Mantua Bad Ice Spots

[dubob]

[font "Comic Sans MS"][#800000]Every year after ice-up on Mantua, the subject of areas of bad ice crop up in condition reports and fishing reports for Mantua. Lots of folks have seen them and a few have even been victimized by them. They do exist and folks need to use caution near them. I have no disagreement with any of this.

However, the source of these bad spots has intrigued me for several years and I did some research into the possible causes. The most commonly used cause is there are springs coming up from the floor of the reservoir. And this may be the cause. But verification of said springs doesn’t seem to exist.

I pulled up some pre-reservoir topo maps of the Mantua Valley dated 1955 and the only springs shown on those maps are the very same ones shown on today’s topo maps and they all exist right at the very edge of the reservoir or above its high-water line. There isn’t a single spring shown anywhere in the valley that now has reservoir water over it. I don’t have a clue as to what minimum size requirement the USGS needed to list a spring on its topo maps, but IF there were some springs in the valley, they were too small to be listed.

I found a thesis from a USU graduate student (Karen C. Rice) from 1987 on the Hydrogeology and Hydrochemistry of Springs in Mantua Valley and Vicinity, North-Central Utah that listed 11 springs feeding the reservoir and all were outside the boundaries of the reservoir proper.

Another possibility would be gas pockets in the valley; probably methane. But I couldn’t find any references that showed, or indicated the probability of, any gas pockets within the Mantua Valley.

So, the only thing we know for sure is that these bad ice spots exist. We don’t know for sure how many of them exist or their approximate locations – just that they are there somewhere. Nobody knows for sure what causes them as far as I can determine, but they are being caused by something. So be aware and be safe.[/#][/font]
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[TubeDude]

[#0000FF]I put up a post on this same subject several years ago, after someone posted a "map" of where the "warm springs" were on Mantua. Like yourself, I researched old maps...made prior to the creation of the lake...and could find no such springs.

However, I have observed the open pockets and weak spots that do appear from time to time in various locations. And they seem to be different each year. There does not seem to be the continuous "methane bubblers" in defined spots, such as there are in Bear Lake. But there does appear to be sporadic upward flows of either bubbles or warmer water from below the surface. I suspect that some of this may be due to decomposing water vegetation.

I have asked several folks from DWR if they have a good explanation and have gotten mostly the same suppositions as stated above.

But...bottom line...THERE AIN'T NO WARM SPRINGS IN THE BOTTOM OF MANTUA.
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[RockyRaab]

A bit fanciful, perhaps, but consider this: As the reservoir filled, the weight of the water depressed the land just enough to alter the underground flow of springs that formerly surfaced outside the bowl of the reservoir. And now, those springs are inside the high water line.
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[dubob]

[font "Comic Sans MS"][#800000]According to the thesis done by Ms Rice, the average depth of circulation for the springs in that area is over 100 m (328 ft) so I wouldn't think that is the cause. But I can't rule it out definitively. []
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