Breach Watch

Oops, the die may have already been cast for the Dolores. Capacity is 6,924 ft. May 1 elevation is reportedly 6,910.87.

If my quick math is close, three or four days of 4000 cfs inflow (as predicted) exceeds capacity (unless offset with damn releases). Looking at the DWCD website, inflow rate of about 1000cfs seems to raise McPhee elevation by about 1ft, even with max flow to the canals, etc. I'll leave the detailed math and odds of an uncontrolled spill or breach for others to calculate/confirm.

I recall a post on one of the threads saying releases should have started in early to mid April to extend the boating releases. This bit of wisdom is consistent with the pre-damned era hydrograph, and would have benefitted all involved, except of course, the hold-out water hoarders at DWCD and the Wrecked Bureau who control the gates, and perhaps, the damn's fates.

They're reacting at the moment.


It's not like CRBFC hasn't been putting out that the amount if water expected is higher than historical maximums - they have been.
I take DWCDs spill duration estimates with a very large grain of salt. They're so conservative in these estimates that it seems like they're surprised when melt happens and as if they aren't aware of remotely sensed snow data for middle elevations. Snowpack is enormous this year and at snotels there's basically an entire above average melt yet to happen.

There's enough water in the mountains that they could maintain a 3000 CFS spill for 50 days and that's including ag demands and refill that will inevitably occur. Would have been nice for the river outlet to hit some base flows early before filling and capitalize on the awesome low elevation runoff that's kept it going for the last month as well as save some headboard.

With regards to a breach, its a non zero chance bit still incredibly low. Worst case they open ag works and flood fields to capitalize on the ~1000 cfs available from outlets and also draw down narraguinnep for another few hundred cfs. This at the same time they max out the river outlet at 5000. Given the peak flow forecast daily median of around 4600 you could plausibly get away with that. Max peak flow forecast still doesn't exceed outlet capacity assuming you open every spigot to accommodate canal capacity. Still, a different philosophy than fill then spill would benefit all user groups.

My last wonder is if the river outlet works could emulate a diurnal hydrograph. Not sure how fast it can go up and down but would be really nice to mimic flows on the upper stretch which would extend the recreational season and benefit hydrology and habitat. If someone can make the may 4 meeting please ask for me I'll be out of town.

The DWCD website data has not been updated since May 3, as of May 9. Something to hide? Too busy cutting plywood?
Plenty of current data available elsewhere. Here's a good aggregation: https://mcphee.water-data.com/

Last prediction for Dolores inflow is 50% probability 5900cfs peak this year. Conditions haven't changed that much since the prediction. High country rain and warm nights predicted for the next seven days above the damned reservoir. Things might get VERY big and VERY real in the next couple weeks if current conditions converge. Gotta go somewhere. Water and gravity don't care about DWCD's entitlement complex.

Droboat said:

With no actual math to support, maybe the chances are about 50% of deploying emergency operations with a decent chance they fail.

Click to expand...

There's 22,323 AF capacity remaining or 5.44 feet until full. There remains 308,677 AF yet to run off from this years snow pack based on CRBFC's median forecast, of which ~89% will be released for recreational purposes once accounting for average diversions in this timeframe. This amount equates to another 46 days at 3,400 CFS which is the current release. The release will have to increase in response to peak flows from the Dolores which have yet to occur. While you are correct of the median peak of ~5,900 in town, with spillways at full bore that's net 900 CFS. 900 CFS per day into McPhee is equivalent to 1,785 AF/day. By maintaining ~6 feet of headboard space the operators have effectively accounted for peak average (not instantaneous) flows of 7,000 CFS for six days (net 2000 CFS). While the peak may certainly be high, it is outside of any forecast or historical occurrence. Sure, maybe it's a 1 in 1,000 event, who knows. That's .01% - incredibly low.

Now there is a wet pattern coming up that will result in a rain on snow event. High country of the Dolores is expected to receive up to 1.75" of precipitation in this event, with only the highest elevations receiving snow. Even with this moisture factored in CRBFC increases their median runoff forecast only by about 12k AF. If this all ran off at once on top of ongoing runoff it would be about an extra 2,000 CFS/day for a week or so - with the big unknown being how much additional runoff the rain would trigger. This may will trigger the peak flows, and the peak may well be up near max predictions, but keep in mind the max observed peak on the Dolores was in 1922 at 6950 CFS. So while it may well be capable of breaking a record peak flow, it appears the DWCD has accounted for this contingency and will be able to handle that scenario for up to six days, five once you include increases in flow from Lost Canyon Creek.



50% is an incredibly high estimate. To achieve an unmanaged release, flows upstream would have to average at least 8,000 CFS for at least four days in order to overtake the 5,000 CFS outlet works capacity combined with ~1,000 CFS agricultural diversion capacity (remembering the 2,000 CFS/day buffer that exists in the reservoir). I would imagine DWCD would ramp diversions up to maximum and intentionally flood ag lands rather than risk the alternative. Let's keep in mind what we're actually talking about here - the consequences of a dam failure would be catastrophic for all user groups, boaters included. McPhee dam is 270 feet above streambed and holds back 381,000 AF at full pool. If water overtopped the dam and began to work down, these uncontrolled releases would result in devastation of the Dolores River Canyon as well as all points downstream. If this occurred and the flow was 30,000 CFS, the height of that water at Bedrock would be 45'. For reference it is currently at 12.15'. This figure goes up exponentially. Nothing in the lower Dolores would ever be the same again and it would also devastate the local communities who rely on this water, whatever your opinion on that matter is.




So when I say the odds are incredibly low, I think we're dealing with a 1,000 year flood event, so .01%. Given the consequences of even this very low probability, I think it behooves everyone to be aware of how important it is to maintain space in the reservoir to account for the unknowns and remember what it is we're actually discussing, which is a complete disaster for southwest Colorado if it were to occur.

As the gates open to dump 4000 cubic feet per second out of McPhee, the plot thickens. Is this the year the water gods get together with the river gods and say enough is enough?

.HYDROLOGY...
Issued at 230 AM MDT Sat May 13 2023

Storm activity creeping into the forecast may change conditions
rapidly. Please stay up to date on current conditions and river
forecast if recreating on, or near the Western Slope`s main, snow-
fed tributaries. Weather forecast guidance has maintained an
anomalously moist plume streaming into the Four Corners by this evening,
bringing convective showers and thunderstorms. Warm, moist air
(whether raining or not) could accelerate snowmelt across mid to
high snowpack basins. As a result, several hydrographs are
forecast to climb back above bankfull and potentially spill over
flood stage next week. Timing of said peaks fluctuate per
drainage, and there`s certainly a higher level of uncertainty due
to the complexity of rising temperatures AND adding in the
potential for convective rainfall. However, southern ranges may be
more susceptible to rising water earlier on in the forecast due
to the proximity of the moist airmass anticipated this weekend.

Meanwhile, Water Hoarders may be starting to find out some things.


McPhee Release Update for Friday May 12, 2023
Posted By Eric Sprague On May 12, 2023
Notice: Starting at 09:30 AM today, releases from McPhee began ramping up from 3,400 CFS to 4,000 CFS, which releases should reach by 4:00 PM today. Flows should remain at 4,000 CFS until Tuesday, May 16th when we’ll provide further updates.
This increase in releases is intended to create more storage in the reservoir in anticipation of a possible spike in runoff over the next few days resulting from rainfall onto the snowpack. Rainfall can accelerate the snowmelt unpredictably, and the active weather pattern over the upper Dolores basin through the next week has a strong likelihood of rain at higher elevations where the majority of the snowpack remains.
We will continue to monitor conditions and will update this page as the spill progresses.

Looks like NOAA has maps and lists for such things in the Colorado River Basin.

Storms and warm nights just spiked the Dolores River above McPhee. Sun and afternoon storms in the high country forecast every day for more than a week.

Each March, The Water Hoarders "told you to reject the evidence of your eyes and ears. It was their final, most essential command.”

― (with apologies to) George Orwell, 1984

Droboat said:

Storms and warm nights just spiked the Dolores River above McPhee. Sun and afternoon storms in the high country forecast every day for more than a week.

Click to expand...

There’s more slack in the reservoir now than the last time I replied to you. 6.56’ or 26,269 AF. McPhee is dropping 0.26 ft on average last 3 days. Remember, there is a difference between instantaneous and daily average flows. Todays instantaneous 5216 cfs is the 7th highest recorded peak, yet 24 hr average is just 4880 - which as I’ve stated is more than able to be handled given freeboard. Todays net flow is 1064 CFS or just over 2,000 acre feet. Sorry to burst your bubble, things are in better shape now than last week. The melt is certainly not done and this peak is quite early so I wouldn’t be surprised to see higher, which is awesome but not overly worrisome to the dam, excepting impacts to low lying areas above the dam which you don’t seem very worried about but are much more likely.

Go get on the river, we all know it won’t be like this again for a while.

Since we’re throwing out quotes, I like this one from Bertrand Russell; “The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.”

Well the Rio had a bit of a spike last night...
That's a lot of water. Interestingly at Rico it's only around 1,000 CFS so a whole lot is coming in between the gauges along the west fork and tributaries. I'm curious if it's a gauge error given the 750 drop and correction before the nearly instant 1400 spike followed by a normal curve, especially given cloud cover and light precip yesterday. If real this is the third highest peak the river has recorded, above the max peak flow forecast (most recent, april one had this flow at about 25%) but the hydrograph looks suspect. Guess I'll have to run into town and check!