Thursday, July 28, 2016

Natural Bridges Monsoon Waterfalls

Monsoon thundershower waterfalls into White Canyon, near Sipapu Natural Bridge.
Visitors to the Colorado Plateau--especially to canyon country--are often surprised at our late summer "monsoon" thunderstorm season. When we usually get half of our annual precipitation. The other half being wintertime snow.

Rain coming down by the buckets! It won't last long.
Lately I got to watch another such event. In the late morning, cumulus clouds were building to the north over the mountains. They soon turned into towering thunderheads, the result of moisture from the south (Baja California) colliding with our hot dry summer blue skies.

A waterfall in two parts!
I drove Bridge View Drive to get a look down into White Canyon during the storm. On the east side of the park it was pouring so hard I didn't dare get out to photograph. Instead I lowered the passenger side window and shot right from the cab of the truck.

A heavy rain in the high desert starts running off fast. Especially when large portions of the watershed are bare sandstone slickrock. It's going to go downhill of course, and channeled into grooves and washes in the rock. To pour off of any cliff that's in the way.

Zooming in on one canyon rim waterfall, I was surprised to see that it had two parts to it. The surface tension of the rock made some of it run down the cliff face. But when the force of the water became too much, the rest was vaulted off into space from the very rim. I'd never seen--or at least noticed--that before.

Rain, rain, rain. Down the canyon walls of Cedar Mesa Sandstone.
I then drove the rest of the loop road through the park. Typical of desert thunderstorms, it was raining locally--very locally. The west side of the park, only about five miles away as the raven flies--was receiving almost no rain.

So I drove around the loop a second time (it's one way) to see what was going on in the rainy side of the park.

Notice the difference in turbidity (how muddy different flows are).

It had backed off some. Enough that I could get out and photograph instead of staying huddled in my vehicle and shooting through the downpouring curtain of water.

It was interesting to see how clear some of the waterfalls were, and how muddy others were. It all depends on what part of the site it's draining: bare rock, or soil.

Visitors taking in the temporary spectacle. Almost an inch of rain fell in about an hour.

 Photo location: Natural Bridges National Monument, southeast Utah.

© Copyright Stephen J. Krieg

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