Sonoran Institute has identified a realistic path to introduce water to one of the driest reaches of the Santa Cruz River—and it’s based on more than hope.
Through scientific research, hydrologic modeling, and sustained community engagement, we’ve developed a viable plan to introduce surface water into the Middle Santa Cruz River (MSCR). Stretching from the Santa Cruz–Pima County line to the southern edge of the Tohono O’odham Nation’s San Xavier District, this reach of the river has remained dry not because of neglect, but because of its geology. In this area, the solid rock layer underground (bedrock) is deep beneath the riverbed. This means the underlying soils along the river hold more groundwater and river flows tend to sink underground instead of flowing on the surface where we can see it.
Our solution? Use high-quality treated effluent—already a proven water source in other parts of the Santa Cruz—to restore flow in this arid section. This approach builds on successful restoration work in Tucson and elsewhere, adapting it to the MSCR’s unique conditions.
With support from the Bureau of Reclamation’s WaterSMART program and coordination through the Santa Cruz Watershed Collaborative, Sonoran Institute led a science-based planning process. We evaluated infrastructure, mapped hydrologic dynamics, and modeled restoration scenarios. Our findings show that the Green Valley Water Reclamation Facility (WRF) is ideally positioned to support restoration. Its effluent is clean, its infrastructure is in place, and its location avoids impacts to tribal lands.
The result is a set of conceptual designs for flow reintroduction. The most immediate—Concept 1—would use existing infrastructure and surplus
effluent to create 0.75 miles of surface flow, supporting native vegetation, wildlife, and public access. Pima County is already moving forward with permitting to bring this vision to life.
This project shows how federal investment can spark regional collaboration and lead to scientifically sound, community-supported outcomes. It also demonstrates Sonoran Institute’s capacity to lead interdisciplinary planning projects that blend ecology, engineering, and local knowledge.
Bringing flow back to the MSCR isn’t just a technical achievement—it’s a statement of what’s possible when partners work together for a common goal. With Concept 1 nearly shovel-ready and long-term options on the table, the Middle Santa Cruz River is poised for a revival.
And with it, a new chapter for a river that has long endured and is now ready to thrive.
Written by: Luke Cole, PhD | May 2025