New Maps Provide Baseline for Flow of San Pedro River

San Pedro supports nearly half of the avian diversity in North America

SIERRA VISTA, AZ — April 9, 2008 — The first maps that track where the San Pedro River flows and where it is dry between Mexico to the Gila River are available today. These maps establish an important baseline for evaluating the San Pedro, the last major free-flowing river in Arizona and Sonora, Mexico, and a vital source of water for nearby communities. One hundred and twenty (120) river miles were mapped, out of the total 174 miles that the river flows.

The San Pedro supports nearly half of the avian diversity in North America. About 250 species — including 1 to 4 million migrating songbirds — use the riparian habitat annually as they move between wintering grounds in Mexico and Central America and breeding grounds in the United States and Canada. It also provides habitat for 80 species of mammals, including the elusive jaguar.

The new maps reveal that overall, 39 percent of the river remains “wet” — that is, it flows year round — a rarity for river systems in the arid Southwest. However, some areas of the river have lost year-round flowing water and now struggle to support a wide array of plants and animals.

San Pedro River © Harold E. Malde

According to Holly Richter, director of the Conservancy's Upper San Pedro Program, the river’s future requires additional efforts on both sides of the international border, and these new maps can play an important role guiding these efforts.

“The fate of this unique river will be increasingly dependent upon regional water management decisions made by many different entities within both the United States and Mexico in the coming decade,” said Richter. “This mapping project complements more traditional types of hydrologic data, greatly enhances our overall understanding of the river system and helps inform decisions regarding water management issues affecting the San Pedro River.”

Created by a partnership of The Nature Conservancy in Arizona, the U.S. Bureau of Land Management (BLM) and the Community Watershed Alliance, the maps show where water remained in the river in June 2007, the month each year when river flows are expected to be their lowest. While the Conservancy and BLM initiated monitoring on portions of the San Pedro in 1999, this is the first year the maps include the majority of the river, beginning in Mexico and ending where it meets the Gila River. The maps also include portions of the Babocomari River, one of the largest tributaries of the San Pedro.

These maps show that approximately 51 percent of the length of the river in Mexico had water, 52 percent of the river within the Upper Basin had water, and 21 percent of the river in the Lower Basin had water. Overall, water was present in 39 percent of the length of the river for the 120 miles mapped.

Many factors, including human water demand and climate, can influence how much water is present in the river each year. These maps enable annual comparisons and insights into areas of flow improvement or areas of concern.

“These maps provide a snapshot in time during critical summer base-flow conditions,” said Brian Bellew, the BLM's Tucson field manager. “We now can study the relationship between surface and groundwater, and the response throughout the San Pedro watershed to changing conditions. This helps us make the best land management decisions we can, so that we can fulfill our obligation to conserve, protect, and enhance the valuable resources of the San Pedro Riparian National Conservation Area.”

Dozens of volunteers including local citizens, landowners, academic researchers, ranchers, Salt River Project employees and the Community Watershed Alliance hiked or rode horseback along the river during a single day to collect data on where the river flows. Participants used global positioning system (GPS) units to identify the locations where water begins and ends over a total of 120 miles of the river. In the Benson area, the University of Arizona NEMO Program partially supported this work through a grant.

“This is a wonderful opportunity to build community partnerships while collecting factual information that can be used by us all,” said Mary McCool, executive director for the Community Watershed Alliance.

The maps are accessible at The Nature Conservancy’s Arizona science Web site www.azconservation.org and the Community Watershed Alliance Web site www.cwatershedalliance.com.

Additional Contacts
Lorraine Buck, Public Affairs Specialist
U.S. Bureau of Land Management
(520) 258-7240, lorraine_buck@blm.gov

Mary McCool, Executive Director
Community Watershed Alliance
(520) 609-2738, watergroup@aol.com

The Bureau of Land Management’s mission is to sustain the health, diversity and productivity of the public lands for the use and enjoyment of present and future generations. The Tucson Field Office manages the San Pedro Riparian National Conservation Area, part of BLM’s National Landscape Conservation System. Visit us online.

The Community Watershed Alliance is a community-based regional organization that promotes collaboration and cooperation to advance research, education, and policies for the sustainability of the Benson Subwatershed. CWA is comprised of landowners, residents, agencies, organizations, government, and interested parties committed to finding and supporting informed solutions. Visit us online.

The Nature Conservancy is a leading conservation organization working around the world to protect ecologically important lands and waters for nature and people. The Nature Conservancy’s Arizona chapter has been actively protecting nature and preserving life for nearly 40 years. Together with communities, private citizens, businesses and public agencies, it has helped to protect more than 1 million acres of significant habitat statewide. The Conservancy also owns and manages nature preserves in Arizona. Six preserves are open to the public for bird watching, hiking and nature studies. For more information on The Nature Conservancy in Arizona and how to visit its preserves, visit us on the Web at nature.org/arizona or call our Tucson conservation center at (520) 622-3861 or our Phoenix conservation center at (620) 712-0048.