Anglers also flock to the Arkansas. Colorado's parks department gave a 100-mile (160-kilometer) stretch in the headwaters park a "gold medal" rating because of the number and size of its fish.
"It is one of the state's outstanding brown trout fisheries," said David Nickum, executive director of Colorado Trout Unlimited. It's the longest section of gold medal river in the state, Nickum said.
The drought is constricting many other rivers in the south-central and southwestern U.S., including southern Colorado.
"It all boils down to how the weather patterns move across the state," said Tony Anderson, a National Weather Service hydrologist in Pueblo.
"It's remarkable how often there is a boundary condition between southern and central Colorado, how one side of the line gets water and the other side doesn't," he said.
The northern boundary of the drought is an undulating line that wanders east from Salt Lake City, dips into central Colorado and then runs across northern Kansas.
One Colorado river on the dry side of the boundary, the Rio Grande, is in far worse shape than the Arkansas.
"It's fairly bleak," said Gus Goodbody, a hydrologist with the National Water and Climate Center, part of the U.S. Agriculture Department. "Extremely low flows is what we're looking at this year, on par with 2002, which was a record low."
And conditions on the Arkansas River worsen once it leaves Colorado and flows into Kansas, Oklahoma and the state of Arkansas. The river depends more on rain and groundwater there, and the drought is shrinking those sources, the U.S. Geological Survey said.
In Colorado, the Arkansas benefits from an injection of water from the Fryingpan River on the other side of the Sawatch Range. A system of reservoirs and tunnels called the Fryingpan-Arkansas Project siphons water eastward from the Fryingpan to the Arkansas.
The Fryingpan got its name from a story about a wounded trapper who took shelter along the river. A companion hung a frying pan in a tree to guide him to the spot when he returned with help, according to the Geological Survey, whose job includes overseeing place names as well as monitoring stream flows and other duties.
The Arkansas will get a slightly above-average amount of water from the Fryingpan this year, according to Roy Vaughan of the U.S. Bureau of Reclamation, which manages the Fryingpan-Arkansas Project.
The imported water is released on a schedule that benefits both rafters and anglers by keeping the Arkansas headwaters at the right level at the right time under a voluntary agreement among state, federal and water district officials.
But it primarily benefits downstream users in Colorado, including about 60 drinking water systems and more than 310 square miles (810 square kilometers) of farmland, said Chris Woodka, a spokesman for the Southeastern Colorado Water Conservancy District, which owns the rights to the Fryingpan-Arkansas Project water.
The Fryingpan-Arkansas is one of nine major Colorado projects that move water across the Continental Divide, from the west side of the state to the east, according to the Colorado Water Conservation Board, the state's primary water agency.
Those projects have always been contentious, especially if the water — like the Fryingpan — would otherwise flow into the heavily used Colorado River. But users in eastern Colorado are legally entitled to it under the state's water rights system.
Thousands of farms and millions of people on the east side of the Colorado mountains would not have enough water without the diversions. Denver, the state's largest city, gets about half its supply from the Colorado River.