The first shipment for the 2005 barge season went through the lock and dam at Rock Island Tuesday. Park Ranger Don Bardole with the U.S. Army Corps of Engineers has spent years explaining operations to visitors at lock-and-dam number fifteen. The boat that went through was named the “Cooperative Venture,” and is one of the big ones, the “line boats” that push a line of barges a thousand feet long and 105 feet wide, using about five-thousand horsepower. They’re called towboats, though they push the barges up the inland waterway. And the barges, all linked together, with the boat that pushes them, are called a “tow.” “It’s a water elevator,” he says, “that will take the tow from the lower level below the dam to the level above the dam,” compensating for the natural drop in the river’s elevation. Water tends to flow downhill, and he explains it doesn’t matter if that’s slowly or quickly, or whether the differential’s a few feet along miles of river, or 45 feet, and sometimes “there’ll be over a 100-foot drop at a lock.” Rock Island was the first lock-and-dam built on the upper Mississippi around 1933, and uses no pumps, just the natural current, to raise the water level in the lock so a string of barges can navigate the steep stretch of river. Every place there is a lock, there’s a dam, he explains, because the system creates a system of slow-moving lakes on the river, deep enough for the towboats to operate. A lock is not big enough for a standard tow any more, and the typical string of barges must be taken apart into two pieces to pass through. Once navigation season gets underway in earnest next week, he says it’ll take all day to pass 8 or nine complete tows through it on their way up and down the river. To view the system online through the Rock Island “River Cam,” surf to