McPhee Release Update for Wednesday June 26, 2019
POSTED BY ERIC SPRAGUE ON JUNE 26, 2019
McPhee is currently releasing flows of approximately 1,200 CFS downstream.
- Releases are expected to remain at 1,200 CFS until tomorrow afternoon, Thursday June 27th, when they are expected to ramp down to 800 CFS, but no lower.
- Releases will remain at approximately 800 CFS into Friday June 28th and potentially into June 29th while McPhee finishes filling. The lower releases preceding the weekend will both allow McPhee to fill more quickly ahead of the weekend and increase the chances that flows of 1,200 CFS or more can run through the weekend, when they will be the most accessible to boaters.
- Once McPhee is full, releases will ramp up to the flow necessary to equalize total inflows and total outflows in the reservoir for the purpose of maintaining the reservoir’s water surface elevation at full, elevation 6924 FT. These release flows are currently unknown, but are expected to be between 900 and 1,400 CFS Sunday and going into next week. Inflows are still expected to dial up this weekend, in reaction to the warming weather, before turning down.
- From the moment McPhee fills – which is expected Friday or Saturday – until the spill ends, releases will commonly fluctuate due to diurnal shifts and unpredictable weather patterns similar to a more natural river hydrograph. Please see below for important information to help you understand the variability for this period.
- After the bump in inflows coming this weekend, it is expected that the final recession in the runoff will begin, and releases will follow the inflows down until the spill ends.
- When inflows decrease enough to bring releases down to 800 CFS, managers will trigger a sudden “drop” in releases of 200 CFS (from 800 to 600 CFS). This “step” in flows is intended as a signal to alert boaters downstream of the impending dropping flows, which may be more difficult to boat on and may herald the approaching end of the spill. This step will last approximately 24 hours – or until McPhee begins to lose storage – after which releases will again balance with inflows and diversions, and the reservoir will resume its process of remaining at full while ramping releases down to base flows. At this point, releases will continue downward unless inflows in McPhee force them to increase.
- Should releases spike above 800 CFS again after that point due to an unexpected increase in inflows, another “drop” signal like the first will be triggered.
- Please continue to check back on this site regularly for new updates. They are still expected to come primarily on Mondays and Thursdays; however, once McPhee reaches full, there won’t be much change to the message. Note that there will not be a new update post tomorrow, Thursday June 27th.
The following is more detailed information regarding how the spill will behave once the reservoir reaches full.
So far this year, releases from McPhee have been managed very closely to be as controlled and stable as possible, with standardized, measured changes following predictable ramping patterns. Once McPhee reaches full, releases will begin to follow reservoir inflows. Primarily, this means three things;
- First, that releases will follow a more natural hydrograph. Extended periods at set flows will be unlikely. Instead, flows will behave almost as if on an unmanaged river, reacting unpredictably to a combination of dynamic factors ranging from snow water content, coverage, and melt rates to solar radiation, temperature, precipitation, and transit loss. While reservoir operation will moderate some of these rapid changes, releases will still follow inflows as much as possible and will be less steady than they have been. Releases will fluctuate to follow reservoir inflows less the current diversions.
- Second, that releases will fluctuate on a diurnal cycle, with larger releases at night in delayed response to snowmelt during the day, and lower flows during the day resulting from the reduced snowmelt at night.
- And third, that releases will not necessarily follow the standardized ramping rates experienced so far this year. Changes may come at any time of the day, and will change at roughly the same rate the upstream river is changing.
There is a possibility that releases may “hover” at some flows below 800 CFS (i.e. 200 – 799 CFS) for short periods of time as the seasonal recession in inflows progresses. At low flows in this range, there are alternate small craft boating opportunities as represented on the American Whitewater website “Recommended minimum flows are 200 CFS for canoes/kayaks/inflatables” link below.
The primary goal of managing the releases this way is to fill McPhee and then keep it at full while ramping down. Because volume is intended to remain constant, there is a reasonable relationship which can be drawn between inflows and outflows in order to get an idea of what releases are about to do. In CFS,
“Dolores River Inflows” + “Other inflows” – “Irrigation Diversions” = “McPhee Releases”
“Dolores River Inflows” are forecasted by the Colorado Basin River Forecast Center (CBRFC) and can be viewed on the CBRFC website at https://www.cbrfc.noaa.gov/station/flowplot/flowplot.cgi?MPHC2. Please note that these flows are forecasts, and not at all guaranteed. They are updated daily and can vary substantially from day to day, especially if you’re looking more than about two days out.
“Other Inflows” is a catch-all value used to represent other sources of runoff into McPhee, e.g. House, Beaver, and Plateau creeks. This late in the season, this value is negligible, and can be treated as zero.
“Irrigation Diversions” is the total volume of water diverted from the reservoir to the project users in the Montezuma Valley. Currently, it is approximately 700 CFS, however there is some potential for it to increase during the next several days.
“Irrigation Diversions” and “Other Inflows” are running at approximately 700 CFS, so the releases will track at about 700 CFS less than the Dolores Gage (Real time Dolores Gage flows are at https://waterdata.usgs.gov/nwis/uv?09166500). Please note that these USGS readings do not look ahead like the forecasts mentioned above.
If you are watching the river inflows into McPhee to try and estimate what releases will be, please keep in mind; 1) that releases will not equal inflows – see the equation above, and 2) that it takes time for changes in releases to travel downstream. As a point of reference, in the past, it has taken approximately 20 hours at 800 CFS for changes in releases to be detected at the Slickrock gage, and it has taken even longer at lower flows. Please plan any trips accordingly.
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: https://dwr.state.co.us/surfacewater/data/detail_tabular.aspx?ID=MCPRESCO&MTYPE=STORAGE
Dolores below McPhee: https://dwr.state.co.us/surfacewater/data/detail_graph.aspx?ID=DOLBMCCO&MTYPE=DISCHRG
Slickrock Gage: https://waterdata.usgs.gov/nwis/uv?09168730
Bedrock Gage: https://waterdata.usgs.gov/nwis/uv?09171100
Bureau of Land Management: https://www.blm.gov/visit/dolores-river-srma
The BLM has a detailed boating map of the Dolores river posted on their website. Link below.
BLM Avenza Map page for the Dolores: https://www.blm.gov/documents/colorado/public-room/map/colorado-dolores-river-100k-boating-map-17×40
DRBA: https://doloresriverboating.org/
AW: https://www.americanwhitewater.org/
The following are links to the American Whitewater River Inventory pages for the lower Dolores River: