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Sunday, November 07, 2004

The Curious Route Water Takes Underground

Ever in my quest to understand the therma-hydrodynamics of where the hot water comes from at Scenic I thought I'd park this interesting little factoid here in the hopes it would explain something at a later date.

Scenic has an unusual configuration for a hot springs. Normally, the water emerges hottest at the lower elevations but Scenic is the exact opposite. Supposition is that this is because the water flows are very shallow from the upwell source and on down the slope . . . thoughts that are borne out by the fractured substrate layer just beneath the soil layer.

Others have also commented that Scenic responds to ground water and snowmelt percolation on a faster than normal schedule from most hot springs . . . often a good rainfall affecting the temperature of the spring water within days.

Today, one of the long-term soakers, Dale, pointed out the pressure dynamics of freshly percolated water into the springs . . . and one that is fasinating.

At the main springs, there are two sources of hot water . . . probably primary upwells. One is reliably hotter than the other by several degrees (and this is the one that fed the 'infamous' Lobster Pot pool in days begone. However, today the two springs had reversed their temperature profiles. We all commented on that.


Facing east across slope at remaining 'Monster' tub. Treed area behind is a relatively flat area. You can see the two pipes that feed hot water from the primary spring sources.  The one in the back is the normally hotter springPosted by Hello

The explanation put forth goes likes this, and you have to imagine the geology. Looking into the slope (uphill) from the remaining pool is a disjoin of granite boulders from which the normally hotter of the two springs emerges. To the left of this disjoin is a large and relatively flat area slightly higher than the spring outlets, themselves. On the right is continuation of the steep slope from higher up the hillside. From here emerges the normally slightly cooler second source spring.

When it rains heavy or snow begins to melt on that flatter area to the left the water pools subsurface and as it is heated it begins to exert a sideways-to-the-right pressure on the granite disjoin where the hotter spring emerges . . . with the result that water flows go up and the temperature is tempered by the new water. The other spring now gets the hotter water coming up from lower down in the substrate.

Once the percolated water seeps through the flat area and is discharged at the spring, the pressure is lessened and the roles once again reverse to hottest on the left and slightly cooler on the right. Fasinating hypothesis.

Rick (aka banged-up-shins)

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