The Park Service calls the environmental impact statement (EIS) a successful attempt to balance its mission of resource preservation in the canyon, while also enhancing recreational opportunities on the river. Critics call the document a sellout to outfitters who guide thousands of visitors downstream annually.

The EIS, initially released last year and finalized following a public comment period, completes a process that dates back to 2002. Its core mission: to regulate visitor use in ways that are consistent with natural and cultural resource protection. The plan also attempts to balance river use between commercial and noncommercial users, determine levels of motorized and nonmotorized boat use and define appropriate levels of helicopter use.

"We believe our process has been open-minded, transparent and fair," Grand Canyon National Park Superintendent Joseph Alston said in a statement. "We have spent the last several years listening to and responding to a wide range of comments from individuals, groups and organizations."

But the plan for managing the 277 miles of river through the park has been panned by environmental groups, which accuse the Park Service of bending to commercial interests, even in the face of a recent U.S. Geological Survey study that documents the decline of native fish species, as well as the erosion of the river's beaches due to flows out of Glen Canyon Dam upstream from the park.

"This plan should focus on protecting the wild character of the Grand Canyon, and it should emphasize resource protection for future generations. Unfortunately, it does neither," said Roxanne George, Grand Canyon program coordinator for the Sierra Club.

"The USGS report is a clear indication that the Colorado River is suffering. The Park Service's plan to actually increase recreational impacts is not only unsustainable, it's inexcusable," she added.

Under the Park Service's preferred alternative for the segment of river between Lees Ferry and Diamond Creek, motorized and nonmotorized craft will be allowed on the river for 5 1/2 months out of the year (April 1-Sept. 15), with 6 1/2 months of nonmotorized use (Sept. 15-March 31).

The plan also calls for smaller group sizes and fewer daily boat launches during peak-use months, but also allows for what the Park Service calls a "moderate" increase in yearly visitors from the current 22,500 to 24,657.

Under the preferred alternative for the segment between Diamond Creek and Lake Mead, the Park Service has put use limits and a redistribution of Hualapai River Runner operations, which translates into lower levels of pontoon boat use than the Hualapai Tribe proposed. Peak daily use for commercial day trips will mirror current use, but the number of overnight trips could increase from the current three launches per month to three per day.

Noncommercial river users will continue to apply for permits through a lottery, which is held annually.

But critics say a system that already was weighted too heavily toward commercial outfitters is even more tilted toward them now.

jbaird@sltrib.com