Lower San Pedro River Wildlife Area

The San Pedro River is the last major free-flowing, undammed river in the American Southwest. After flowing into Arizona from Mexico, the San Pedro River flows north through the Sonoran Desert for 140 miles until its confluence with the Gila River, a tributary to the Colorado River. The San Pedro River provides habitat for hundreds of species of birds and several threatened or endangered species.

The ecological significance of the San Pedro River cannot be overstated—in 1995, the American Bird Conservancy identified the river as a “globally important bird area” and “the largest and best example of riparian woodland remaining” in the Southwest. Groundwater pumping to support agriculture and expansive rural-development in the San Pedro Valley threatens the few remaining perennial stretches of the San Pedro River. Since 1940, groundwater pumping has decreased base flows in the river by 67%. Development along the San Pedro River continues undeterred—a proposed 28,000 home planned-community near the river in Benson is forecast to increase local groundwater pumping from 800 acre-feet per year to as much as 13,000 acre-feet per year.

The Lower San Pedro River Wildlife Area (LSPRWA) covers more than seven miles of the San Pedro River and includes nearly 600-acres of riparian woodlands. This collaborative project, which is a partnership between the Arizona Land and Water Trust (Trust) and the Arizona Game and Fish Department, converts over 100 acres of historic agricultural fields to a pasture of native grasses. The agricultural fields have traditionally been used to grow corn and wheat and were watered from two nearby wells located within a mile of the San Pedro River. By transitioning from high water-use crops to native grasses, the Trust estimates at least 710 acre-feet of water will be saved in the first six years of the phased crop conversion, with as much as 610 acre-feet per year thereafter.

* Project restores natural hydrologic conditions to facilitate improved capture and infiltration of surface water and groundwater recharge

** This resource has been reviewed and found to meet the BEF Flow Program Certification Criteria for Evaluating Proposals to Secure Environmental Flows by the National Fish and Wildlife Foundation.


Near Mammoth, AZ

Start Up Date:


Project Benefits:

Groundwater Replenishment

Wildlife & Habitat Improvement

Project Type:

Restoration of Natural Hydrology *


Fully Funded

WRCs Generated:

Yes **

Project Partners

Arizona Land and Water Trust, Arizona Game and Fish Department, Intel Corporation