McPhee Release Update for Monday July 1, 2019
JULY 1, 2019
McPhee is currently releasing flows of approximately 1,500 CFS downstream as releases decrease following the diurnal runoff pattern.
- As of Friday June 28th, McPhee has reached full.
- Releases are varying as necessary to equalize total reservoir outflows (including diversions) with total inflows in order to maintain McPhee’s water surface elevation at full, or 6924 FT.
- Because releases are following the river, it isn’t known with certainty what releases will be through the end of the spill other than that they will vary regularly and trend downwards. Given today’s Dolores River inflow, releases should stay above 1,000 CFS through July 4th or a little longer, but this cannot be guaranteed. On a normal recession, daily average inflows can be expected to drop by a couple hundred CFS per day until the snowpack runs out. Check river gages and this site regularly before you leave on a river trip.
- 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 – which began this weekend and continues into this work week as a result of the clear skies and warming trend – it is expected that the final recession in the runoff will begin within the next couple of days, and releases will follow the inflows down until the spill ends.
- Managers are no longer planning on triggering the sudden 200 CFS drop when releases recede to 800 CFS. Originally intended as a signal for boaters, to alert them that the river is on its way down, new ecological concerns have been raised by CPW which must be addressed before this signal can be committed to. Furthermore, diurnal changes in flows are expected to exceed changes of 200 CFS during the recession, and it is likely the signal would be too difficult to distinguish to be useful, particularly further down the canyon.
- Please continue to check back on this site regularly for new updates. They are now expected to come primarily on Mondays and Wednesdays. Managers are currently planning to post when releases first drop to 800 CFS.
The following is more detailed information regarding how the spill will behave now that the reservoir has filled.
Earlier this year, releases from McPhee were managed to be as controlled and stable as possible, with standardized, measured changes following predictable ramping patterns. Because McPhee has reached full, releases will now follow reservoir inflows. Primarily, this means three things;
- First, that releases now follow a more natural hydrograph. Extended periods at set flows are unlikely. Instead, flows are behaving almost as if on an unmanaged river, reacting unpredictably to the combination of dynamic factors ranging from snow water content, coverage, and melt rates to solar radiation, temperature, precipitation, and transit loss. While reservoir operation moderates some of these rapid changes, releases will continue to 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 releases 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: