Clouds of mocha-colored silt surround an island of driftwood and other debris where the Colorado River meets the eastern edge of Lake Mead. As the drought-stricken lake shrinks, the confluence has moved as much as 25 miles downstream. Photos by Ruben Luevano. Jim Holland, park planner for Lake Mead National Recreation Area, surveys low water conditions Wednesday at South Cove, the lake's eastern-most boat ramp.

LAKE MEAD NATIONAL RECREATION AREA -- Near the jagged mouth of Iceberg Canyon, a floating island of driftwood spins slowly in an eddy where rusty brown water meets blue.

Lake Mead didn't used to end here. As little as 10 years ago, the clear waters of North America's largest man-made reservoir stretched east another 14 miles by boat, right to the edge of Grand Canyon National Park.

Since then, the muddy line that marks the confluence of the Colorado River and Lake Mead has crept in the general direction of Las Vegas at an uneven clip.

"As the lake continues to drop, that confluence will continue to move downstream," said Jim Holland, park planner for Lake Mead National Recreation Area.

It is a side effect of the drought that comparatively few people see, since more than 70 miles of open water still separate the lake's quiet eastern edge from the bustle of Hemenway Harbor, just down the hill from Boulder City.

But for Trent Keller and other Colorado River guides, the change has been impossible to miss.

"It's been dramatic because Lake Mead has dropped so much," said Keller, who has rafted through the Grand Canyon and into Lake Mead 136 times since 1984. "The whole Pearce Bay used to look like any of the other bays on the lake. Now it has sandbars 10 or 15 feet above your head."

The confluence itself is marked by a stark line where the mocha-colored river sheds its silt as it meets the still water of the lake. Fueled by the river's current, eddies form to trap muddy branches and other floating debris in an area roughly the size of a baseball infield. It is thick enough for grackles to land on and poke around for something to eat.

"That's driftwood and plant material that have moved down the river from the Grand Canyon," Holland said during a recent boat trip to the lake's eastern edge.

A few, scattered pieces of human trash -- an empty egg carton and what looks like part of a pink flotation device -- color the temporary island.

In the distance, a Park Service sign warns boaters about shifting sandbars and other hazards upstream. Holland said the sign needs to be moved. It used to be in the right place, but the confluence has passed it by.

Park rangers patrol the area upstream of the lake in jet boats designed to operate in shallow water.

Outboard motors are not advised beyond the confluence, but even with a jet drive, boaters need to follow the river's current or risk colliding with a sandbar, Holland said. "It's not a place for an inexperienced boater to venture into."

For Holland, who grew up in Boulder City, this is the lowest he has seen Lake Mead since the 1960s, when much of the river's flow was trapped behind the new Glen Canyon Dam to fill Lake Powell for the first time.

Keller, who serves as operations manager for Western River Expeditions, said the overall experience of rafting through the Grand Canyon is largely unchanged by the drought, though the low water "makes things more difficult from a river-running standpoint."

For one thing, the trip has gotten longer.

Before the drought left it high and dry, the boat ramp at Pearce Ferry, Ariz., was the main take-out point for river rafters. Now many raft trips end at South Cove, 16 miles downstream.

If the lake continues to shrink, the take-out could be forced to move again. The next closest boat ramp is at Temple Bar, another 15 miles by boat.

Holland said the Park Service would do everything it could to maintain lake access at South Cove, including the construction of a new launch ramp not far from the existing one.

Ultimately, though, it could prove to be a losing battle.

Since 1998, Lake Mead has dropped 86 feet and lost about 200 miles of shoreline.

The water level is projected to drop another 13 feet by this time next year, and almost 20 feet by summer 2008, when the lake is expected to hit its lowest mark in 41 years.