Western Colorado Rain

ndscott50

ndscott50

Well-Known Member
Some areas of Southwest Colorado saw the highest rainfall totals in 50 years over the weekend. Well the flooding is unfortunate it does add some water to Powell and perhaps more importantly should send us into winter with a significantly improved soil moisture situation, which if we can get some decent snow this winter, will drive improved runoff in the spring. Here is the rainfall map month to date through Sunday, with more rain to come though Wednesday.
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Here is the Powell inflow forecast. We should see green numbers for the next 10 days or so.
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Note the current inflow around 17,000 is higher then all but 9 days of the spring runoff season - we peaked at 22,500 this year. This by no means solves the current water supply problem but it does lower the odds that we see a worst case scenario for 2026 inflow.
 
Yes, Those are single day totals. Three or four inches of rain in a day in that part of the country is pretty rare - particularly if you are not up on the highest slopes. As an example, the area around Vallecito Reservoir, around 8,000 feet, picked up over five inches over the weekend. That's probably a once every 50 to 100 year type of event. I have not really dug into the detail. I was relying on media reports indicating areas with the highest rainfall totals since 1974.

Edit to add some questions on overall rarity of this event: It would be interesting to see how rare this type of event is on a regional basis. Locally you can always have a complex of thunderstorm drop a ton of rain in one drainage and break records - that pretty common on a regional basis even if it only occurs in one specific location every 50 years. At lake Powell you might see this come into the lake as a 6 to 12 hour surge that adds several thousand CFS to the inflow. In this case its more widespread with the inflow into Powell jumping by 10,000 cfs and staying at that level for five days. Its also happening at a time of year where snow melt is not a factor. It would be interesting to look at the data and see how often that occurs.
 
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ndscott50 said:
Locally you can always have a complex of thunderstorm drop a ton of rain in one drainage and break records - that pretty common on a regional basis even if it only occurs in one specific location every 50 years. At lake Powell you might see this come into the lake as a 6 to 12 hour surge that adds several thousand CFS to the inflow. In this case its more widespread with the inflow into Powell jumping by 10,000 cfs and staying at that level for five days. Its also happening at a time of year where snow melt is not a factor. It would be interesting to look at the data and see how often that occurs.
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Not very often, as you might imagine. Probably the most sustained example of an October rise in recent memory happened in October 2006. From October 3 through November 1, inflows ranged from 12,000 to 34,000 cfs, and for two weeks stayed above 15,000 cfs, with five days above 23,000 cfs. In two days in early October, the lake rose 2.3 feet. In all, the lake added over 500,000 af to its volume in that month.

Both 1997 and 1998 had even longer sustained high inflows in October and November, but in each year outflows were high too, so the effect on the lake wasn't noticeable. Before that, you'd have to go back to the unprecedented run in the early 1980s, especially from 1982-86, when it seemed that high flows in the fall were just normal. The only other year at Lake Powell that really saw a dramatic jump in October was 1972, which had a few days where inflows topped 40,000 cfs in the wake of Hurricane Joanne, very much like the current set up with Raymond...
 
I noticed how the radar kept showing the storms training over eastern Utah and western Colorado. Seemed like day after day, it was most intense right in the same general area. Let’s hope the moisture keeps rolling through!
 
Tuesday - 14 Oct 2025 - 6:30am

The San Juan River through Pagosa Springs rose higher than the previous crest on Saturday. At 5 am this morning it hit 12.82 ft and 8,560 cfs.

Earlier today, floodwaters and debris caused a sewer line failure beneath the First Street Bridge on US Highway 160.

Highway 160 is closed in Pagosa Springs and on Wolf Creek

Archuleta County School District has closed schools in the district for today due to the high water and impact on infrastructure.

Mandatory evacuations will remain in place until ingress and egress has been evaluated and it is deemed safe to return to areas affected. The Evacuation Shelter is still open available to receive anyone that needs
 
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Great news for the whole watershed(minus the flood damage) , I don't think many take into account the amount of water downstream already which will allow them to trim back upstream significantly. All the way down to Yuma the fields are super flooded and irrigation needs for fall crops and winter plantings will diminished. The Salt River and Gila watersheds in Central AZ are SOAKED beyond normal and that's a good thing all the way up to Fontenelle. This should mean they can hold the upper lakes even longer before dumping in mid to late winter based on snowfall levels. Pray for even just an AVERAGE winter and things look good into spring runoff season.....OH and also pray they manage this water blessing properly.
 
Just watching LP gains this morning and the gains realized the last 5 days equate to 15days worth of releases....so that's pretty awesome we got 15days worth of releases in mid october and counting, plus Navajo went up multiple feet which equates to like 2 months worth of releases for them so we have lots of extra days banked so to speak already.
 
AndyMAC said:
Just watching LP gains this morning and the gains realized the last 5 days equate to 15days worth of releases....so that's pretty awesome we got 15days worth of releases in mid october and counting, plus Navajo went up multiple feet which equates to like 2 months worth of releases for them so we have lots of extra days banked so to speak already.
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Navajo is doing really well from all this rain. Looking at the CBRFC forecast it look like the reservoir will gain at least 125,000 acre feet of storage from this. Prior to the rain outflows were around 600 cfs while inflows were around 400 cfs. This led to a drop of around 800 acre feet a day. Inflows will likely stay well above the 600 cfs level through the end of the month (current forecast is to still be at 1520 ten days from now).

My guess is we won't see Navajo start to decline again until well into November and that that it will remain above its October 9 low for the rest of the water year. This storm essentially erased all of the decline we would expect to see through the winter. Only thing that would change this would be if they decided to up the releases.

Effects are less dramatic at Powell. Note the CBRFC does not provide a volume forecast so more guess work on that. Currently the lake is up 50,000 acre feet and forecast indicate it will continue to climb for around 10 more days. We will see at least another 10 days of more limited declines after that as inflows will be below the 8,000 cfs daily release but above the 6,000 cfs inflow we saw before the rain.

Overall lets guess the lake gains 125,000 acre feet. Prior to the rain it was losing about 4,500 acre feet per day. So this storm essentially erased a month of the decline we would expect to see through the winter. Helpful, but I still think the largest benefit is that we are now going into winter with wet soil which will greatly improve runoff in the spring if we can get some snow. Lets hope for some big November snow to get things rolling.
 
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