil Freezing Analysis: Second Crest March - April 2. Experiments with SAC-HT and Ponded Water Wahpeton, ND. Wahpeton Flow, cfs Upper zone saturation, % Ice Content, mm

14. 14 Red River Soil Freezing Analysis: Second Crest Percolation Total Runoff Surface Runoff The deeper the water/ice on surface, the more the soil remains thawed and therefore percolates more water: Very sensitive Less runoff with deeper layer of surface water Case of 12.2 mm of ponded water 2. Experiments with SAC-HT and Ponded Water Wahpeton, ND March - April Percolation, mm/hr Total Runoff, mm/hr Surface Runoff, mm/hr

15. 15 Preliminary Conclusions Soil temperatures dependent on surface water/ice Frozen water in the soil can have a large impact on percolation SAC-HT runs indicate that surface water could have percolated into the soil rather than running off into the channel 2. Experiments with SAC-HT and Ponded Water

16. 16 Next Steps with Soil Freezing Analysis Modify SAC-HT to input amount of surface water; currently hard coded. Run analyses over basins not just point

17. 17 3. Water Balance Simulations NCRFC recommended using Wild Rice River at Abercrombie, ND to illustrate problems –Major tributary to Red River above Fargo –Record flooding during event Method for initial analysis: –Extract RFC operational MAP, MAT time series for period October 1, 2008 to June 1, 2009 (done) –Run existing (no SAC-HT) RFC segments over period Oct. 1, 2008 to June 1, 2009; confirm that we’re getting same results as NCRFC (ongoing) –Note behavior of simulated snow pack and runoff. –Perform detailed water balance computations using NWSRFS WATERBAL operation; compute: Total precipitation: rain and snowfall Total evapotranspiration Change in storage Total runoff –Re-run with SAC-HT –Extend analyses to other basins above Fargo, ND.

18. 18 Wild Rice River Above Abercrombie, ND Fargo Abercrombie

19. 19 Finding Existing SAC-HT can be run now as a diagnostic tool to indicate frozen/ponded water at surface (must start further back in time to catch the dynamics)

20. 20 Acknowledgements We would like to thank Natalie Umphlett of the HPRCC for graciously providing access to their data