MARTINS MILL, Texas » For more than three years, the lake on Jack Mewbourn’s ranch here held a secret at its murky bottom: A 1999 Chevrolet Monte Carlo. His grandson was the first one to notice the top of the car peeking out of the water. It wasn’t luck, or even fate. It was drought.

The water level in the 7-acre lake has dropped about 5 feet from a lack of rain. Stand on the grass lining the lake’s edge today, and in any other year you would be standing nearly waist-deep in water.

On a recent Saturday, Mewbourn, a longtime rancher in this rural unincorporated community about 90 minutes southeast of Dallas, took a boat to the middle of the lake with two of his grandsons. They confirmed that the small object they thought at first might be a barrel was indeed a car. Mewbourn called a local constable, and with the help of a diver and a tow truck, the vehicle was slowly dragged out. Inside, still buckled into the driver’s seat, were the remains of Brenda Kay Oliver, who had been missing since July 2008.

Oliver’s relatives said she had never recovered from the trauma of her 19-year-old son’s suicide. He had drowned himself in a nearby lake. The authorities believe Oliver, 55, took her own life by driving her car into Mewbourn’s lake, about a mile from where her sister, the last person to see her alive, had been living at the time.

Mewbourn and the Van Zandt County constable, Pat Jordan, have found themselves in recent days calling a cruel thing like a drought a strange sort of blessing.

"If it wouldn’t have been for the drought," Jordan said, "she’d probably still be in the car in that lake."

The historic drought that has devastated crops and forced millions of Texans in small towns and large cities to abide by water restrictions has had at least one benefit: As lake levels have dropped around the state, objects of all kinds that had been submerged for years, decades and even centuries are being revealed. Some of the discovered items are common debris like computer monitors, tires and sunken boats. But much of it has attracted the attention of historians, anthropologists, criminal investigators and, in one case, the National Aeronautics and Space Administration.

Long-submerged marble tombstones from the 1880s have become visible in the receding waters of Lake Buchanan in central Texas. Near the Texas-Louisiana border, the grave sites from an early 19th-century cemetery have turned up at one drought-stricken lake. Pat Mercado-Allinger, the director of the Texas Historical Commission’s archaeology division, said one water authority estimated having roughly 200 previously unreported archaeological sites resulting from lowered lake levels.

"The drought in Texas has been so severe and so widespread, across essentially the entire state, that we’re hearing reports from all over," said Mercado-Allinger, who was reluctant to discuss precise locations of many sites because of concerns for looting. "There are artifact collectors out there and looters who look for opportunities and go add to their personal collections or mine the sites. We have to be very careful."

At Lake Georgetown north of Austin, where the water level has dropped 23 feet, fishermen found a human skull at the edge of the water last month. The Georgetown police initially thought it might be related to the 2002 disappearance of a 19-year-old woman, but the skull was ultimately found to be of historical, not criminal, significance. It is believed to be the skull of a Native American man that is hundreds or thousands of years old, and is being studied in a lab by anthropologists at Texas State University in San Marcos.

In East Texas at Lake Nacogdoches, which has dropped 12 feet in the drought, residents stumbled onto a much larger object in late July. It was a spherical aluminum tank, 4 feet in diameter, that was cracked on top and sat in the mud at the lake’s edge. NASA officials later determined that it was a piece of debris from the space shuttle Columbia, which disintegrated during re-entry in 2003, killing the seven astronauts aboard.

The debris, one of 18 cryogenic tanks used to store the oxygen and hydrogen that provided electrical power to the shuttle, was put on a truck and driven to the Kennedy Space Center in Florida. Only one of the 18 tanks remains missing, a NASA spokeswoman said.

At Richland-Chambers Reservoir in north-central Texas, which has decreased more than 8 feet, a post-Civil-War-era cemetery of freed slaves has emerged along the shoreline. The wooden coffins and the remains of more than 20 African-Americans, most of them children, have been found. A skull was first discovered in 2009 after the lake level dropped, but when the waters rose again, the site was submerged, forcing local amateur historians to wait.

"Everybody hates the drought, but I needed the drought," said Bruce F. McManus, chairman of the Navarro County Historical Commission. "I knew it was there."

Despite periodic rainstorms, lower temperatures and even snowfall in Amarillo late last month, Texas remains in the midst of one of its worst droughts.

From January through October, statewide rainfall totaled 10.77 inches, about 15 inches below average. The 12-month period from October 2010 through September 2011 was the driest 12-month span in Texas since at least 1895, when statewide weather records began, breaking the previous record low set in 1956 by 2.5 inches.

"It’s the most severe single-year drought on record," said John Nielsen-Gammon, the state climatologist and a professor of atmospheric sciences at Texas A&M University. "There literally is no point of comparison."

Nielsen-Gammon said that the drought would persist and that most of the state would be experiencing major drought through next summer.

"We have so much rainfall to make up, it’s unlikely to be made up in the spring and summer," he said.

The water levels at many of the state’s man-made lakes have become a drought barometer. Lake levels have decreased statewide by as little as a few feet to as much as 50 feet or more. Some lakes are completely dry, and others are close to it. Lake E.V. Spence in West Texas, which normally has a maximum depth of 108 feet, is less than 1 percent full.

In Canton in East Texas, the drought has hurt Donna McWilliams as it has other Texans — she and her husband lost trees and sold off cattle because of a lack of hay — but it also helped her. She is the sister of Oliver, whose body was found in Martins Mill.

Oliver’s relatives had mailed fliers with her picture to homeless shelters and clinics, and put them up in local restaurants and pharmacies, always hoping, always wondering.

"I guess ‘closure’ is the word," said McWilliams, 60, one of Oliver’s two sisters. "Now we don’t have to wonder anymore. I do think the drought is a negative, but if there’s anything that can happen good out of a drought, it’s this, and it’s a blessing."