San Pedro River, AZ (June 21, 2025) — This summer, The Nature Conservancy in Arizona (TNC Arizona) and more than 80 volunteers and partner organizations came together to map approximately 270 miles of the San Pedro River and its tributaries, stretching from its headwaters in Mexico to its confluence with the Gila River. This year’s effort marked a major milestone in the transition to digital data collection, with nearly the entire watershed mapped using tablet-based tools. This is an upgrade from handheld GPS units that improves efficiency, accuracy, and data management. Full adoption of the new system is expected by 2026.

The 2025 mapping also expanded photo point monitoring, a method piloted in 2024, which tracks environmental changes over time by taking photographs from the exact location at regular intervals. The goal was to focus on three key areas: spring identification in collaboration with Sky Island Alliance, beaver activity to be shared with Watershed Management Group in Tucson, and log jam locations to help TNC and partners better understand how the river functions. Log jams—natural piles of fallen trees and debris that form in the river—can influence water flow, sediment movement, and the growth of new vegetation along the riverbanks.

The San Pedro River Wet/Dry Mapping project is a long-running citizen science initiative launched by TNC Arizona in 1999 to monitor the health of the river system. Each year on the third Saturday in June, volunteers, scientists, land managers, and staff- armed with hats, sturdy shoes, sunscreen and water – walk the river and its key tributaries to record the presence or absence of surface water. This provides an annual snapshot of the waterway’s condition at the end of the dry season.

TNC Arizona is currently analyzing the 2025 data and anticipates sharing results later this year. Once available, maps will be posted at azconservation.org, alongside results from previous years.

Mapping efforts are made possible by the dedication of our volunteers and the support of our partners, including Arizona Game & Fish Department, Community Watershed Alliance, Naturalia A.C., Pima County, Salt River Project, Sky Island Alliance, TNC Mexico, U.S. Army’s Fort Huachuca, U.S. Bureau of Land Management, U.S. National Park Service, and the many private landowners who granted access to their properties.

We are deeply grateful for the continued collaboration and commitment to protecting and understanding the San Pedro River watershed.