Every summer, more than 200,000 people visit Lake Travis to boat, swim and get some sun. But longtime Austin resident Robert Baumgardner is more interested in the geography of the lake than recreation. Specifically, he's interested in the Sometimes Islands.
These islands are landmasses in the lake, right off Mansfield Dam. When the water level is low, you can see them. When it’s higher, you wouldn’t know they exist.
Because the islands’ visibility depends on the lake’s changing levels, local TV news stations often refer to them in weather reports. After seeing this, Baumgardner, a former researcher in UT Austin’s geology department, began to question their name.
“I just see it on the weather forecast when they're talking about the lake level, as if that were the official name of those episodically exposed islands,” Baumgardner says. “And I don't think that's the fact.”
So he asked about the origins of the Sometimes Islands for our ATXPlained project.
Baumgardner said he thinks the islands’ inconspicuous name comes from a navigation chart. He said maybe someone noted that the islands aren’t visible at all times and wrote “Sometimes Islands” in shorthand as a navigation hazard for boaters.
“I don't think they're called the Sometimes Islands, but it's a poetic name,” Baumgardner says. “I like it.”
Because of their location off of Mansfield Dam, the Sometimes Islands lie under the Lower Colorado River Authority’s jurisdiction.
Although little information remains in the record about the landmass name’s origins, LCRA communications specialist Patrick Badgley sticks to the common explanation.
"What gives it its name is the fact that when Lake Travis is high ... the geologic formation isn't clearly visible," he says, "but when it's low, you can see it. So hence the 'sometimes you see it, sometimes you don't.'"
The Austin History Center’s managing archivist, Mike Miller, could find only one map in the center’s collection that included the Sometimes Islands in its topography.
“You don't see this Sometimes Island because they drew the map when the assumption was the lake was full,” says Miller, whose specialty lies in cartography.
He says the Sometimes Islands appear because of the uneven topography of the land underneath the water, which was formerly called Horseshoe Bend.
"It looks exactly like a horseshoe, with the dam on one foot of the shoe, basically," he says. "And the land that's in the middle of that horseshoe, of course, is much higher than the river valley, the river bed underneath it."
Miller guesses the creation of the name was sometime in the 1950s and '60s, when the county was hit by a major drought. He says the earliest reference to the Sometimes Islands at the History Center was in a newspaper clipping from the 1970s. The name probably arose during a major drought in the late 1950s, when they would have first become visible, he says.
“Those are probably the first times after the formation of the lake that the water levels dropped to a point where the islands would appear,” Miller says.
Though he follows with the common explanation for the island’s name, Miller says mistakes easily end up in maps and are hard to fix.
“Once it starts getting repeated, everyone starts using it, it's used a lot – even though maybe the origin was incorrect,” Miller says. “But no one went back to that first iteration of that name to verify, and because it gets repeated, it sticks.”
If you want to check out the islands for yourself, and maybe even give them your own personal name, you’re out of luck. Even though Austin has had a brutally hot and dry summer, the spring was pretty wet and for now, the lake levels are just too high.