Flaming Gorge Technical Working Group

July 7, 2012, 10:00am

Conference Call Record

Attending: 

Fish and Wildlife Service: Kevin McAbee, 

UCRIP – Tom Chart, Jana Mohrman, Kevin Bestgen

Reclamation – Katrina Grantz, Malcolm Wilson, Beverley Heffernan, Dave Speas, Peter 

Crookston, Ed Vidmar

Western – Jerry Wilhite, Clayton Palmer

Argonne National Labs – Kirk LaGory

Agenda:

• Review 2012 spring larval entrainment findings [Reclamation, Speas]

• Review updated hydrology [Reclamation, Grantz]

• Review updated backwater habitat data [Argonne, LaGory]

• Discussion [FGTWG members] 

• FGTWG decision on recommendation to Reclamation 

Overview:

The primary purpose of the call was to discuss flows during the Early Base Flow Period 

(June-Sept 30th). Katrina Grantz of Reclamation, acting FGTWG chair, filling in for 

Heather Hermansen, lead the meeting. 

Hydrology Discussion:

Katrina Grantz reviewed spring and summer/fall basin hydrology and Flaming Gorge 

reservoir operations information. The July forecast for unregulated inflow to Flaming 

Gorge during the April – July season is 540kaf (~84% exceedence) and is trending down. 

This forecast corresponds to the lower end of Moderately Dry hydrologic classification. 

Flows on the Yampa are extremely low, (3rd percentile) at ~60cfs. For the current 

Moderately Dry hydrologic classification, the 2000 Flow and Temperature 

Recommendations recommend flows at Jensen in the range 1,100cfs-1,500cfs. Based on 

hydrology, Katrina recommended a target baseflow near the lower end of the moderately 

dry hydrologic classification (in the range of 1,100 to 1,300cfs at Jensen). Katrina 

presented 3 operations scenarios: targeting (1) 1,100cfs at Jensen, (2) 1,300cfs at Jensen, 

and (3) 1,500cfs at Jensen, using the current forecast for the Yampa. Jana Mohrman

noted that Elkhead is releasing approximately 40cfs and likely will contribute 

approximately that much for the remainder of the season.

Spring 2012 Larval Entrainment Findings:

Dave Speas provided an overview of field observations during and after the Larval 

Trigger Study. Dave noted that the study was a success in term of the great coordination 

and execution to bring water in a short amount of time to boost water in Stewart Lake. 

The goal was to entrain razorback sucker larvae during the spring peak. The execution 

was very good and, in terms of meeting the entrainment goals, was huge success. 

Unfortunately, many of the wetlands that connected last spring experienced very high 
2

evaporation and evapotranspiration and nearly or essentially dried up this year, and 

although there aren’t direct observations of dead endangered fish, it was clear there were 

widespread fish kills. So it appears the LTS was successful in implementing larval 

trigger flows (entrainment occurred, timing was apparently great), but that there wasn’t 

sufficient volume of water entrained to sustain the wetland habitats through the end of 

June. FGTWG discussion of specific wetlands followed. Members discussed that Matt 

Breen indicated that he observed nearly 100% fish kill in Stewart Lake before end of 

June and that Aaron Webber noted that results downstream were also very dismal. The 

group noted that these results are a good data point for results in a low water year. The 

group noted that larval entrainment was aimed at razorbacks and that the goal now is for 

habitat for pikeminnow.

Review Updated Backwater habitat data:

Kirk LaGory provided and overview of recent backwater survey results. The group 

evaluated relationships between flow and surface area, depth and volume (indicators of 

habitat). The group reviewed both individual backwater data and the total values for all 

backwaters. Kirk noted that the relationship between flow and habitat is fairly different 

than what was seen in 2011 (e.g., Backwater 5 last year was very signification player... 

not so much this year). Despite lack of big peak flow, still have significant differences 

between flow-volume, depth, area. Kirk noted that we have decent depth even at lower 

flows this year. He described that surface area is a very important variable for habitat 

and that the flow-surface area relationship is comparable to last year, but different in 

some ways. He also noted that surface area is generally increasing with flow up to 

around 1700cfs, above which there is a drop off of surface area. 

Discussion

The group discussed which flow regimes would be best for fish and habitat given the 

current hydrology. Much of the discussion focused on whether and how much flows 

could be enhanced during the summer months, and what that would mean for flow and 

habitat during the winter months. The group discussed the question of whether it is 

better to have high backwater habitat (and flows) right now and then slope down through 

the fall and down to winter. Kevin Bestgen stated that, in terms of flows, the highest 

value for the fish is in the summer to help small fish grow, producing better survival rates 

going through fall and winter. He noted that historically/naturally, this is how things 

occurred. Kevin McAbee expressed a desire to start out high (1500+ cfs) now and hold it

for a month and then end up at 1500cfs near the end of September. He pointed to 2002 

data, when the hydrology was very low and there were low survival rates. Katrina Grantz 

noted that due to the dry hydrology this year higher flows in summer will require lower 

flows in winter in order to meet spring reservoir storage targets. She also noted that the 

forecast is trending down and conditions are likely to get drier than is currently modeled.

After biology, backwater habitat and hydrology discussion, each FGTWG member 

weighed in on what type of flows he or she could support as a final FGTWG 

recommendation to Reclamation management. 
3

Dave Speas (Reclamation) was in support of flows up to and including 1500cfs for the 

early summer, if we were to exceed 1500 at Jensen, he would not advocate doing it for 

very long. Katrina Grantz said she could support higher flows earlier in the Base Flow 

season, if these releases were backed off later in late August and September, 

recogninzing this will result in flows perhaps as low as 800 and 850cfs later in the fall 

and winter. Ed Vidmar expressed concern about the dry hydrology and that it is trending 

drier and that we likely won’t get the inflow currently projected for the fall and winter 

months.

Kevin McAbee (FWS) said he would like to go over 1500 even if for a little bit right 

now, would like it for a few weeks to a month. He said he wouldn’t like to see flows 

below 1400 before Sept 30th, but was willing to give up a little bit as we got closer.

Jerry Wilhite (Western) said he would like to see flows it higher during the summer, as 

close to 1500 while we can, but doesn’t want to sacrifice the winter. He mentioned he 

did not want to see 1500 in through September 30th and then drop directly to 800cfs on 

Oct 1st. Jerry is in support of ramping down throughout the whole month of September 

rather than a drop off. 

Recommendation:

After discussion regarding biology and hydrology, the group agreed to propose to 

Reclamation management the following base flow targets for the months of July, August 

and September:

Targets at Jensen, UT:

July: 1,500cfs 

Aug: 1,500cfs

Sep: 1,300cfs

There were no dissenting votes in the group’s final proposal. Concern was expressed by 

Reclamation regarding the relatively high proposed releases based on the dry hydrology 

this year. Concern was also expressed by FWS that flows at or above 1,500cfs are very 

important during the summer months for fish. There was final agreement by Western, 

FWS and Reclamation to stay close to 1500 for July and August and ramp down to 

1,300cfs in September to result in a more gradual transition to winter base flows 

beginning in October.

The group agreed that enhanced base flows during the summer season are very important 

to growth and survival rates of smaller fish, even if it means trading lower base flows in 

the fall and winter months for higher base flows during the summer months. There was a 

general understanding that the proposed base flows for the summer months would likely 

result in base flows near 800-850 cfs during the Oct-Feb months.

Based on this hydrology and the need for Reclamation to get as near to the 6027 elevation 

target by March 1st, the target baseflow for the entire base flow season (through March 

1st) is 1,100cfs. The proposed summer targets exercise the + or - 40% variability from 
4

the overall target base flow. For the winter base flows, it is anticipated that the 

recommended targets will exercise the + or – 25% variability (winter targets have not 

been explicitly discussed in terms of a proposal to Reclamation management.)

Next Steps:

The FGTWG chair (currently, Katrina Grantz, acting for Heather Hermansen) will put 

forth to Reclamation management the FGTWG proposed Early Base Flow targets. The 

FGWTG will be informed of Reclamation’s final decision. 

Because the current target at Jensen, UT is already 1,500crfs, no immediate changes 

would need to be made to operations at Flaming Gorge Dam. Flows on the Yampa will 

continue to be monitored and releases will continue to be adjusted as needed.