Is Lake Mead's Ominous Bathtub Ring Disappearing?

Water is slowly inching up the thick bathtub ring of calcium carbonate that bleaches Lake Mead's rocks.

After years of drought, Lake Mead, which is located in Nevada and Arizona, reached drastically low levels last summer, but the water levels have started to recover after a wet winter. Water continued to rise as snowpacks melted throughout the summer.

A white "bathtub ring" has bleached a thick band of rocks at Lake Mead for years and shows the severity of the decades-long drought that depleted the lake. As the water levels continue to rise this summer and submerge the rocks, the bathtub ring is slowly shrinking.

As of Monday, Lake Mead water levels were at nearly 1,060 feet, a steep 20-foot increase from this time last year, when levels barely cleared 1,040 feet. The lake still has a long way to go before it fully recovers, but rising water levels are erasing some evidence of drought.

Colin Williams, a mineral resources program coordinator with the United States Geological Survey (USGS) told Newsweek that the bathtub ring around Lake Mead is caused by calcium carbonate, which exists in the water that flows down the Colorado River. The minerals then adhere to the rocks around the lake as water laps against them. It is the same discoloration that causes a hard white scale on home faucets and stains the inside of a teapot.

When the lake's water level recedes during drought, the calcium carbonate remains on the rocks and creates the bathtub ring. As water levels rise again, the calcium carbonate doesn't disappear since it still exists in the water. Rather, the levels are submerging the minerals so they are no longer visible.

"Lake Mead is full at 1,229 feet above sea level, so the bathtub ring disappears when the lake level is near that point," Williams said.

Despite its ongoing recovery, Lake Mead still has nearly 170 feet to rise before its bathtub ring is no longer visible.

Lake Mead's chance at a full recovery is slim. Jennifer Pitt, the director of the National Audubon Society's Colorado River Program, previously told Newsweek that feat is only possible if three years of average snowfall occur with no water use from the reservoir.

The Colorado River feeds both Lake Mead and Lake Powell, so calcium carbonate stains the rocks at Lake Powell, as well.

A photographer pointed out the minerals at Lake Powell in a photo shared on Twitter last Wednesday.

"The red rocks that surround Lake Powell," the photographer said. "The white coloration caused mostly by calcium carbonate is disappearing as the water levels rise again."

At Lake Powell, a full pool is at 3,700 feet above sea level. Current levels are at 3,583 feet, meaning that the bathtub ring at Lake Powell won't be covered until the lake is much closer to full capacity, according to Williams.

Despite the partial recovery at both lakes, water levels have started to taper off as summer progresses because of high temperatures and low precipitation. The levels are expected to decline before the next wet season starts in the fall.