Colorado River Storage Project
Fontenelle Working Group
August 22, 2013
This meeting was held at the Joint Powers Water Board in Green River, Wyoming. See below for a list of parcipants.
The purpose of working group meetings (held in April, and August) is to inform the public and other interested parties of Reclamation's current and future operational plans and to gather information from the public regarding specific resources associated with Fontenelle Reservoir. In addition, the meetings are used to coordinate activities and exchange information among agencies, water users, and other interested parties concerning the Green River.
Heather Patno called the meeting to order at 10:00 a.m. with 17 present (see signup sheet for attendance). Presentations were given in the following order: Ashley Nielson, the National Weather Service Colorado River Forecast Center (CBRFC) followed by Heather Patno, Bureau of Reclamation. Before starting, all present introduced themselves and their affiliations.
Ashley Nielson with the Colorado River Basin Forecast Center in Salt Lake City provided a review of 2013 precipitation, temperature, snow pack, and streamflow conditions. She also characterized the April-July water supply forecast performance, and briefly discussed preliminary water supply and climate forecasts for WY 2014.
October, December, April and July monthly precipitation were above average. All other months had much below average precipitation. As a result, seasonal precipitation from October 2012 through July 2013 was below average, and amounted to only 70 to 90 percent of normal over the basin as a whole.
In contrast to the warm spring observed in 2012, March and April temperatures in 2013 were below normal. May temperatures were very close to normal. Despite being relatively cool, both April and May featured several consecutive days with above normal temperatures. In June, temperatures were well above normal.
Snow water equivalent (SWE) for the Green River above Fontenelle was 75 percent of median peak on April 1 (median peak date). In contrast to the spring of 2012, SWE continued to increase through April as a result of above normal precipitation and below normal temperature in the month of April. Snowpack peaked on April 24th at 89% percent of the median peak. Runoff primarily occurred during May, and observed snow water equivalent was reduced to zero during the first week of June.
Streamflows measured in the Green River at Warren Bridge and Pine Creek above Fremont were close to “normal” (25th-75th percentile class) from April through June. Flows then declined to “below normal” (10th-24th percentile class) in July and were “much below normal” (lowest 5th percentile) in August. Flows in the Green River near La Barge were “normal” in May, but were reduced to “much below normal” from June through August.
Water Supply Forecast Performance:
The April 1st most probable (50% exceedance probability) water supply forecast was 405,000 acre-feet (AF) which is 56% of average with a range of 250,000 to 600,000 AF. In the April 16 mid-month forecast update, the most probable forecast increased to 435,000 AF (60% of average) due to above average precipitation in April. However, subsequent months were warm and dry, such that the observed water supply volume from April through July was 317,000 AF (44% of average), and fell within the lower portion of the forecasted range.
In contrast, the observed water supply volume in the the upper basin (Green River at Warren Bridge) was consistent with the April 1st most probable forecast. The CBRFC plans to review the model features between Warren Bridge and Fontenelle Reservoir in an effort to improve forecasted reservoir inflows.
Weather and Climate Forecasts
ENSO conditions are currently neutral and are forecast to remain neutral in WY 2014. Long range climate forecasts continue to show increased chances for above normal temperatures and equal chances of below or above normal precipitation through early 2014. As a result, forecasted fall inflows to Fontenelle are below average, ranging from 39% of average in August (30,000 AF) to 62% of average in October (30,000 AF).
Heather Patno presented the current conditions at Fontenelle Reservoir and described operations during WY 2013, as well as those anticipated for WY 2014. Fontenelle Reservoir is currently 68% full, which correlates to 14.8 ft below maximum reservoir elevation (6506.0 ft). The current release is 700 cfs, and the average daily inflow is 450 cfs.
The release plan based on the April mid-month forecast of 435,000 AF was for steady 850 cfs releases through May, with an increase to approximately 1,050 cfs for the remainder of the summer through the winter. However, the actual April-July water supply volume of 317,000 AF (44% of average) amounted to 27% less than the April mid-month forecast. As a result, releases were reduced from 850 cfs to 800 cfs on May 15th, and were further reduced from 800 cfs to 700 cfs on July 25th. From April through August, the observed pool elevation has been between the reasonable minimum and most probable elevations presented in the April forecast. Reservoir releases are expected to remain at 700 cfs through the fall and winter.
Forecasted fall inflows WY 2014 range from 495,000 AF (46% of average) to 1,590,000 (147% of average). The most probable water supply forecast is 885,000 AF (82% of average).
Fontenelle Reservoir is scheduled for annual maintenance and inspection from October 15th through October 23rd. The reservoir will bypass water during this time.
As discussed during the April 25th meeting, the outlet works stilling basin was recently dewatered in order to conduct concrete repairs. According to Mark Neeley, the stilling basin work was completed with no surprises encountered.
Reclamation’s Standard Operating Procedures (SOPs) for Fontenelle reference a 300 cfs minimum release requirement, but staff have been unable to locate a contractual agreement that verifies the requirement and/or specifies its purpose. JPWB staff will check for documentation related to the 300 cfs minimum flow requirement.
Given the addition of semi-permanent rock features, operators believe that the minimum release rate under which the Jim Bridger Power Plant pump station can continue to operate is 400-450 cfs.
As of this year, the Colorado Basin River Forecast Center (CBRFC) began reporting snow pack conditions relative to the historic median, rathan than the historic mean. The mean SWE time series was characterized by skewed tails. In addition, the median better captures the timing and volume of peak SWE. Note that use of the median is limited to snowpack; water supply values continue to be reported relative to the historic mean.
Two years ago the CBRFC began using the 1981–2010 as the historic period of reference, and the forecast models are now calibrated to this period, rather than 1971-2000. These adjustments did not otherwise impact the methodology of forecasted water supply volumes or the 24-month study.
Reclamation noted that operations were changed several years ago to maintain an additional 5 ft of storage (6468 ft vs. 6463 ft) in order to conserve the State’s water supply, particularly in drought years. This change was a result of discussion between Mike Besson/Wyoming Water Development Commission, Ed Vidmar/BOR, and Rick Clayton/BOR.
Attendees asked Reclamation to identify scenarios in which the proposed operations would change, and more specifically, what conditions might lead to a reduction in releases. Reclamation noted that, while inflow volumes were similar between 2007 and 2013, current pool elevation is higher than it was in 2007, allowing for greater operational flexibility. Given the current inflow forecast, operators will maintain a 700 cfs release through February 2014. Proposed operations will be reviewed as observed and forecasted hydrology evolve, but are not expected to change. In particular, releases are not likely to be reduced below 700 cfs unless conditions result in pool elevation dropping at a rate of 1.0 foot per day or more.
Despite low flows and warm temperatures, no algal blooms or fish kills have been reported in 2013. This is in contrast to 2007, when algae was abundant and resulted in fish kills. It was noted that temperature and dissolved oxygen data for the Green River and at the dam would be useful during low flow conditions. Seedskadee NWR may follow up with USGS to identify any existing data, and to determine the feasibility of collecting additional data.
A request was made for fall reservoir operations to consider brown trout and Kokanee salmon spawning. There are three runs for Kokanee salmon from late August through October. Any reduction in the river level during/after the three runs would be detrimental to the eggs.
The next meeting date was set for 10:00am on Wednesday, April 23, 2014, at the Seedskadee Wildlife Refuge in Green River, WY.
Fontenelle Working Group Meeting Minutes:
|Heather Patno||Bureau of Reclamation, Salt Lake City|
|Kirk Jensen||Bureau of Reclamation, Fontnelle Dam|
|Lee Traynham||Bureau of Reclamation, Provo|
|Mark Neeley||Bureau of Reclamation, Salt Lake City|
|Rick Clayton||Bureau of Reclamation, Salt Lake City|
|Ashley Nielson||Colorado Basin River Forecast Center|
|Aldena Cherva||Joint Powers Water Board|
|Barry Cook||Joint Powers Water Board|
|Ben Bracken||Joint Powers Water Board|
|Bryan Seppie||Joint Powers Water Board|
|Robin Toone||Joint Powers Water Board|
|Mike Meyer||Pacificorp, Jim Bridger Power Plant|
|Tom Koerner||Seedskadee NWR|
|Nick Walrath||Trout Unlimited|
|Erik Roosa||City of Green River|
|Doug Stewart||City of Green River|
Email comments/inquires to: ResourceMgr@usbr.gov