Peak Flow Forecasts, June 1, 2011   www.cbrfc.noaa.gov


NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents


Introduction

NEW: Starting in May 2011, we now estimate, where possible, an instantaneous flow for each mean daily flow forecast. These instantaneous flows are estimated from a historical regression analysis at each point. For more information view the regression plots.

Streamflow varies dramatically over the course of the snowmelt season. To characterize the magnitude of a year with a single seasonal peak sometimes can be an oversimplification. Hydrographs (or graphs of mean daily flow versus time) for each site can be viewed by clicking on the site name. The hydrographs include an example high and low year alongside last year and this year.

River recreationists often ask what are the high and low years. Rankings of a sites peak flows can be viewed by clicking the site name below. Reservoir regulation plays a major role in determining observed peak flows. As would be expected, higher (but more short-lived) peaks are generally observed in the pre-regulatory era (before 1960).


Upper Colorado Peak Flow Forecasts

Prepared by: Alcorn, Cox, Nielson
2011 Forecast Exceedance Probability
Historic
Peak
Average
Peak
Flood*
Flow
2010
Peak
2010
Date
90% 75% 50% 25% 10% Normal time
of Peak
Issuance
Date
Observed
Peak
Observed
Date
Blue
Blue River
Mean Daily Flow 580 190 865 240 6/10 300 400 500 550 600 6/1 - 7/6 5/31
Dillon, Nr
Mean Daily Flow 1,160 540 1,350 530 6/10 800 900 1100 1200 1250 6/2 - 6/26 5/31
Snake
Montezuma, Nr
Mean Daily Flow 870 465 1,200 730 6/08 700 770 830 900 980 6/2 - 6/22 5/31
Tenmile Ck
Frisco, Nr
Mean Daily Flow 1,480 785 1,640 1,070 6/08 1150 1200 1350 1500 1700 6/1 - 6/22 5/31
Fraser
Winter Park
Mean Daily Flow 440 190 400 290 6/08 250 300 400 450 530 6/6 - 6/30 5/31
Granby
Mean Daily Flow 2,080 1,000 2,225 1,770 6/09 1400 1700 2100 2350 2600 5/3 - 6/17 5/31
Colorado
Kremmling, Nr
Mean Daily Flow 12,700 3,900 10,150 5,870 6/15 N/A N/A N/A N/A N/A 5/15 - 6/27 N/A N/A
Eagle
Gypsum, Blo
Mean Daily Flow 6,580 3,600 6,410 6,160 6/08 5500 5800 6400 7200 8000 6/1 - 6/21 5/31
Instantaneous Flow 6100 6400 7100 7900 8800
Colorado
Dotsero, Nr
Mean Daily Flow 20,800 9,425 17,000 13,700 6/09 16000 17000 19500 23000 28000 5/25 - 6/20 5/31
Instantaneous Flow 17000 18000 20000 24000 29000
Crystal
Redstone, Nr, Avalanche Ck
Mean Daily Flow 3,500 1,965 3,020 3,110 6/09 2500 2700 2900 3100 3300 5/29 - 6/22 5/31
Instantaneous Flow 2900 3200 3400 3600 3900
Roaring Fork
Glenwood Springs
Mean Daily Flow 11,800 6,150 16,800 8,710 6/11 9000 10000 11000 12000 13500 6/3 - 6/18 5/31
Instantaneous Flow 10000 11000 12000 13000 15000
Colorado
Cameo, Nr
Mean Daily Flow 38,000 17,500 25,350 23,600 6/09 27000 30000 36000 40000 44000 5/29 - 6/18 5/31
Instantaneous Flow 28000 31000 37000 41000 45000
Plateau Ck
Cameo, Nr
Mean Daily Flow 4,100 1,460 4,160 1,410 5/30 Peak Soon, See Daily Forecast 5/9 - 6/11 5/31
East
Almont, Nr
Mean Daily Flow 5,000 2,080 2,970 2,300 6/08 2600 2800 3200 3500 3800 5/28 - 6/17 5/31
Instantaneous Flow 2900 3100 3500 3900 4200
Nf Gunnison
Somerset, Nr
Mean Daily Flow 7,080 3,310 10,565 2,700 6/07 Peak Soon, See Daily Forecast 5/11 - 6/2 5/31
Surface Ck
Cedaredge
Mean Daily Flow 640 210 1,611 140 4/23 Peak Soon, See Daily Forecast 5/3 - 6/8 5/31
Gunnison
Grand Junction, Nr (see Notes Below)
Mean Daily Flow 23,200 9,660 19,556 7,400 5/19 Peak Soon, See Daily Forecast 5/3 - 6/12 5/31
Colorado
Co-ut Stateline, Nr
Mean Daily Flow 68,300 26,150 47,550 29,600 6/10 37000 41000 47000 51000 55000 5/22 - 6/16 5/31
Instantaneous Flow 38000 42000 48000 52000 56000
Dolores
Dolores
Mean Daily Flow 6,950 2,980 7,820 2,700 5/30 Peak Soon, See Daily Forecast 5/9 - 6/4 5/31
San Miguel
Placerville, Nr
Mean Daily Flow 2,740 1,310 3,040 1,500 6/07 Peak Soon, See Daily Forecast 5/26 - 6/23 5/31
Colorado
Cisco, Nr
Mean Daily Flow 69,500 28,800 59,500 30,300 6/10 38000 42000 49000 53000 58000 5/20 - 6/15 5/31
Instantaneous Flow 39000 43000 50000 54000 59000
Green
Daniel, Nr, Warren Bridge, At
Mean Daily Flow 5,620 2,975 N/A 2,190 6/10 3300 3600 4000 4200 4500 5/30 - 6/30 5/31
Instantaneous Flow 3400 3700 4100 4300 4600
New Fork
Big Piney, Nr
Mean Daily Flow 9,110 5,285 9,800 5,470 6/13 5000 5500 6000 6500 7000 5/31 - 6/24 5/31
Instantaneous Flow 5100 5700 6200 6700 7200
Green
Labarge, Nr
Mean Daily Flow 18,800 9,270 14,000 8,350 6/13 12000 13000 14000 15500 16500 5/30 - 6/24 5/31
Instantaneous Flow 12000 13000 14000 16000 17000
Green Rvr Wy, Nr
Mean Daily Flow 15,400 7,110 12,500 2,820 7/05 10000 10500 11500 12500 14000 5/23 - 7/11 5/31
Instantaneous Flow 10000 11000 12000 13000 14000
Hams Fork
Frontier, Nr, Pole Ck, Blo
Mean Daily Flow 2,000 825 1,800 635 6/11 1150 1300 1550 1750 2000 5/10 - 6/9 5/31
Instantaneous Flow 1200 1400 1700 1900 2200
Blacks Fork
Little America, Nr
Mean Daily Flow 6,970 2,440 5,000 4,070 6/15 Peak Soon, See Daily Forecast 5/2 - 6/27 5/31
Elk
Nr Milner
Mean Daily Flow 6,100 4,160 5,800 6,100 6/09 Peak Soon, See Daily Forecast 5/19 - 6/12 5/31
Yampa
Steamboat Springs
Mean Daily Flow 5,870 3,240 5,500 3,690 6/08 Peak Soon, See Daily Forecast 5/19 - 6/12 5/31
Maybell, Nr
Mean Daily Flow 24,400 10,475 21,000 11,500 6/10 Peak Soon, See Daily Forecast 5/13 - 6/10 5/31
Little Snake
Lily, Nr
Mean Daily Flow 13,400 4,745 13,000 5,540 6/16 Peak Soon, See Daily Forecast 5/5 - 6/12 5/31
Yampa
Deerlodge Park
Mean Daily Flow 32,300 13,955 17,000 17,000 6/11 Peak Soon, See Daily Forecast 5/11 - 6/6 5/31
Green
Jensen, Nr (see Note1 Below)
Mean Daily Flow 38,500 17,600 25,000 19,400 6/11 Peak Soon, See Daily Forecast 5/14 - 6/11 5/31
Rock Ck
Upr Stillwater Res
Mean Daily Flow 2,080 1,350 N/A 2,040 6/08 2800 3200 3600 4000 4300 5/25 - 6/20 5/31
Currant Ck
Currant Ck Res
Mean Daily Flow Peak Soon, See Daily Forecast 5/31
Strawberry
Strawberry Res
Mean Daily Flow Peak Soon, See Daily Forecast 5/31
Starvation Res, Duchesne, Nr (see Note4 Below)
Mean Daily Flow Peak Soon, See Daily Forecast 5/31
West Fork Duchesne
Vat Diverison, Blo (see Note4 Below)
Mean Daily Flow Peak Soon, See Daily Forecast 5/31
Uinta
Neola, Nr
Mean Daily Flow 3,000 1,640 5,600 2,230 6/06 2000 2300 2600 3100 3400 5/25 - 6/15 5/31
Instantaneous Flow 2900 3400 3800 4600 5000
White Rocks
Whiterocks, Nr
Mean Daily Flow 2,300 1,230 2,800 1,120 6/08 1300 1450 1550 1650 1800 5/10 -6/10 5/31
Instantaneous Flow 1800 2100 2200 2400 2600
Big Brush Ck
Vernal, Nr, Red Fleet
Mean Daily Flow Peak Soon, See Daily Forecast 5/31
Duchesne
Tabiona, Nr (see Note4 Below)
Mean Daily Flow 2,320 765 4,100 1,070 6/9 2350 2500 2800 3100 3350 5/15 - 6/15 5/31
Instantaneous Flow 2600 2800 3100 3400 3700
Duchesne, Nr, Knight Div, Abv (see Note4 Below)
Mean Daily Flow 4600 5000 5700 6100 6500 5/31
Randlett, Nr
Mean Daily Flow 11,500 2,755 7,400 2,920 6/08 9000 10000 11000 12500 13500 4/27 - 7/5 5/31
Instantaneous Flow 9300 10000 11000 13000 14000
White
Meeker, Nr
Mean Daily Flow 6,320 3,200 11,000 3,310 6/09 Peak Soon, See Daily Forecast 5/21 - 6/14 5/31
Watson, Nr
Mean Daily Flow Peak Soon, See Daily Forecast 5/31
Green
Green River, Ut (see Note1 Below)
Mean Daily Flow 47,200 22,560 47,000 24,200 6/11 Peak Soon, See Daily Forecast 5/18 - 6/16 5/31
Cataract Canyon (estimated)
Mean Daily Flow 116,700 51,350 N/A 53,400 6/11 79000 88000 100000 110000 121000 5/20 - 6/16 5/31
San Rafael
Green River, Nr
Mean Daily Flow 3,600 910 N/A 307 6/16 2300 2600 2800 3100 3500 5/17 - 7/16 5/31
Muddy Ck
Emery, Nr
Mean Daily Flow 515 205 N/A 160 6/10 Peak Soon, See Daily Forecast 5/19 - 6/18 5/31
Dirty Devil
Hanksville, Nr, Poison Spgs **
Mean Daily Flow 1,690 445 N/A 798 6/14 N/A N/A N/A N/A N/A 3/12 - 5/31 5/31
Escalante
Escalante, Nr ***
Mean Daily Flow 307 72 N/A 96 7/27 3/24 - 6/2 5/31 102 5/29
San Juan
Pagosa Springs
Mean Daily Flow 4,640 2,485 6,750 2,450 5/30 Peak Soon, See Daily Forecast 5/15 - 6/12 5/31
Animas
Durango
Mean Daily Flow 10,700 4,675 9,554 4,500 5/30 Peak Soon, See Daily Forecast 5/28 - 6/14 5/31
Farmington (see Note 2 Below)
Mean Daily Flow 11,000 4,900 8,810 4,000 5/31 Peak Soon, See Daily Forecast 5/31 - 6/15 5/31
San Juan
Bluff, Nr (see Note 1 Below)
Mean Daily Flow 15,600 7,340 33,838 4,300 6/01 Peak Soon, See Daily Forecast 5/21 - 7/4 5/31

Red=Forecast Above Flood Flow, Yellow=Forecast Above Historic Peak.
N/A = Not Available (Not a flood forecast point or no forecast procedure exists.)
* = Flood flow is for current year only and is an instantaneous value.
- = Exceedance value has already occurred during the current runoff season.
Note1 - Peak flow forecasts on the Green River below Flaming Gorge Reservoir are based on USBR planned regulation.
Note2 - Peak flow forecasts on the San Juan below Navajo Reservoir are based on USBR planned regulation.
Note3 - Peak flow forecasts on the Gunnison below Crystal Reservoir are based on USBR planned regulation.
Note4 - Peak flow forecasts account for CUWCD planned operations.
** = Runoff period March - June.
*** = Runoff period March - June does not include contribution from Boulder Creek.


Great Salt Lake Peak Flow Forecasts

Prepared by: Bernard
2011 Forecast Exceedance Probability
Historic
Peak
Average
Peak
Flood*
Flow
2010
Peak
2010
Date
90% 75% 50% 25% 10% Normal time
of Peak
Issuance
Date
Observed
Peak
Observed
Date
Bear
Utah-wyoming Stateline, Nr
Mean Daily Flow 2,980 1,610 3,675 2390 6/8 2800 3100 3500 3800 4100 5/22 - 6/14 5/31 890 5/16
Instantaneous Flow 3500 3900 4400 4800 5100
Logan
Logan, Nr, State Dam, Abv
Mean Daily Flow 2,450 985 1,355 852 6/8 1900 2100 2300 2500 2800 5/18 - 6/10 5/31 1050 5/16
Instantaneous Flow 2000 2200 2400 2600 2900
Blacksmith Fork
Hyrum, Nr, Up&l Dam
Mean Daily Flow 1,650 490 935 150 4/22 Peak Soon, See Daily Forecast 4/24 - 5/20 5/31 1140 5/16
Weber
Oakley, Nr
Mean Daily Flow 4,170 1,625 3,015 2600 6/8 2900 3200 3500 4000 4300 5/24 - 6/16 5/31 1200 5/16
Instantaneous Flow 3500 3800 4200 4800 5200
Chalk Ck
Coalville
Mean Daily Flow 1,790 600 1,340 535 6/14 1500 1700 2000 2200 2400 5/5 - 5/31 5/31 970 5/16
Instantaneous Flow 1700 2000 2300 2600 2800
Provo
Woodland, Nr (duchesne Tun. Regulated)
Mean Daily Flow 2,820 1,685 3,150 2820 6/8 2600 2900 3300 3600 3800 5/11 - 6/6 5/31 1030 5/16
Instantaneous Flow 3000 3300 3800 4100 4400
Little Cottonwood Ck
Salt Lake City, Nr
Mean Daily Flow 800 470 800 800e 6/8 660 700 800 860 950 5/23 - 6/20 5/31 174 5/16
Big Cottonwood Ck
Salt Lake City, Nr
Mean Daily Flow 980 430 800 700e 6/8 630 670 730 825 850 5/18 - 6/9 5/31 330 5/16
Mill Ck
Salt Lake City, Nr
Mean Daily Flow 153 65 155 60 6/9 100 105 110 120 140 5/18 - 6/10 5/31 60 5/23
Emigration Ck
Salt Lake City, Nr
Mean Daily Flow 164 55 130 25 5/24 Peak Soon, See Daily Forecast 4/11 - 5/19 5/31 110 5/29
Red Butte Ck
Fort Douglas At Salt Lake City
Mean Daily Flow 105 22 85 12 5/25 Peak Soon, See Daily Forecast 4/11 - 5/19 5/31 50 5/15
City Ck
Salt Lake City, Nr
Mean Daily Flow 322 90 210 70 6/7 230 250 280 310 340 5/12 - 6/1 5/31 87 5/17
Spanish Fork
Castilla, Nr (regulated)
Mean Daily Flow 5,000 1,455 2,695 640 7/2 Peak Soon, See Daily Forecast 5/12 - 6/1 5/31 1460 5/17
Sevier
Hatch
Mean Daily Flow 1,990 594 1,185 670 6/07 Peak Soon, See Daily Forecast 5/4 - 6/15 5/31 1120 5/10

Red=Forecast Above Flood Flow, Yellow=Forecast Above Historic Peak.
N/A = Not Available (Not a flood forecast point or no forecast procedure exists.)
* = Flood flow is for current year only and is an instantaneous value.
- = Exceedance value has already occurred during the current runoff season.


Lower Colorado Peak Flow Forecasts

Prepared by: G. Smith
2011 Forecast Exceedance Probability
Historic
Peak
Average
Peak
Flood*
Flow
2010
Peak
2010
Date
90% 75% 50% 25% 10% Normal time
of Peak
Issuance
Date
Observed
Peak
Observed
Date
Virgin
Virgin
Mean Daily Flow 10,600 780 5,083 1,310 4/22 3/13 - 5/4 5/31 1,900 5/9
North Fork Virgin
Springdale, Nr
Mean Daily Flow 2,820 570 5,514 709 4/22 4/10 - 5/15 5/31 1,450 5/9
Santa Clara
Pine Valley, Nr
Mean Daily Flow 393 65 N/A 89 6/08 100 4/25 - 5/25 5/31 94 5/28

Red=Forecast Above Flood Flow, Yellow=Forecast Above Historic Peak.
N/A = Not Available (Not a flood forecast point or no forecast procedure exists.)
* = Flood flow is for current year only and is an instantaneous value.
- = Exceedance value has already occurred during the current runoff season.


River Running Permits/Information



Definitions

Peak Flow
The peak flow forecast represents the maximum mean daily flow (the highest average flow for an entire day during the runoff season) at a point during the April through July period, unless otherwise noted. It does not represent the instantaneous peak (the maximum flow at a single moment). In the case of smooth snowmelt regimes (hydrographs), it may be acceptable to approximate one with the other. In Arizona, the normal snowmelt period is from February to May. Occasionally, heavy rainfall events can produce higher peak flows than the snowmelt peak flows. For verification and calibration purposes, the maximum mean daily flow during the February through May period was used regardless of the runoff source. The Average Peak and Normal Time of Peak (defined as the average date of peak plus/minus one standard deviation which should include approximately 70% of the peaks) for a given gage are all derived from 1971 through 2000 data whereas the Historic Peak is derived from the period of record, including the most recent years, after reservoir regulation began.

Forecast Probabilities
Peak flow forecasts are presented in terms of probabilities or, more specifically, exceedance probabilities. The forecast labeled "most probable" is actually the 50% exceedance level meaning there are equal chances of being below the value or above the value (i.e., 50 chances out of 100 of being exceeded). The other exceedance probabilities associate the likelihood of exceeding other levels. In general, a close bunching of the exceedance forecasts indicates low variability and that the user can have a high degree of confidence in the forecast information. Conversely, a large spread in the exceedance forecasts indicates high variability.

Modeling Techniques
The peak flow forecasts that follow have been derived using a combination of (1) physically-based conceptual models and (2) statistical regression models. The conceptual model is the National Weather Service River Forecasting System in the Ensemble Streamflow Prediction (ESP) mode. Since the conceptual model requires reservoir operation plans for up to five months into the future, ESP application is limited to basins where regulation is minimal (mostly in the headwater areas). The farther downstream a forecast point is, the more likely it is that a statistical regression was used between natural snowmelt runoff volume and the observed maximum mean daily flow to generate the forecast. Such an approach performs better when the correlation between regulated and unregulated flow is strong and is constant from year to year.


Additional Information

Flow extremes, Not Supply
Peak flow forecasts are fundamentally different than water supply volume forecasts. Although the watershed snowpack is a principal component in both analyses, peak flows are not a supply question at all. Rather, peak flows characterize runoff extremes by predicting maximum mean daily flow at a single point during the spring snowmelt season. This extreme is related to the water supply volume, but the relationship is not direct or constant from year to year. As such, peak flow forecasts contain much more uncertainty than water supply volume forecasts.

Regulated vs. Natural Flows
An even more fundamental limitation is that peak forecasts describe regulated (actual or observed) in-stream flow well into the future, something difficult to do considering the quantity and changing nature of diversions in the Colorado River and Great Basin watersheds. (Note: supply forecasts deal with hypothetical "natural" flow - that which would have resulted in the absence of regulation). The Colorado Basin River Forecast Center routinely forecasts regulated streamflow, but only for several days into the future. Further into the future the ability to forecast reservoir regulation becomes more limited.

Different Uses and Users
Peak flow forecasts are used for different purposes than water supply volume forecasts. Users of these forecasts would include river recreationists, flood control agencies, emergency service directors, wildlife managers and anyone interested in the combined effect of watershed yield and human regulation on the actual (observed) in-stream maximum mean daily flows at a site.

Flood Flows
The National Weather Service defines flood flow as the flow at which damage to structures begins to occur. Over-bank flow may occur but still be below the defined flood flow. Flood flows contained in this document change from year to year due to such channel processes as deposition and scouring. Therefore, the flood flows that follow should only be applied to the current runoff season. It should also be noted that they are instantaneous flows and not maximum mean daily flows.