Peak Flow Forecasts, April 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 65 80 100 130 180 5/28 - 7/5 4/1
Dillon, Nr
Mean Daily Flow 1,160 505 1,770 955 7/20 150 200 250 300 400 5/27 - 6/25 4/1
Snake
Montezuma, Nr
Mean Daily Flow 870 435 2,080 790 7/02 150 170 200 250 350 5/31 - 6/18 4/1
Tenmile Ck
Frisco, Nr
Mean Daily Flow 1,480 760 1,640 1,060 6/18 250 300 370 450 550 5/27 - 6/17 4/1
Fraser
Winter Park
Mean Daily Flow 440 180 360 295 7/03 20 35 50 100 200 6/1 - 6/29 4/1
Granby
Mean Daily Flow 2,080 940 2,700 1,520 7/01 150 250 450 650 950 5/4 - 6/21 4/1
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 1200 1350 1700 2100 2800 5/27 - 6/16 4/1
Instantaneous Flow 1400 1500 1900 2400 3100
Colorado
Dotsero, Nr
Mean Daily Flow 20,800 8,700 17,000 17,500 6/08 2500 3000 3800 5000 7000 5/22 - 6/13 4/1
Instantaneous Flow 2700 3300 4100 5300 7400
Crystal
Redstone, Nr, Avalanche Ck
Mean Daily Flow 3,500 1,930 3,440 3,030 6/25 800 900 1100 1400 1700 5/25 - 6/18 4/1
Instantaneous Flow 910 1000 1300 1600 2000
Roaring Fork
Glenwood Springs
Mean Daily Flow 11,800 5,920 16,800 8,200 7/02 2000 2300 2800 3500 4500 5/29 - 6/23 4/1
Instantaneous Flow 2400 2700 3200 4000 5100
Colorado
Cameo, Nr
Mean Daily Flow 38,000 17,000 26,000 29,200 6/09 5000 6000 7700 10000 13000 5/24 - 6/12 4/1
Instantaneous Flow 5500 6600 8300 11000 14000
Plateau Ck
Cameo, Nr
Mean Daily Flow 4,100 1,470 4,160 2,550 6/08 400 550 750 1100 1500 5/5 - 6/8 4/1
Instantaneous Flow 550 720 960 1400 1800
East
Almont, Nr
Mean Daily Flow 5,000 2,000 2,980 2,580 6/08 600 700 850 1100 1300 5/21 - 6/11 4/1
Instantaneous Flow 620 730 900 1200 1400
Nf Gunnison
Somerset, Nr
Mean Daily Flow 7,080 3,120 11,400 4,020 6/08 1000 1200 1500 1900 2300 5/8 - 5/31 4/1
Instantaneous Flow 920 1200 1600 2100 2600
Surface Ck
Cedaredge
Mean Daily Flow 640 210 1,600 200 6/10 80 100 150 190 220 5/1 - 6/1 4/1
Instantaneous Flow 120 150 220 280 320
Gunnison
Grand Junction, Nr (see Notes Below)
Mean Daily Flow 35,200 8,890 19,510 14,800 6/09 1800 2000 2400 2800 3300 5/1 - 6/3 4/1
Instantaneous Flow 2400 2600 3000 3400 3900
Colorado
Co-ut Stateline, Nr
Mean Daily Flow 68,300 25,500 46,200 46,800 6/10 4500 6500 10000 13000 18000 5/19 - 6/11 4/1
Instantaneous Flow 5100 7100 11000 14000 19000
Dolores
Dolores
Mean Daily Flow 6,950 2,940 7,820 3,050 5/31 1200 1400 1600 1900 2200 5/6 - 5/30 4/1
Instantaneous Flow 1400 1600 1800 2200 2600
San Miguel
Placerville, Nr
Mean Daily Flow 2,740 1,260 3,040 1,430 6/08 600 700 800 900 1000 5/21 - 6/16 4/1
Instantaneous Flow 720 830 940 1100 1200
Colorado
Cisco, Nr
Mean Daily Flow 69,500 27,500 59,500 48,500 6/10 5000 7000 11500 15000 20000 5/16 - 6/12 4/1
Instantaneous Flow 5400 7500 12000 16000 21000
Green
Daniel, Nr, Warren Bridge, At
Mean Daily Flow 5,620 2,695 6,100 3,960 7/2 1600 1900 2200 2300 2500 5/27 - 6/28 4/1
Instantaneous Flow 1600 1900 2300 2400 2600
New Fork
Big Piney, Nr
Mean Daily Flow 9,110 4,730 8,850 7,750 7/03 3100 3400 4100 4800 5500 5/26 - 6/23 4/1
Instantaneous Flow 3200 3500 4200 4900 5700
Green
Labarge, Nr
Mean Daily Flow 18,800 8,000 11,500 13,000 7/4 5000 5800 7000 8000 9000 5/26 - 6/21 4/1
Instantaneous Flow 5200 6000 7200 8200 9200
Green Rvr Wy, Nr
Mean Daily Flow 15,400 5,790 11,050 9,620 7/19 2700 3800 5500 7000 8000 5/5 - 7/8 4/1
Instantaneous Flow 2800 3900 5600 7100 8200
Hams Fork
Frontier, Nr, Pole Ck, Blo
Mean Daily Flow 2,000 710 1,740 1,190 6/17 230 270 340 450 550 5/9 - 6/6 4/1
Instantaneous Flow 240 280 360 480 590
Blacks Fork
Little America, Nr
Mean Daily Flow 6,970 2,090 4,720 4,630 6/01 390 500 750 1200 1900 5/1 - 6/30 4/1
Instantaneous Flow 430 550 810 1300 2000
Elk
Nr Milner
Mean Daily Flow 7,000 3,865 5,750 7,000 6/08 1400 1500 2100 2500 2900 5/17 - 6/3 4/1
Instantaneous Flow 1800 1900 2500 2900 3300
Yampa
Steamboat Springs
Mean Daily Flow 5,870 3,070 5,930 4,970 6/08 1100 1300 1700 2100 2600 5/19 - 6/10 4/1
Instantaneous Flow 1400 1600 2000 2400 2900
Maybell, Nr
Mean Daily Flow 24,400 10,300 21,200 19,600 6/09 3200 3800 4800 6000 7000 5/12 - 6/5 4/1
Instantaneous Flow 3400 4000 5000 6300 7300
Little Snake
Lily, Nr
Mean Daily Flow 13,400 4,320 N/A 9,580 6/10 1500 1900 2300 2700 3400 5/3 - 6/4 4/1
Instantaneous Flow 1600 2100 2600 3000 3800
Yampa
Deerlodge Park
Mean Daily Flow 32,300 13,470 N/A 26,700 6/10 4600 5500 7000 8500 10000 5/11 - 6/4 4/1
Instantaneous Flow 4900 5800 7400 8900 10000
Green
Jensen, Nr (see Note1 Below)
Mean Daily Flow 38,500 16,990 23,900 31,300 6/12 9000 10000 11500 13000 14500 5/11 - 6/7 4/1
Instantaneous Flow 9300 10000 12000 13000 15000
Rock Ck
Upr Stillwater Res
Mean Daily Flow 2,090 1,225 N/A 2,033 6/25 620 700 850 1000 1100 5/17 - 6/13 4/1
Currant Ck
Currant Ck Res
Mean Daily Flow 654 302 N/A 511 6/09 90 110 120 150 230 5/3-5/23 4/1
Strawberry
Strawberry Res
Mean Daily Flow 2,770 900 N/A 1,222 6/09 150 190 240 320 430 4/25-6/7 4/1
Starvation Res, Duchesne, Nr (see Note4 Below)
Mean Daily Flow 2,010 560 N/A 1,350 5/29 220 250 280 330 410 4/28-6/14 4/1
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 4/1
Uinta
Neola, Nr
Mean Daily Flow 3,000 1,245 5,620 2,400 7/01 520 650 950 1100 1400 5/15 - 6/11 4/1
Instantaneous Flow 720 910 1400 1600 2000
White Rocks
Whiterocks, Nr
Mean Daily Flow 2,300 820 N/A 1,510 7/01 450 620 700 830 880 5/8 -6/14 4/1
Instantaneous Flow 560 810 930 1100 1200
Big Brush Ck
Vernal, Nr, Red Fleet
Mean Daily Flow 414 235 N/A 245 6/22 80 100 120 150 210 5/4-6/1 4/1
Duchesne
Tabiona, Nr (see Note4 Below)
Mean Daily Flow 2,810 925 3,100 2,810 6/17 140 220 280 430 550 5/14 - 6/12 4/1
Instantaneous Flow 190 280 350 510 650
Duchesne, Nr, Knight Div, Abv (see Note4 Below)
Mean Daily Flow 4,670 1,490 N/A 4,410 7/1 250 370 530 750 1100 5/17-6/20 4/1
Randlett, Nr
Mean Daily Flow 11,500 3,070 N/A 9,230 7/02 650 800 1100 1550 2500 4/29 - 6/28 4/1
Instantaneous Flow 1100 1200 1500 2000 2900
White
Meeker, Nr
Mean Daily Flow 6,320 3,040 8,030 5,480 6/08 1450 1650 2000 2200 2500 5/17 - 6/9 4/1
Instantaneous Flow 1600 1800 2200 2400 2700
Watson, Nr
Mean Daily Flow 8,160 2,815 N/A 4,980 6/20 1500 1700 2050 2300 2700 5/16-6/8 4/1
Green
Green River, Ut (see Note1 Below)
Mean Daily Flow 47,200 21,700 36,400 43,700 6/15 11000 13000 15000 17000 20000 5/16 - 6/11 4/1
Instantaneous Flow 11000 13000 15000 17000 20000
Cataract Canyon (estimated)
Mean Daily Flow 117,000 48,000 N/A 86,300 6/12 14000 18500 25000 31000 40000 5/17 - 6/12 4/1
San Rafael
Green River, Nr
Mean Daily Flow 3,600 810 N/A 2,330 6/28 110 170 260 420 750 5/6 - 7/9 4/1
Muddy Ck
Emery, Nr
Mean Daily Flow 515 182 N/A 331 6/18 50 70 90 105 135 5/18 - 6/10 4/1
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 4/1
Escalante
Escalante, Nr ***
Mean Daily Flow 307 73 N/A 102 5/30 30 40 50 70 90 3/13 - 5/21 4/1
San Juan
Pagosa Springs
Mean Daily Flow 4,640 2,460 2,240 6/08 1100 1300 1600 1800 2000 5/9 - 6/5 4/1
Instantaneous Flow 1200 1500 1800 2100 2300
Animas
Durango
Mean Daily Flow 10,700 4,575 9,555 5,120 6/06 2200 2400 2800 3300 3800 5/20 - 6/8 4/1
Instantaneous Flow 2400 2700 3100 3600 4200
Farmington (see Note 5 Below)
Mean Daily Flow 11,000 4,710 8,810 4,860 6/08 2300 2500 3000 3500 4100 5/20 - 6/9 4/1
San Juan
Bluff, Nr (see Note 2 Below)
Mean Daily Flow 15,200 7,340 33,838 4,300 6/01 6300 6600 7200 7500 7900 5/15 - 6/28 4/1
Instantaneous Flow 7300 7700 8300 8600 9000

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 7/1 810 870 1000 1170 1390 5/15 - 6/14 4/1
Instantaneous Flow 960 1000 1200 1400 1700
Logan
Logan, Nr, State Dam, Abv
Mean Daily Flow 1,870 950 1,355 1630 6/26 680 820 890 940 1130 5/16 - 6/9 4/1
Instantaneous Flow 790 920 990 1000 1200
Blacksmith Fork
Hyrum, Nr, Up&l Dam
Mean Daily Flow 1,530 445 935 1180 5/16 190 210 250 300 380 4/16-5/17 4/1
Instantaneous Flow 210 240 280 340 430
Weber
Oakley, Nr
Mean Daily Flow 4,170 1,645 2,510 3040 7/1 730 830 970 1150 1400 5/20-6/16 4/1
Instantaneous Flow 790 910 1100 1300 1600
Chalk Ck
Coalville
Mean Daily Flow 1,420 560 1,335 1070 5/17 160 210 300 420 540 5/10-6/3 4/1
Instantaneous Flow 170 230 340 480 620
Provo
Woodland, Nr (regulated)
Mean Daily Flow 2,820 1,795 3,150 2480 6/25 840 980 120 1490 1680 5/12-6/7 4/1
Instantaneous Flow 1000 1200 180 1700 2000
Little Cottonwood Ck
Salt Lake City, Nr
Mean Daily Flow 760 455 800 653 7/3 210 240 270 300 330 5/20-6/18 4/1
Big Cottonwood Ck
Salt Lake City, Nr
Mean Daily Flow 925 430 800 698 6/24 180 220 250 280 330 5/18 - 6/7 4/1
Mill Ck
Salt Lake City, Nr
Mean Daily Flow 153 57 155 110 6/25 25 30 35 40 50 5/13 - 6/12 4/1
Emigration Ck
Salt Lake City, Nr
Mean Daily Flow 164 46 130 80 5/30 15 15 20 25 30 4/14 - 5/19 4/1
City Ck
Salt Lake City, Nr
Mean Daily Flow 262 80 210 167 6/16 30 35 45 55 65 5/13 - 6/1 4/1
Sevier
Hatch
Mean Daily Flow 1,740 490 1,186 1,090 6/18 140 150 160 170 180 5/4-5/30 4/1
Instantaneous Flow 160 170 180 190 200

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 5/10 230 240 290 380 480 3/19 - 5/8 4/1
North Fork Virgin
Springdale, Nr**
Mean Daily Flow 3,000 530 6,091 1,470 5/10 160 170 210 280 340 4/2 - 5/14 4/1
Santa Clara
Pine Valley, Nr**
Mean Daily Flow 212 60 N/A 94 5/29 10 10 20 20 40 4/16 - 5/26 4/1

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.