The Nature Conservancy in Arizona - Walking & Mapping the San Pedro's Flows

Help protect a premier southwestern river: The San Pedro

The San Pedro River, one of the southwest's major undammed rivers, is a bird migration corridor of hemispheric importance.

Help the Conservancy conserve this magnificent waterway by contributing to "Nature Matters: The Campaign for a Sustainable Arizona."

Cool Green Science: Read the Conservancy's blog for more information on mapping the San Pedo.

The San Pedro River:
A Biological Treasure

Millions of birds use the San Pedro River corridor each year as they make their annual journeys between habitats in North, Central and South America.

The river supports an unusual diversity and density of mammals, amphibians, reptiles and insects.

The San Pedro, which flows north from Mexico, is a vital source of water for communities in Sonora and southern Arizona.

Notes From the Mappers...

"This was AWESOME - I would like to participate again next year."
— Beth Kruer, who along with her hiking partner, was "swooped" by a pair of Harris hawks defending their nest.

"This is the most water we've seen since we started mapping this section three years ago."
— Ted Mouras, who has previously seen Gila monsters, coatimundi, javelina and zone-tailed hawks on the stretch of river near the town of Tombstone.

Dale Turner and Amanda Amoros of the Conservancy saw a large black bear track while hiking the river through the San Pedro River Preserve.

More than 100 volunteers, conservationists and agency staff spent June 20, 2009 walking in groups that covered around 150 of the 170 miles of the San Pedro River, plus many of the river's key tributaries.

The goal? To map where the river is flowing and where it is not, and to provide insights into the health of this premier southwestern river system.

The mapping, done annually since 1998, is a massive collaborative effort that involves:

The Nature Conservancy
U.S. Bureau of Land Management
Community Watershed Alliance of Benson
Friends of the San Pedro River
citizen volunteers
Naturalia, a Mexican non-governmental organization
BIDA, a Mexican non-governmental organization
the Mexican park service - CONANP

"This is participatory science at its best. It connects people to this river in a real way," said Holly Richter, the Conservancy's Upper San Pedro River program director. "Many people do this year after year because they love this river."

River Mapping Provides Important Information

The Data: This year, 45 percent of the 150 river miles mapped had surface water flowing. Last year water was present in 39 percent of the 120 river miles mapped. (See last year's maps. This year's maps will soon be available.)

Mapping this river over time will provide insight into what might be the causes in fluctuation of flows — climate change, drought, groundwater or surface water withdrawals. The effort will also assess the habitat for beaver, fish and other aquatic organisms.

What's New: This year the mapping included several higher-elevation tributaries to the river as well as 30 miles in Mexico.

The Wildlife: Volunteers who walk or ride the river encounter a diverse array of wildlife species. This year's sitings included:

Raptors — gray hawks, a pair of nesting Harris hawks, turkey vultures
Songbirds — vermillion flycatcher, common ground doves, roughwing swallows, summer tanager, Bell's vireo
Other birds — great blue heron, Mexican mallards, great horned owls
Mammals — Beaver sign, bear tracks (at the San Pedro River Preserve near Dudleyville), deer
Reptiles — Mohave rattlesnake, frogs, toads. turtles
Fish — longfin dace (a native)

Nature picture credits (left to right): Photo © Tana Kappel/TNC (hikers on the San Pedro River); Photo © Holly Richter/TNC (GPS on horseback).