The Drying of the San Juan Watershed

Status
Not open for further replies.
JFRCalifornia

JFRCalifornia

Keeper of San Juan Secrets
A recent comment by @Trix got me thinking about flows on the San Juan, how they’ve changed over time, and whether or not the San Juan’s relative contribution to Lake Powell has changed in the past quarter century of drought. It the kind of thing that no one should ever be thinking about, but that’s the kind of nonsense that rolls through my head on a random Saturday. That, and the fact I need to mail a package at UPS.

In another post, I mentioned I was going to be rafting on the San Juan in a couple of weeks. Well, Trix pointed out the flow on the San Juan (at Bluff) was only 667 cfs that day, or 18% of the average for the date. I just looked today, and it’s now down to 608 cfs. Should I be concerned?

So I did a little digging. I first looked for the extremes on the San Juan. Not surprisingly, its most extreme flows happened before the construction of Navajo Dam in the 1960s. The dam has tended to smooth out the flows on the San Juan. The all-time flow on the San Juan happened on October 14, 1941, when it hit 42,500 cfs. (That’s the only day it ever exceeded 40,000 cfs.) In fact, 1941 was the biggest year recorded on the San Juan, when 4.89 maf passed Bluff on the river’s way downstream. That doesn’t sound like a lot compared to the contributions of the Green and Colorado, but for the San Juan, it’s huge. The average year on the San Juan since 1930 has been about 1.5 maf.

The highest flow ever recorded since Navajo Dam was in place? That would have been October 19, 1972. That day the San Juan flowed at 26,700 cfs.

So the simple fact that the San Juan has chronically low flows isn’t by itself a big deal in the big picture. It generally doesn’t produce much flow. In fact, before Navajo Dam, there were days when the San Juan was completely dry! For 10 days in July 1934, there was zero flow on the San Juan. Nothing. Dry. That happened again in August 1939. It hasn’t happened since, and that’s because of the dam. The worst yearly flow on the San Juan? That would have been 2018—0.44 maf. It was nearly that bad in both 2021 and 2022… in fact, several years since 2000.

And therein lies a theme. Historically, the San Juan’s contribution to Lake Powell (or before the lake, flow at Lees Ferry) was about 15% of the total, with the Colorado adding about 47%, and the Green about 38%. There’s a lot of annual (and seasonal) variation, but there’s your historic rule of thumb. But it does appear there’s a recent change in the trend we haven’t really seen before. The San Juan is contributing less than ever.

Here are the relative contributions of the three rivers in different time frames… plus the total regulated flows of those three rivers at the river gauge locations, which does not account for flows below Lees Ferry…

1930-63

Total Average annual regulated flows – 10.6 maf

Colorado – 47%
Green – 37%
San Juan – 16%

1964-2000

Total Average annual regulated flows – 11.0 maf

Colorado – 47%
Green – 38%
San Juan – 15%

Almost the same…

…but since 2000, here’s the breakdown:

Total Average annual regulated flows – 8.1 maf

Colorado – 48%
Green – 41%
San Juan – 11%

Put that in perspective. Not only are overall flows generally lower since 2000, the San Juan’s contribution to those flows is proportionally less…

What does that mean? It seems to indicate what we all see with our own eyes—there’s less runoff. But the fact that San Juan’s proportion is dropping really says something about that southern part of the watershed—it’s really dry and getting drier….

So the bottom line is this: will I have enough flow to raft the San Juan in May? Probably. Even in the worst years, flows tend to be stable or rise just a bit in May. Hopefully that means I won’t be dragging the raft much…
 
Last edited:
Until you put the flows in perspective of not only the changing temperatures but the losses due to pumping and evaporation this might be an exercise in futility anyways.

Are there any bans on new wells being drilled? Are there reductions in overuse of groundwater in place to bring groundwater in line with how much it is replenished each year? Are there any programs to even measure groundwater and to improve sustainable use of groundwater in the region?
 
In 1982 I was houseboating with friends on the San Juan River. My buddy in his 18 foot Avenger outboard went up the San Juan almost all the way to Mexican Hat. Residents were waving to him as he went upriver. He had to end his trip upriver due to boat gas concerns, but always said he wanted to do it again, and anchor at Mexican Hat and have a marguerita. As you might guess, that chance has never happened again.
In 1992 I went within 5 miles of the the San Juan Marina, which was no longer functional, but high winds turned me back. Since then, getting through Zahn Bay has been challenging. I haven't been back to the San Juan since 2021. I do really love the area.
 
This thread does bring back memories of the San Juan Marina........and it's questionable reputation leading to it's demise.... 🙄

If memory serves, wasn't there was a book out about the shenanigans going on there? :unsure:
 
Bill Sampson said:
In 1982 I was houseboating with friends on the San Juan River. My buddy in his 18 foot Avenger outboard went up the San Juan almost all the way to Mexican Hat. Residents were waving to him as he went upriver. He had to end his trip upriver due to boat gas concerns, but always said he wanted to do it again, and anchor at Mexican Hat and have a marguerita. As you might guess, that chance has never happened again.
In 1992 I went within 5 miles of the the San Juan Marina, which was no longer functional, but high winds turned me back. Since then, getting through Zahn Bay has been challenging. I haven't been back to the San Juan since 2021. I do really love the area.
Click to expand...
Two years ago we tried to get around the big bend to Zahn. Not happening in our outdrive, not least because the water was damn near plow able, and I wasn’t sure how much my impeller could take. A shallow draft jet would be fine, but probably pretty hard on your wear rings.
 
We love the SJ, but it’s been years since we ventured to Spencer’s Camp ,much less Zahn Bay

In the past few years we’ve found the bay between Piute and Neshki to be shallow, with green water and lots of whales. I’d love the opportunity to boat up to the old SJ marina again, but doubt that will ever happen
 
PowellBride said:
We love the SJ, but it’s been years since we ventured to Spencer’s Camp ,much less Zahn Bay

In the past few years we’ve found the bay between Piute and Neshki to be shallow, with green water and lots of whales. I’d love the opportunity to boat up to the old SJ marina again, but doubt that will ever happen
Click to expand...
I wonder if it would be possible during a low lake level to create a high flow event on the San juan and effectively dredge a channel to allow further upstream passage.
 
mobilerat said:
I wonder if it would be possible during a low lake level to create a high flow event on the San juan and effectively dredge a channel to allow further upstream passage.
Click to expand...
Seems like that would be logistically challenging to say the least. But even if you could, you would effectively be intensifying the rate of sedimentation further downstream and filling in more of the lower arm with silty goo…
 
JFRCalifornia said:
A recent comment by @Trix got me thinking about flows on the San Juan, how they’ve changed over time, and whether or not the San Juan’s relative contribution to Lake Powell has changed in the past quarter century of drought. It the kind of thing that no one should ever be thinking about, but that’s the kind of nonsense that rolls through my head on a random Saturday. That, and the fact I need to mail a package at UPS.

In another post, I mentioned I was going to be rafting on the San Juan in a couple of weeks. Well, Trix pointed out the flow on the San Juan (at Bluff) was only 667 cfs that day, or 18% of the average for the date. I just looked today, and it’s now down to 608 cfs. Should I be concerned?

So I did a little digging. I first looked for the extremes on the San Juan. Not surprisingly, its most extreme flows happened before the construction of Navajo Dam in the 1960s. The dam has tended to smooth out the flows on the San Juan. The all-time flow on the San Juan happened on October 14, 1941, when it hit 42,500 cfs. (That’s the only day it ever exceeded 40,000 cfs.) In fact, 1941 was the biggest year recorded on the San Juan, when 4.89 maf passed Bluff on the river’s way downstream. That doesn’t sound like a lot compared to the contributions of the Green and Colorado, but for the San Juan, it’s huge. The average year on the San Juan since 1930 has been about 1.5 maf.

The highest flow ever recorded since Navajo Dam was in place? That would have been October 19, 1972. That day the San Juan flowed at 26,700 cfs.

So the simple fact that the San Juan has chronically low flows isn’t by itself a big deal in the big picture. It generally doesn’t produce much flow. In fact, before Navajo Dam, there were days when the San Juan was completely dry! For 10 days in July 1934, there was zero flow on the San Juan. Nothing. Dry. That happened again in August 1939. It hasn’t happened since, and that’s because of the dam. The worst yearly flow on the San Juan? That would have been 2018—0.44 maf. It was nearly that bad in both 2021 and 2022… in fact, several years since 2000.

And therein lies a theme. Historically, the San Juan’s contribution to Lake Powell (or before the lake, flow at Lees Ferry) was about 15% of the total, with the Colorado adding about 47%, and the Green about 38%. There’s a lot of annual (and seasonal) variation, but there’s your historic rule of thumb. But it does appear there’s a recent change in the trend we haven’t really seen before. The San Juan is contributing less than ever.

Here are the relative contributions of the three rivers in different time frames… plus the total regulated flows of those three rivers at the river gauge locations, which does not account for flows below Lees Ferry…

1930-63

Total Average annual regulated flows – 10.6 maf

Colorado – 47%
Green – 37%
San Juan – 16%

1964-2000

Total Average annual regulated flows – 11.0 maf

Colorado – 47%
Green – 38%
San Juan – 15%

Almost the same…

…but since 2000, here’s the breakdown:

Total Average annual regulated flows – 8.1 maf

Colorado – 48%
Green – 41%
San Juan – 11%

Put that in perspective. Not only are overall flows generally lower since 2000, the San Juan’s contribution to those flows is proportionally less…

What does that mean? It seems to indicate what we all see with our own eyes—there’s less runoff. But the fact that San Juan’s proportion is dropping really says something about that southern part of the watershed—it’s really dry and getting drier….

So the bottom line is this: will I have enough flow to raft the San Juan in May? Probably. Even in the worst years, flows tend to be stable or rise just a bit in May. Hopefully that means I won’t be dragging the raft much…
Click to expand...
The San Juan -Chama water project was completed in 1976. I am not sure what year they actually started to divert San Juan water to the Rio Grand drainage. This may explain some of the drying of the San Juan system
 
Rainbowbridge said:
This thread does bring back memories of the San Juan Marina........and it's questionable reputation leading to it's demise.... 🙄

If memory serves, wasn't there was a book out about the shenanigans going on there? :unsure:
Click to expand...
I shared some pics on WW a few years ago of what remains of the Piute Farms Marina site. It was a trip I had wanted to do for several years. We saw the waterfall as well. I’ll see if I can post the thread link.
 
Raven Haven said:
I shared some pics on WW a few years ago of what remains of the Piute Farms Marina site. It was a trip I had wanted to do for several years. We saw the waterfall as well. I’ll see if I can post the thread link.
Click to expand...
Raven Haven

Thread 'San Juan Marina- We found it'

Next weekend will be our annual hiking and exploring trip based out of Bluff. This year, one of our planned day-trips is to head down SJC Road 423 to the site of the 1988-89 Paiute Farms Marina. I didn't start coming to Powell until '94 so I never saw the marina or anything past Zahn Bay. We will check out the waterfall while we're there as well. I'll take some pics of anything interesting and post them after Thanksgiving. There have been several posts regarding the marina over the years, but very little in terms of photographic evidence. Several years ago, a Wordling posted a cool...
  • Like
 
We camped and fished out of the old marina site several times. There were no buildings or evidence of the marina except the launch ramp which had been paved but the NPS made them remove that so it was a pretty steep gravel and broken pavement pieces on the surface. No trouble. The big problem with camping and fishing there was broken windows and lost equipment. Never happened to us but we camped well away for launch ramp and parking area. The parking area was cover with broken window glass and there were stories of stolen equipment and tires from vehicles and empty trailers. It was a long drive from the paved road just outside of Gouldings Trading Post to the marina site over a very rough, rocky road. 15-25 mph at most. Fishing was good, few people, very quiet. Chuck
 
“Will I have enough flow to raft the San Juan in May?”
That depends which section you’re doing. Bluff to Mexican Hat shouldn’t be a problem. More exposed rocks to worry about, but it should be runnable even at 600 - 700 cfs.
The problem comes if you plan to go down all the way to Clay Hills Crossing. I would not recommend taking a raft down that section if the flow is less than 1600 - 1800 cfs. The lower section, from Slickhorn Canyon down is heavily silted and you will probably end up having to drag your boats through stretches of shallow mud (which really sucks, I mean it will suck the shoes right off your feet).
I did that section in 2019 when it was flowing a little over 1600 and I still had to drag my Duckie through some shallow sections down on that lower part.
 
I've lived in Mexican Hat for almost 46 years! My family moved to Bluff in the 1940's...a lot of stories about the floods prior to Navajo Dam, the river would create up to 22' sand waves back then. I found this article that explains some of the diversions...rafting is always a hit or miss but we have a ton of rafters this time of year and the river is running!
Bureau of Reclamation
 
Status
Not open for further replies.
Back
Top