CBRFC Peak Flow Forecast Webinar
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Transcript of CBRFC Peak Flow Forecast Webinar
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CBRFCPeak Flow Forecast Webinar
April 9th, 2014
Greg Smith & Ashley Nielson
These slides: www.cbrfc.noaa.gov/present/present.php
Presentation are available at:
www.cbrfc.noaa.gov/present/present2014.cgi
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Today’s Presentation
Web Reference: www.cbrfc.noaa.gov click on peak map
• What is a Peak Flow and How to Interpret the Graphics
• Current Soil and Snow Situation Impacting Peak Flow Forecasts
• Peak Flow Forecasts• Spring Weather Impacts /
Weather Forecast
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What is a Peak Flow Forecast?• Maximum Mean Daily Flow due to snowmelt
• April-July Period• Probabilistic Forecasts
• Exceedence Probabilities -10%, 25%, 50%, 75%, 90%• Regulated flow - accounting for reservoirs and diversions
• Planned operations if known• Assumptions based on past operations
• Only forecast magnitude of peak not time of peak• ~70 forecast points• Will issue twice a month this year
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Instantaneous Peak Flow Forecasts• Based on the observed
relationship between maximum mean daily flow and maximum instantaneous flow.
• Only calculated for sites where there is a good correlation between the two.– Sites where heavy rains can
cause sudden, large peaks generally do not have a good relationship.
Dolores River @ Dolores, CO
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Where to Find Peak Flow Forecasts
• Map: – http://www.cbrfc.noaa.gov/gmap/gmapbeta.php?interface=peak
• List: – http://www.cbrfc.noaa.gov/rmap/peak/peaklist.php
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Green = Low probability of reaching flood flow
Red = High probability of reaching flood flow
Zoom to area of interest
Hover over point to see name.Click on point to get graph.
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Peak Flow Forecasts
Critical levels indicated in forecast distribution
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50%75%
90%
25%
10%
Issue Date
Last month…….
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Normal time of peak
Minimum peak of record
Max peak of record
010%
25%50%75%90%
Forecast Probabilities
Flood Flow
Bankfull Flow
Current year observed daily streamflow to date
Select to plot min and max year hydrographs
Select to plot all historical peaks
Forecast Issuance Date
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Select to plot min and max year hydrographs
Min Year
Max Year
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Select to plot all historical peaks
Historical Yearly Peaks
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Current Conditions
visitpinedale.org
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Well above Upper Colorado and well below Great Basin
Modeled Soil Moisture
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SNOW – As represented in the CBRFC hydrologic model on April 8th 2014
Percent of the 30 year model calibration
average as of this date
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Green River – LaBarge
Forecast: 12500 CFSAverage: 4730 CFSFlood: 11500 CFS
Last Year: 3800 CFS
50% ExceedanceForecast
1986 18800 CFS1986
18800 CFS 201113000 CFS
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Yampa – Steamboat Springs
Forecast: 4500 CFSAverage: 3070 CFSFlood: 5930 CFS
Last Year: 2550 CFS
50% ExceedanceForecast
2011 4970 CFS1996
3810 CFS
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Elk River - Milner
Forecast: 5000 CFSAverage: 3865 CFSFlood: 5750 CFS
Last Year: 3090 CFS
50% ExceedanceForecast
20085780 CFS
20055660 CFS
20117000 CFS
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Colorado - Cameo
Forecast: 20000 CFSAverage: 17000 CFSFlood: 26000 CFS
Last Year: 9540 CFS
50% ExceedanceForecast
198333800 CFS
200822500 CFS
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Green River – Green River, UT
Forecast: 24000 CFSAverage: 21700 CFSFlood: 36400 CFS
Last Year: 11500 CFS
Colorado – Cataract Canyon
Forecast:55000 CFSAverage:48000 CFSFlood:None
Last Year:23000Forecasts are 50% Exceedance Forecast
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Animas - Durango
Forecast: 4500 CFSAverage: 5780 CFSFlood: 9560 CFS
Last Year: 2580 CFS
50% ExceedanceForecast
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Yellowstone - Altonah
Forecast: 700 CFSAverage: 950 CFSFlood: 2120 CFS
Last Year: 440 CFS
50% ExceedanceForecast
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Logan River - Logan
Forecast: 970 CFSAverage: 950 CFSFlood: 1370 CFS
Last Year: 480 CFS
50% ExceedanceForecast
19991430 CFS
19841830 CFS
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Weber River - Oakley
Forecast: 1300 CFSAverage: 1650 CFSFlood: 2500 CFS
Last Year: 770 CFS
50% ExceedanceForecast
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Weber River - Oakley
Forecast: 1300 CFSAverage: 1650 CFSFlood: 2500 CFS
Last Year: 770 CFS
50% ExceedanceForecast
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Provo River - Woodland
Forecast: 1550 CFSAverage: 1790 CFSFlood: 2880 CFS
Last Year: 1150 CFS
50% ExceedanceForecast
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Time of Peak• Peak forecasts are meant to
be long range outlooks and do not forecast the time of peak.
• As the peak nears, or as flows near critical levels, the daily forecast hydrographs are the place to get up-to-date information.– Peak flow list may indicate
“Peaking Soon” or “Peak has Already Occurred”
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Peak Forecast Summary
Forecast distribution touches the flood level at:• Upper Green River in Wyoming (* exceeded at 50% forecast)• Yampa River headwaters (Elk River, Steamboat Springs)• Colorado River Headwaters (@ Stateline, above Cameo, Eagle River)• Gunnison River above Blue Mesa (East River)
Keep an eye on:• Logan River near Logan
• Procedures don’t exist everywhere *
Small tributaries in heavy snowpack areas likely to see bankfull or greater conditions
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Impact of spring weather
• Runoff characteristics are largely determined by the day-to-day spring weather.
– While large snow pack years increase chances for flooding, it is not an inevitability (dodged a bullet at many sites in 2011)
– Small snow pack years can flood with the right sequence of spring temperatures and with flows enhanced by precipitation.
– Rain events may play a larger role in the magnitude of the peak flow during very low snow years.
– Keep an eye on our web page / daily forecasts
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Upcoming Weather – Ridge begins to flatten – increased chances for precipitation
1
2
1 – Weak system moves across the southwest over the weekend2 – System sags southward into the area late in the weekend Additional chances for precipitation next week
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Web Reference: www.hpc.ncep.noaa.gov
Saturday 4/12 – Monday 4/14
Forecast Precipitation for this Weekend
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April 14th – April 18th April 16th – April 22nd
Temperature Outlook
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90 Day Outlooks
Precipitation Temperature
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Peak Flow Forecast Schedule
• Forecast updates planned for:– Twice Monthly (1st week & mid month) through early June.
• Upcoming Webinars: – Water Supply, May 6th, June 5th – all at 1 pm MDT– Peak Flow ~ Early May or as needed
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CBRFC Contacts• Basin Focal Points for Peak Flow (Available to
discuss forecasts: 801.524.5130)– Upper Colorado: Brenda Alcorn– Green: Ashley Nielson– San Juan / Gunnison: Greg Smith– Great Basin: Paul Miller– Virgin / Sevier: Tracy Cox