Peak Flow Forecasts, March 1, 2012   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, Smith, Nielson
2012 Forecast Exceedance Probability
Historic
Peak
Average
Peak
Flood*
Flow
2011
Peak
2011
Date
90% 75% 50% 25% 10% Normal time
of Peak
Issuance
Date
Observed
Peak
Observed
Date
Blue
Blue River
Mean Daily Flow 580 185 835 410 7/20 90 120 150 190 260 5/28 - 7/5 3/1
Dillon, Nr
Mean Daily Flow 1,160 505 1,770 955 7/20 200 250 350 450 550 5/27 - 6/25 3/1
Snake
Montezuma, Nr
Mean Daily Flow 870 435 2,080 790 7/02 200 240 290 370 480 5/31 - 6/18 3/1
Tenmile Ck
Frisco, Nr
Mean Daily Flow 1,480 760 1,640 1,060 6/18 350 450 550 700 850 5/27 - 6/17 3/1
Fraser
Winter Park
Mean Daily Flow 440 180 360 295 7/03 70 100 150 200 275 6/1 - 6/29 3/1
Granby
Mean Daily Flow 2,080 940 2,700 1,520 7/01 500 600 800 1100 1500 5/4 - 6/21 3/1
Colorado
Kremmling, Nr
Mean Daily Flow 12,700 3,850 10,180 9,480 6/27 N/A N/A N/A N/A N/A 5/18 - 7/4
Eagle
Gypsum, Blo
Mean Daily Flow 6,580 3,600 6,410 5,450 6/08 1500 1700 2300 3100 4200 5/27 - 6/16 3/1
Instantaneous Flow 1700 1900 2600 3500 4700
Colorado
Dotsero, Nr
Mean Daily Flow 20,800 8,700 17,000 17,500 6/08 4200 4700 5800 8200 12000 5/22 - 6/13 3/1
Instantaneous Flow 4500 5000 6200 8700 13000
Crystal
Redstone, Nr, Avalanche Ck
Mean Daily Flow 3,500 1,930 3,440 3,030 6/25 1100 1200 1500 1900 2300 5/25 - 6/18 3/1
Instantaneous Flow 1300 1400 1700 2200 2700
Roaring Fork
Glenwood Springs
Mean Daily Flow 11,800 5,920 16,800 8,200 7/02 2800 3200 4000 5000 6700 5/29 - 6/23 3/1
Instantaneous Flow 3200 3700 4500 5600 7500
Colorado
Cameo, Nr
Mean Daily Flow 38,000 17,000 26,000 29,200 6/09 8000 9000 11000 15000 21000 5/24 - 6/12 3/1
Instantaneous Flow 8600 9600 12000 16000 22000
Plateau Ck
Cameo, Nr
Mean Daily Flow 4,100 1,470 4,160 2,550 6/08 600 800 1000 1300 1900 5/5 - 6/8 3/1
Instantaneous Flow 780 1000 1200 1600 2300
East
Almont, Nr
Mean Daily Flow 5,000 2,000 2,980 2,580 6/08 800 900 1100 1400 1800 5/21 - 6/11 3/1
Instantaneous Flow 840 960 1200 1500 2000
Nf Gunnison
Somerset, Nr
Mean Daily Flow 7,080 3,120 11,400 4,020 6/08 1700 2000 2400 2900 3700 5/8 - 5/31 3/1
Instantaneous Flow 1800 2200 2700 3300 4300
Surface Ck
Cedaredge
Mean Daily Flow 640 210 1,600 200 6/10 120 150 200 260 310 5/1 - 6/1 3/1
Instantaneous Flow 170 220 290 380 450
Gunnison
Grand Junction, Nr (see Note 3 Below)
Mean Daily Flow 35,200 8,890 19,510 14,800 6/09 1200 2500 5400 7000 9000 5/1 - 6/3 3/1
Instantaneous Flow 1800 3100 6100 7700 9700
Colorado
Co-ut Stateline, Nr
Mean Daily Flow 68,300 25,500 46,200 46,800 6/10 10000 12000 16000 21000 30000 5/19 - 6/11 3/1
Instantaneous Flow 11000 13000 17000 22000 31000
Dolores
Dolores
Mean Daily Flow 6,950 2,940 7,820 3,050 5/31 1800 2200 2500 3000 3700 5/6 - 5/30 3/1
Instantaneous Flow 2100 2600 2900 3500 4400
San Miguel
Placerville, Nr
Mean Daily Flow 2,740 1,260 3,040 1,430 6/08 800 850 970 1150 1360 5/21 - 6/16 3/1
Instantaneous Flow 940 1000 1100 1300 1600
Colorado
Cisco, Nr
Mean Daily Flow 69,500 27,500 59,500 48,500 6/10 11500 13500 17500 23000 32000 5/16 - 6/12 3/1
Instantaneous Flow 12000 14000 18000 24000 33000
Green
Daniel, Nr, Warren Bridge, At
Mean Daily Flow 5,620 2,695 6,100 3,960 7/2 1750 2100 2500 2600 2900 5/27 - 6/28 3/1
Instantaneous Flow 1800 2100 2600 2700 3000
New Fork
Big Piney, Nr
Mean Daily Flow 9,110 4,730 8,850 7,750 7/03 3100 3700 4500 5000 6000 5/26 - 6/23 3/1
Instantaneous Flow 3200 3800 4600 5100 6200
Green
Labarge, Nr
Mean Daily Flow 18,800 8,000 11,500 13,000 7/4 5500 6500 8000 9000 10500 5/26 - 6/21 3/1
Instantaneous Flow 5700 6700 8200 9200 11000
Green Rvr Wy, Nr
Mean Daily Flow 15,400 5,790 11,050 9,620 7/19 3100 5000 7500 9000 10000 5/5 - 7/8 3/1
Instantaneous Flow 3200 5100 7600 9200 10000
Hams Fork
Frontier, Nr, Pole Ck, Blo
Mean Daily Flow 2,000 710 1,740 1,190 6/17 330 380 480 650 860 5/9 - 6/6 3/1
Instantaneous Flow 350 400 510 700 930
Blacks Fork
Little America, Nr
Mean Daily Flow 6,970 2,090 4,720 4,630 6/01 430 620 1030 1710 2600 5/1 - 6/30 3/1
Instantaneous Flow 470 670 1100 1800 2800
Elk
Nr Milner
Mean Daily Flow 7,000 3,865 5,750 7,000 6/08 2100 2350 2900 3700 4500 5/17 - 6/3 3/1
Instantaneous Flow 2500 2700 3300 4100 4900
Yampa
Steamboat Springs
Mean Daily Flow 5,870 3,070 5,930 4,970 6/08 1800 2000 2500 3200 3900 5/19 - 6/10 3/1
Instantaneous Flow 2100 2300 2800 3500 4300
Maybell, Nr
Mean Daily Flow 24,400 10,300 21,200 19,600 6/09 5000 6000 7500 9000 11000 5/12 - 6/5 3/1
Instantaneous Flow 5200 6300 7800 9400 11000
Little Snake
Lily, Nr
Mean Daily Flow 13,400 4,320 N/A 9,580 6/10 2300 2600 3400 4500 5500 5/3 - 6/4 3/1
Instantaneous Flow 2600 2900 3800 5100 6200
Yampa
Deerlodge Park
Mean Daily Flow 32,300 13,470 N/A 26,700 6/10 7500 8500 10500 13000 15500 5/11 - 6/4 3/1
Instantaneous Flow 7900 8900 11000 13000 16000
Green
Jensen, Nr (see Note1 Below)
Mean Daily Flow 38,500 16,990 23,900 31,300 6/12 12000 13000 15000 17500 20000 5/11 - 6/7 3/1
Instantaneous Flow 12000 13000 15000 18000 21000
Rock Ck
Upr Stillwater Res
Mean Daily Flow 2,090 1,225 N/A 2,033 6/25 650 750 900 1000 1150 5/17 - 6/13 3/1
Currant Ck
Currant Ck Res
Mean Daily Flow 654 302 N/A 511 6/09 90 110 120 170 270 5/3-5/23 3/1
Strawberry
Strawberry Res
Mean Daily Flow 2,770 900 N/A 1,222 6/09 170 220 300 400 590 4/25-6/7 3/1
Starvation Res, Duchesne, Nr (see Note4 Below)
Mean Daily Flow 2,010 560 N/A 1,350 5/29 260 270 300 350 430 4/28-6/14 3/1
West Fork Duchesne
Vat Diverison, Blo (see Note4 Below)
Mean Daily Flow 661 185 N/A 661 6/16 24 24 24 24 24 5/10-6/3 3/1
Uinta
Neola, Nr
Mean Daily Flow 3,000 1,245 5,620 2,400 7/01 520 650 950 1100 1500 5/15 - 6/11 3/1
Instantaneous Flow 720 910 1400 1600 2200
White Rocks
Whiterocks, Nr
Mean Daily Flow 2,300 820 N/A 1,510 7/01 450 620 780 920 1030 5/8 -6/14 3/1
Instantaneous Flow 560 810 1100 1300 1400
Big Brush Ck
Vernal, Nr, Red Fleet
Mean Daily Flow 414 235 N/A 245 6/22 110 150 180 200 250 5/4-6/1 3/1
Duchesne
Tabiona, Nr (see Note4 Below)
Mean Daily Flow 2,810 925 3,100 2,810 6/17 170 240 370 550 720 5/14 - 6/12 3/1
Instantaneous Flow 230 300 450 650 830
Duchesne, Nr, Knight Div, Abv (see Note4 Below)
Mean Daily Flow 4,670 1,490 N/A 4,410 7/1 330 450 650 1000 1350 5/17-6/20 3/1
Randlett, Nr
Mean Daily Flow 11,500 3,070 N/A 9,230 7/02 650 860 1300 2000 3100 4/29 - 6/28 3/1
Instantaneous Flow 1100 1300 1700 2400 3500
White
Meeker, Nr
Mean Daily Flow 6,320 3,040 8,030 5,480 6/08 1900 2000 2400 3000 3500 5/17 - 6/9 3/1
Instantaneous Flow 2100 2200 2600 3200 3800
Watson, Nr
Mean Daily Flow 8,160 2,815 N/A 4,980 6/20 1900 2000 2500 3100 3800 5/16-6/8 3/1
Green
Green River, Ut (see Note1 Below)
Mean Daily Flow 47,200 21,700 36,400 43,700 6/15 14500 16000 19000 23000 27000 5/16 - 6/11 3/1
Instantaneous Flow 15000 16000 19000 23000 28000
Cataract Canyon (estimated)
Mean Daily Flow 117,000 48,000 N/A 86,300 6/12 26000 29000 36000 46000 59000 5/17 - 6/12 3/1
San Rafael
Green River, Nr
Mean Daily Flow 3,600 810 N/A 2,330 6/28 150 260 420 650 1060 5/6 - 7/9 3/1
Muddy Ck
Emery, Nr
Mean Daily Flow 515 182 N/A 331 6/18 70 80 105 140 190 5/18 - 6/10 3/1
Dirty Devil
Hanksville, Nr, Poison Spgs **
Mean Daily Flow 1,690 445 N/A 380 6/20 N/A N/A N/A N/A N/A 3/18 - 6/6 3/1
Escalante
Escalante, Nr ***
Mean Daily Flow 307 73 N/A 102 5/30 30 40 60 80 100 3/13 - 5/21 3/1
San Juan
Pagosa Springs
Mean Daily Flow 4,640 2,460 2,240 6/08 1600 1800 2100 2400 2900 5/9 - 6/5 3/1
Instantaneous Flow 1800 2100 2400 2800 3400
Animas
Durango
Mean Daily Flow 10,700 4,575 9,555 5,120 6/06 2800 3200 3800 4600 5200 5/20 - 6/8 3/1
Instantaneous Flow 3100 3500 4200 5100 5700
Farmington (see Note 5 Below)
Mean Daily Flow 11,000 4,710 8,810 4,860 6/08 2900 3400 4000 4800 5400 5/20 - 6/9 3/1
San Juan
Bluff, Nr (see Note 2 Below)
Mean Daily Flow 15,200 7,340 33,838 4,300 6/01 6000 6800 7700 8500 9500 5/15 - 6/28 3/1
Instantaneous Flow 7000 7900 8800 9600 11000

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.
** = Runoff period March - June.
- = 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.
Note5 - Peak flow forecasts on the Animas at Farmington are affected by the Durango Pumping Plant.
*** = Runoff period March - June does not include contribution from Boulder Creek.


Great Salt Lake Peak Flow Forecasts

Prepared by: Bernard, Bender
2012 Forecast Exceedance Probability
Historic
Peak
Average
Peak
Flood*
Flow
2011
Peak
2011
Date
90% 75% 50% 25% 10% Normal time
of Peak
Issuance
Date
Observed
Peak
Observed
Date
Bear
Utah-wyoming Stateline, Nr
Mean Daily Flow 3,030 1,600 3,670 3030 7/1 870 980 1150 1360 1590 5/15 - 6/14 3/1
Instantaneous Flow 1000 1200 1400 1700 2000
Logan
Logan, Nr, State Dam, Abv
Mean Daily Flow 1,870 950 1,355 1630 6/26 690 810 950 1110 1450 5/16 - 6/9 3/1
Instantaneous Flow 800 910 1100 1200 1500
Blacksmith Fork
Hyrum, Nr, Up&l Dam
Mean Daily Flow 1,530 445 935 1180 5/16 240 270 350 450 560 4/16-5/17 3/1
Instantaneous Flow 270 310 400 520 640
Weber
Oakley, Nr
Mean Daily Flow 4,170 1,645 2,510 3040 7/1 760 870 1080 1340 1620 5/20-6/16 3/1
Instantaneous Flow 820 960 1200 1500 1900
Chalk Ck
Coalville
Mean Daily Flow 1,420 560 1,335 1070 5/17 180 240 360 510 650 5/10-6/3 3/1
Instantaneous Flow 190 270 410 580 750
Provo
Woodland, Nr (regulated)
Mean Daily Flow 2,820 1,795 3,150 2480 6/25 890 1050 1290 1530 1760 5/12-6/7 3/1
Instantaneous Flow 1100 1200 1500 1800 2000
Little Cottonwood Ck
Salt Lake City, Nr
Mean Daily Flow 760 455 800 653 7/3 210 250 300 340 390 5/20-6/18 3/1
Big Cottonwood Ck
Salt Lake City, Nr
Mean Daily Flow 925 430 800 698 6/24 200 230 280 340 410 5/18 - 6/7 3/1
Mill Ck
Salt Lake City, Nr
Mean Daily Flow 153 57 155 110 6/25 20 30 40 60 70 5/13 - 6/12 3/1
Emigration Ck
Salt Lake City, Nr
Mean Daily Flow 164 46 130 80 5/30 10 20 30 50 70 4/14 - 5/19 3/1
City Ck
Salt Lake City, Nr
Mean Daily Flow 262 80 210 167 6/16 40 50 60 80 90 5/13 - 6/1 3/1
Sevier
Hatch
Mean Daily Flow 1,740 490 1,186 1,090 6/18 180 240 300 430 490 5/4-5/30 3/1
Instantaneous Flow 200 270 330 470 530

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.
** = Runoff period March - June.
- = Exceedance value has already occurred during the current runoff season.


Lower Colorado Peak Flow Forecasts

Prepared by: Bender
2012 Forecast Exceedance Probability
Historic
Peak
Average
Peak
Flood*
Flow
2011
Peak
2011
Date
90% 75% 50% 25% 10% Normal time
of Peak
Issuance
Date
Observed
Peak
Observed
Date
Virgin
Virgin**
Mean Daily Flow 6,350 800 4,950 1,860 5/10 280 320 400 720 1110 3/19 - 5/8 3/1
North Fork Virgin
Springdale, Nr**
Mean Daily Flow 3,000 530 6,091 1,470 5/10 160 220 280 400 480 4/2 - 5/14 3/1
Santa Clara
Pine Valley, Nr**
Mean Daily Flow 212 60 N/A 94 5/29 10 10 20 40 50 4/16 - 5/26 3/1

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.
** = Runoff period March - June.
- = 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.