Seaman Jeremy Brassard pushes a buoy over the side of the Coast Guard Cutter Kickapoo Monday while re-marking Mississippi River channel at the Vicksburg bend. (The Vicksburg Post/PAT SHANNAHAN)

Low water on the Mississippi River that’s still dropping has the U.S. Coast Guard in Vicksburg busy marking the river’s navigable channel.

The Cutter Kickapoo left the harbor at Vicksburg Monday on a four-day trip along 117 miles of the river to reset the red and green buoys that guide river traffic through deeper water.

The Kickapoo, a 130-foot boat with its barge, works the river between Natchez and Lake Providence.

High temperatures and unusual river fluctuations this summer have made the 13-member crew’s work especially difficult and especially important.

Monday, the river dropped 0.2 feet to 6.8 feet on the gauge at Vicksburg. While those numbers don’t measure depth, they do cause alarm.

“We could be in pretty bad shape in a month or two if we don’t get some rain up north,” Master Chief Petty Officer Tracy Johnson said.

In 1988, river stages got as low as minus 2 feet and forced closings on the river near Greenville. Last summer, river stages in Vicksburg dropped to a zero reading.

Maintaining the channel is the job of the U.S. Army Corps of Engineers. Survey boats constantly work taking measurements, and dredges can be put to work where needed. The Corps’ goal is a minimum channel 9 feet deep and 300 feet wide.

Johnson, in charge of the Kickapoo, has spent 30 years in the Coast Guard and the last four in Vicksburg. Buoy tending is normally performed every other week.

The buoys are 7 feet tall, made of steel and filled with plastic foam. Cable is used to attach them to 1,500-pound concrete weights.

The buoys, which are often run over by passing ships, cost about $450 each. They are placed, moved and replaced largely by hand.

Veteran river captains can often “see” safe water merely by looking at the patterns the current forms on the surface, but at night and especially in the case of unexpected shoals, steering between buoys can keep the massive arrays of 40 or more barges from grounding.

As water levels have dropped, the Coast Guard has moved the buoys to keep vessels in the deepest part of the river. The channel in the bend just upstream from the river bridges has been reduced to 621 feet. With some tows as wide as 222 feet, going downriver into the curve does not leave much room for error, Johnson said.

“This is the worst place we have on the river,” he said.

Piers on the bridge show the scars of many boats that have drifted out of the channel over the years.

The Coast Guard has asked the boating industry to reduce the width of its barges on the river and to reduce the load weight until water levels return to normal. So far, there have been no problems, Johnson said.

Two months ago, the USS Black Hawk moored in Vicksburg for five days as part of the Navy’s Mississippi River Cruise to St. Louis. River levels during the week the ship was here dropped to 15 feet.

Today, the Osprey-class coastal minehunter probably would not have made it past Greenville, Johnson said.

“He’d probably have a very nervous captain even getting to Vicksburg right now,” he said.

The dropping water level on the river had been a concern, as the craft displaces 12 1/2 feet of water. The ship’s engines were used to pull its docking barge away from the bank every day of its stay in order to move the ship further into the deeper water of the channel.