POSTED BY ERIC SPRAGUE ON MAY 22, 2019
The managed release for Memorial Day weekend has begun. Today, McPhee is releasing 400 CFS downstream as it ramps up to 1,200 CFS by the morning of Friday May 24th at a rate of about 400 CFS/day. The 1,200 CFS flows will be maintained through Friday, Saturday, Sunday, and Monday of Memorial Day weekend. On the morning of Tuesday May 28th, flows will ramp down to 800 CFS and will remain there through noon on Thursday May 30th, when releases will begin to ramp down to 200 CFS at the standard ramp-down rate of 100 CFS/day. This pause in the spill is a reaction to the lower-than-predicted inflows McPhee has been receiving as a result of the cold weather, and is planned in order to give the reservoir a chance to fill, as McPhee cannot simultaneously fill & spill on these current low inflows, and McPhee must be filled during the runoff season. When McPhee gets closer to full, we can better manage the forecasted inflow error, which is currently at +/- 40,000 AF. We have a 70% probability – based on current volumetric inflow forecasts – of having excess water later in June. The current 10 day forecast indicates below normal temperatures and high chances for rain, which pushes the “re-open” date to between June 9th – 16th, though that date is subject to updated forecasts and has not been confirmed yet.
We will continue monitoring conditions with the Colorado Basin River Forecast Center (CBRFC) and will continue to post updates as the forecast changes to give as much notice as possible, primarily on Mondays and Thursdays (this post on Wednesday May 22nd will serve as the post for Thursday May 23rd) with any new information and decisions.
Nominally, that completes today’s update; however, for those interested in learning more on the current decision sequence, please read on.
The May 1st forecast originally had more volume coming into McPhee than storage space available, so on May 3rd we tried to foreshadow releases starting before Memorial Day. Many people planned on that announcement. As we talked to the forecasters, we learned that the weather pattern of closed lows that made all this extra wet cool weather recently were highly unpredictable. By May 15th we saw the snow pack was going to hang in the mountains and that we would miss projected reservoir elevation targets, but accommodated Memorial Day anyway. About 190 KAF has come down already this season, and while we know water is still up there, we do not know if there is 160,000 AF left or 190,000 AF left or exactly when it will come down, both of which will determine how much excess water is available to spill. Therefore, we decided to continue with an announced spill over Memorial Day and some fish monitoring flows afterwards with the potential to have to shut down the spill after those monitoring flows. Since last Friday May 17th the Dolores River flows have dropped from 2,900 CFS to 1,000 CFS. Continuing the spill after the 30th would likely cause a loss in reservoir elevation. We will have to ramp down after May 30th. The 10 day weather forecast remains below average with chance of clouds & rain which can both slow the melt. When we get into some more predictable sunny weather and river inflows increase, which usually happens in June, we should be able to continue spilling any excess water.
Also, there has been a statement floating around about this year being at “300% of snowpack”, and this has caused some confusion. What this means is that, for this day of the year, May 22nd – when most of our SNOTELS have traditionally melted out to zero – we are three times as high as we have been on average for this day in previous years. It does not mean that the current remaining snow is a record amount compared to the traditional snowpack peak dates, which are around April 1st of most years. It only means that what snow we have is lingering longer than normal.
If you have questions, the best way to address DWCD is through the “Contact” page of this website. Otherwise you can try calling 970-882-2164 extensions 5, 1 or 6.
Dolores Gage: https://waterdata.usgs.gov/nwis/uv?09166500
McPhee Elevation & Capacity: http://www.dwr.state.co.us/SurfaceWater/data/detail_tabular.aspx?ID=MCPRESCO&MTYPE=ELEV
Dolores below McPhee: http://www.dwr.state.co.us/SurfaceWater/data/detail_graph.aspx?ID=DOLBMCCO&MTYPE=DISCHRG
Slickrock Gage: https://waterdata.usgs.gov/nwis/uv?09168730
Bedrock Gage: http://waterdata.usgs.gov/nwis/uv?09171100