BUILDING STRONG ® South Platte CWMS Model Missouri Basin Forecasters Meeting January 29, 2014 South Platte CWMS Model Missouri Basin Forecasters Meeting January 29, 2014 Brian Twombly, Omaha District, Corps of Engineers

BUILDING STRONG ® Corps Water Management System (CWMS)  Developed by the Hydrologic Engineering Center (HEC). Software that Interfaces: Data Acquisition Data Storage HEC-HMS (rainfall/runoff) HEC-ResSim (reservoir routing) RiverWare (river system) HEC-RAS (hydraulics) HEC-FIA (economic consequences)  HEC-RTS is the personal computer version of CWMS that interfaces all the models without the database connections.

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HEC-HMS  Three models were developed: Upper Basin Snow Upper Basin Rain Middle Basin Rain

BUILDING STRONG ® Upper South Platte -Two different basins: Rain and Snow -Gridded snow and air temp from CRREL and NOHRSC

BUILDING STRONG ® Mid South Platte - Requires an input at the Waterton gage either from the upper HMS or NWS forecast.

BUILDING STRONG ® HEC-ResSim  HMS inflows fed into ResSim  ResSim computes reservoir releases for: ► Chatfield ► Cherry Creek ► Bear Creek

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HEC-RAS  Uses outflow from ResSim in reaches downstream of the reservoirs.  HMS provides flows to other reaches.

BUILDING STRONG ® Model Development - GeoRAS DEM: 2 meter LiDAR data for core Denver Metropolitan area, obtained in meter LiDAR data for core Denver Metropolitan area, obtained in meter DEM outside LiDAR extents, provided by the district.10 meter DEM outside LiDAR extents, provided by the district. Centerline Development: Digitized from aerial imagery for South Platte River and the major contributing tributaries in the basin.Digitized from aerial imagery for South Platte River and the major contributing tributaries in the basin. Centerlines in Green.Centerlines in Green. Cross Section Geometry : Cross sections in Red.Cross sections in Red. Developed by RAS team.Developed by RAS team. Storage Areas in Blue.Storage Areas in Blue.

BUILDING STRONG ® HEC-FIA  Calculates flood damages and loss of life  Uses inundations calculated in HEC-RAS

BUILDING STRONG ® Data Needs  Forecasted Temperature Grids ► CRREL to provide grids from NOHRSC ► 3 days forecasted temperature ► Any other sources of grids?  Historical gridded temperature and precipitation ► Could be used to develop spaghetti plots and probabilistic forecasts.

BUILDING STRONG ® Data Needs  NWS Waterton Forecast ► 6 hour time step ► Could be used instead of running the upper HMS model.  How are the radar precipitation grids ground truthed?

BUILDING STRONG ® Questions Brian Twombly, P.E. (402)

BUILDING STRONG ® South Platte ResSim Simulations Sept 2013 Flood Simulation  Transposed rainfall grid for Sept 2013  Created new rainfall grid over reservoir watersheds  Developed hydrographs using 75% HMS models  Create a Sept 2013 ResSim simulation using HMS results

BUILDING STRONG ® South Platte ResSim Sept 2013 Simulation Transposed Rainfall Grid  HEC-MetVue, Gage Interp, ArcGis  Created a grid of circles with Excel and ArcGis  Transposed gridded rainfall with MetVue  Re-sampled gridded rainfall by average rainfall for each circle over the time period of the gridded rainfall dss file  Created a new gridded rainfall file with Gage Interp

BUILDING STRONG ® South Platte ResSim Sept 2013 Simulation

BUILDING STRONG ® Sept 2013 Simulation Cherry Creek Basin Storm Centering

BUILDING STRONG ® Sept 2013 Simulation Downstream Storm Centering