All across Texas, the bones of history lie in watery graves. From the ribs of sunken ships to the grave sites of prehistoric Texans, uncounted treasures abound beneath the surface of rivers and lakes. For state archeologists, these sites are untapped treasures - hard to reach but relatively protected.

Now, though, with the state in the grip of devastating drought, such sites are emerging from receding waters and - for the first time in years, experts worry - becoming vulnerable to looters and vandals.

Since mid-summer, the Texas Historical Commission, which oversees such locations, has, on average, learned of a newly exposed site each month, said Pat Mercado-Allinger, the agency's archeology director.

Among the sites are four cemeteries, including an apparent slave burial ground in northeast Texas' Navarro County. In central Texas, fishermen recovered a human skull thought to be thousands of years old.

An unspecified number of additional sites have emerged from waters overseen by the Lower Colorado River Authority. An agency spokeswoman refused to discuss details, saying that even divulging the number of newly exposed sites could induce the unscrupulous to search out and pilfer them.

Sunken history

East Texas waterways shroud dozens of sunken vessels, from early Texas ferries to steamboats and World War I-era cargo ships. While most of these craft probably remain underwater, state nautical archeologist Amy Borgens said, their appearance above water could occur at any time.

Such sites, most of which were submerged before Texans became appreciative of archeological treasures, can be vital in helping researchers fill the gaps of state history, Mercado-Allinger said.

"In many ways, this is the only way we can learn about these times and the people who came before us," she said. "I would hope that people who might encounter any archeological sites … would consider the damage they might do."

Mercado-Allinger urged those making such discoveries, which are protected under the Texas Antiquities Code, to contact the historical commission's Austin office. Looting or vandalizing such sites can bring penalties of up to 30 days in jail and a $1,000 fine per offense.

Thus far, the historical commission has received no definitive reports of sites being looted or damaged.

Under normal circumstances, such sites would be safely submerged. However, with most of the state in the throes of what the U.S. Drought Monitor calls an "exceptional" drought - the worst category in its five-level rating system - that situation is likely to change.

Water levels of East Texas rivers are well below normal; earlier this year, the Neches was at its lowest point in 90 years.

Borgens said as many as 300 shipwrecks litter Texas rivers and river mouths. Only 13 have been investigated. While many of the vessels likely were stripped of machinery and artifacts before they sank, a few could provide tantalizing clues to an era when commerce moved by water.

"Many of these are significant because their construction was unique or they were built regionally," she said.

They also can shed light on now-vanished communities they served.

Blessing and curse

"You know, it's kind of both an opportunity and a misfortune," Mercado-Allinger said of receding lake and river levels. "It does give us an opportunity to view these resources, but we don't have the (financial) resources to deal with them. The historical commission is working with other partners out there to help accomplish these tasks."

At a very basic level, she said, her agency is trying to facilitate exhumations from submerged graveyards, with reburial of occupants in perpetual care cemeteries.

"It all depends on how much is exposed, where it's exposed and what's happening to it," she said. "It may be that one option is just to let the water to cover them again."

allan.turner@chron.com