More than a year before Georgia's historic drought demanded the Atlanta area's attention, the U.S. Army Corps of Engineers accidentally released about 22 billion gallons of water downstream from Lake Lanier in 2006, while trying to save taxpayers $138.

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Pouya Dianat/AJC (ENLARGE)

A view of lone island near the Lake Lanier Islands as tourists will slowly start to pack the water ways with boats as the warm summer months approach.

Pouya Dianat/AJC (ENLARGE)

An aerial of Lake Lanier, which still appears water starved even after several heavy rains in the past few weeks.

David Tulis/AJC (ENLARGE)

A mix-up over a metal pulley cost Lake Lanier, pictured here last month, 22 billion gallons in 2006.

• Photos: Lanier revealed: A photographer's essay DEALING WITH THE DROUGHT: • The watering rules ... • ... And a few exceptions • 10 tips to save water • Map: Heavy demands on our water RELATED: Drought contributed to drowning deaths  Corps issues warning to July 4th visitors to Lake Lanier  Fourth of July boaters should beware of low lake levels  Talk of damming Flint River stirs anger  State: Drought will worsen so keep conserving  • More on coping with the drought

That's the cost of a simple metal pulley the Corps decided not to replace when workers thought they fixed a gauge that measures the water level at Lanier, the Atlanta area's main source of drinking water.

Because of a miscommunication over whether that part was replaced with a different-size pulley, the Corps calibrated the gauge incorrectly, according to a Corps investigative report obtained under the U.S. Freedom of Information Act. As a result, the gauge indicated the lake level was higher than it actually was, causing the Corps to release too much water downstream over a 52-day period ending in June 2006.

Though homeowners in the area squawked about the rapidly receding lake, Corps officials didn't notice because staff turnover left no one in the area familiar with the lake, said the brigadier general who made the report.

In the end, it was some unidentified, insistent residents who led to an immediate tightening of the spigot, an embarrassing news release from the Corps, the proper setting of the gauge, a tongue-lashing from Gov. Sonny Perdue, and the installation of redundant gauges at many Corps projects.

At the time, no one could predict the lake's nearly 2-foot drop would be part of a whopping 19-foot drop over the next months, capped with a near-total outdoor watering ban across the region and a record low for the lake.

However, that doesn't mean Lanier would have those 22 billion gallons today — or would have when a watering ban was declared last fall — state and federal water experts say. That's because the water was stored in lakes downstream and was used in conjunction with even more water released from Lanier. In short, the water would have been released eventually and would all be gone by now.

Still, the blunder raises questions about the stewards of our drinking water as we enter the third year of a drought that is not expected to end anytime soon.

The Corps releases water from Lanier for a variety of needs downstream, including power generation and to support two species of mussels protected by the Endangered Species Act. Under long-standing pressure from Georgia officials, the federal government lowered its required releases in November, and last week said it is considering lowering them even more on June 1.

The lake level is about 1,057.5 feet above sea level, or 13 feet below full.

The Corps' error is detailed in a 191-page investigative report. The Atlanta Journal-Constitution formally requested the report on Nov. 26 under the federal Freedom of Information Act. More than four months passed before the Corps provided a heavily redacted copy. The Corps eliminated from the report all the names of those officials responsible for the mistake, several pages of findings, and descriptions of exhibits.

Here is what the report says:

The mistake happened in December 2005 when Corps officials replaced a part on the lake-level gauge. When they did the work, they did not replace the pulley, part of the original equipment installed in 1961. The Corps called the equipment's manufacturer, Portland, Ore.-based Stevens Water Monitoring Systems Inc., and asked how to calibrate the equipment. A technician from the company recommended a setting based on the assumption that the pulley had been replaced with one of a different size in use today, the report surmised.

"The underlying reason for not replacing the pulley was an effort to be good stewards of taxpayer resources," said Brig. Gen. Bruce Berwick, commander of the Corps' Great Lakes and Ohio River Division, who was tapped by the Corps to lead the investigation. "Obviously, in retrospect, given the importance, it probably would have been a good thing to do."

Because the pulley didn't need to be replaced, the Corps could have saved $138 and still gotten the setting right if there not been a miscommunication with the manufacturer.

Stevens Water company officials declined to comment.

The Corps started investigating only after local residents complained that the lake level appeared too low, Berwick's report says. Asked why the Corps never noticed the lake level going down, Berwick blamed it on staff turnover.

"Because of recent turnover and loss of experience at that project, there wasn't anyone there who had a great familiarity with what the lake looked like at various levels," Berwick said.

Because the gauge indicated the lake level was higher than it actually was, the corps said it released an excess 420 million gallons of water a day over 52 days to boost water levels in the Chattahoochee River and the Apalachicola River.

The lake lost 1.9 feet of water over that time frame, falling more than five feet below full level. The lost water equals what the Atlanta metro area consumes from Lanier and the Chattahoochee in 118 days, according to the Georgia Environmental Protection Division.

In a June 17, 2006, news release, the Corps referred to the accident as a "gauge error" and "calibration error." Three days later, state officials, steamed by the mistake, filed a lawsuit against the Corps over how it manages Georgia's lakes, hoping to force the federal government to keep more water in Lanier.

"By this mistake, they essentially created a 'man made' drought on top of a natural drought," Gov. Perdue said of the gauge error during an Aug. 8, 2006, congressional hearing about the Corps' performance.

Since it discovered the mistake, the Corps has installed additional gauges at the lakes it manages in case others fail.

"The lesson was learned, I think, not just for Lake Lanier but for the Corps," said Brig. Gen. Joseph Schroedel, commander of the Corps' South Atlantic Division, which includes Lanier. "I can tell you, at least within the division here, we took the lessons learned from that and said, 'Whoa, let's go make sure that we have redundant... gauges at all of our systems.' "