Western Area Power Administration

2012 Interim Base-flow Proposal

June 12, 2012

Western requests base-flow releases from Flaming Gorge Dam be set so that flow in the Green River at 

Jensen is 1,100 cfs. Implementation of this request would require monitoring of Yampa River flows in 

order to adjust releases from Flaming Gorge Dam. Further, Western requests that base flow be revisited

in early July, once backwater topography data and updated hydrologic data are available. This request is

prudent based on current dry hydrologic conditions; is consistent with implementation of Flow and 

Temperature Recommendations for Endangered Fishes in the Green River Downstream of Flaming Gorge 

Dam (Flow Recommendations; Muth et al. 2000), the preferred alternative in the 2005 final 

environmental impact statement (FEIS; U.S. Department of Interior 2005), and the 2006 record of 

decision (ROD; U.S. Department of Interior 2006); and conserves water until real-time data are available 

to modify flows to maximize near shore habitat important for endangered fishes.

Based on the May 1st April – July inflow forecast for the Upper Green River (82% exceedence) and 

Yampa River (96% exceedence) basins, the hydrologic classification for 2012 spring peak flow was dry. 

Currently, hydrologic conditions do not appear to be improving, and it appears likely the classification 

for the summer base-flow period will remain dry. Western’s request for a base flow of 1,100 cfs at the 

Jensen gage is supported by the recommendation for dry years (900-1,100 cfs with up to 40% variation 

around the mean daily flow) in the Flow Recommendations and the FEIS. The extreme dry conditions in 

the Yampa River Basin and the Green River Basin trending solidly towards drier conditions warrant a dry 

classification and a conservative approach to determining base flows.

Compounding the need for a conservative approach is the implementation of the Study Plan to Examine 

the Effects of Using Larval Razorback Sucker Occurrence in the Green River as a Trigger for Flaming 

Gorge Dam Peak Releases (LTSP), a study plan to scientifically evaluate the effectiveness of modifying 

the timing of spring peak releases from Flaming Gorge Dam to coincide with the presence of larval 

razorback sucker (Larval Trigger Study Plan ad hoc committee 2012). Conditions this year, especially in 

the Yampa River Basin, resulted in spring peak flows in the Green River being primarily driven by

releases from Flaming Gorge Dam. To meet flow targets this year, five days of bypass release (up to 

7,400 cfs) was necessary, resulting in much higher releases than stated in the Flow Recommendations. 

The impacts of the increased volume of water required as a result of implementing the study plan are 

not understood at this time, especially in the dry conditions experienced thus far this year.

Creation of backwater habitat was a primary factor considered by Muth et al. (2000) in developing 

recommendations for base flows. Backwater habitat is especially important for larval and young 

Colorado pikeminnow (CPM). The importance of backwater habitat for early life stages of CPM was

apparent in survey data collected by the Recovery Program. In 2010, Argonne National Laboratory 

conducted a correlation analysis of factors affecting young CPM catch data collected by Badame et al.

(2009). They found surface area of backwaters was the best predictor of YOY Colorado pikeminnow 

catch rate (Figure 1; unpublished data), but area of backwater habitat was not correlated with 
magnitude of flow (Figure 2; unpublished data). Further, Tyus and Haines (1991) found an inverse 

relationship between size and abundance of young CPM and mean flow in August and September. 

Variability of sand bar topography, inherent in a complex river system such as the Green River, makes 

establishing an optimum base flow difficult. This difficulty is further evidenced in results reported by 

LaGory et al. (2009), where they found the relationship between backwater characteristics and 

discharge complex and variable from year to year. Establishing an optimum base flow this year may be 

especially difficult since it is a dry year following an unusually wet year in 2011. 

Muth et al. (2000) recommended base flows be tied specifically to hydrologic conditions (i.e., higher in 

wet years) and the magnitude of peak flows. However, they acknowledged uncertainty with their baseflow recommendations and the difficulty in establishing an optimum base flow due to unpredictable 

sediment processes and associated variability in sandbar topography from year to year. They advocated

for the collection of real-time biological and physical data each year and using this information to 

adaptively implement base-flow recommendations. Table 5.3 in Muth et al. (2000) lists elevation of 

sandbars in nursery areas as an example of real-time information to be considered when developing 

base-flow magnitude. 

Argonne National Laboratory will be collecting sandbar topography data beginning June 25, 2012, and 

these data and the resulting relationships between flow and backwater surface area, volume, and depth 

will be available by July 6, 2012. The availability of this information will provide a real-time 

understanding of the current physical conditions within the middle Green River allowing for 

establishment of a suitable base flow. Until these topographic data are available, it is prudent to 

establish an interim base flow that conserves water but also has been demonstrated to create 

backwater habitat. 

A review of topographic data from 2003 – 2008 indicated a flow of 1,100 cfs consistently created 

suitable backwater habitat (LaGory et al. 2009). While 1,100 cfs did not create the optimum surface 

area, it did create backwater area comparable to flows of 1,540 cfs (the maximum allowable in the Flow 

Recommendations in a dry year) without the risk of overtopping some backwaters as was observed in 

2003. Therefore, an interim flow of 1,100 cfs at the Jensen gage should be suitable until real-time 

topographic data become available. The base flow should be revisited and modified using available realtime topographic and hydrologic data in early July to establish appropriate base flows for the remainder 

of the base-flow period.

Western believes a sensible base flow for the duration of the base-flow period cannot be established at 

this time. We believe an interim flow of 1,100 cfs until early July is the most logical approach to 

determining base flows for 2012. This approach adheres to the Flow Recommendations, FEIS, and ROD;

is reasonable considering dry hydrologic conditions; and is supported by available scientific data. 
Figure 1. Relationship of mean backwater area to number of YOY Colorado pikeminnow captured in the 

Middle Green River derived from backwater topographic mapping conducted 2003-2009 (figure 

provided by Dr. Kirk LaGory, Argonne National Laboratory).

Figure 2. Relationship of flow to mean backwater area for the Middle Green River derived from 

backwater topographic mapping conducted 2003-2009 (figure provided by Dr. Kirk LaGory, Argonne 

National Laboratory).

R2 = 0.7206

-50

0

50

100

150

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250

300

350

0 500 1000 1500 2000 2500 3000

Number of CPM captured

Mean backwater area (m2)

R2 = 0.0592

0

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1000

1500

2000

2500

3000

0 500 1000 1500 2000 2500 3000

Mean backwater area (m2)

Flow (cfs)
Literature Cited

Badame, P., K. Creighton, T. Hedrick, L. Monroe, and K. Bestgen. 2009. Young-of-the-year Colorado 

pikeminnow monitoring. FY 2009 Annual Project Report, Colorado River Recovery Program 

Project Number 138.

LaGory, K. E., J. W. Hayse, and C. Weber. 2009. Relationships between flow and physical characteristics 

of backwater nursery habitats in the middle Green River, Utah. Report to the Upper Colorado 

River Endangered Fish Recovery Program, Project Number FR-BW-TOPO. Environmental Science 

Division, Argonne National Laboratory, Argonne, Illinois. 

Larval Trigger Study Plan ad hoc Committee. 2012. Study plan to examine the effects of using larval 

razorback sucker occurrence in the Green River as a trigger for Flaming Gorge Dam peak 

releases. Upper Colorado River Endangered Fish Recovery Program, Lakewood, Colorado.

Muth, R. T., L. W. Crist, K. E. LaGory, J. W. Hayse, K. R. Bestgen, T. P. Ryan, J. K. Lyons, R. A., and R. A. 

Valdez. 2000. Flow and temperature recommendations for endangered fishes in the Green 

River downstream from Flaming Gorge Dam. Upper Colorado River Endangered Fish Recovery 

Program, Lakewood, Colorado.

Tyus, H. M., and G. B. Haines. 1991. Distribution, habitat use, and growth of age-0 Colorado squawfish 

in the Green River Basin, Colorado and Utah. Transactions of the American Fisheries Society 

120:79-89.

U.S. Department of Interior. 2005. Operations of Flaming Gorge Dam final environmental impact 

statement. U.S. Department of Interior, Bureau of Reclamation, Upper Colorado Region, Salt 

Lake City, Utah.

U.S. Department of Interior. 2006. Record of decision operation of Flaming Gorge Dam final 

environmental impact statement. U.S. Department of Interior, Bureau of Reclamation, Upper 

Colorado Region, Salt Lake City, Utah.