Picacho Reservoir, reservoir in Pinal County, Arizona, US

Picacho Reservoir lies 11 miles (18 km) south of Coolidge in central Arizona. Built in the 1920s, it was designed to hold 24,500 acre-feet (30,200,000 m3) across more than 2 square miles (5.2 km2). Siltation and vegetation have since reduced its capacity, so much of it is now a shallow marsh with extensive stands of cattails and rushes.

Picacho Reservoir was built in the 1920s as part of the San Carlos Irrigation Project, storing and regulating water for the Florence-Casa Grande and Casa Grande Canals. Its design capacity was 24,500 acre-feet with a surface of over 2 square miles. Siltation and vegetation have since shrunk both, leaving much of it a shallow marsh of cattails and rushes.

The reservoir reflects the region's long dependence on water management and irrigation, with its name tied to the Picacho area's early farming heritage. Visitors today experience how the landscape adapts to seasonal changes, with fishing and bird-watching becoming part of the local rhythm of outdoor recreation.

The reservoir is easily accessible by car from Coolidge and requires no special equipment to visit, though there are no major facilities like cafes or restrooms on site. Bring your own supplies and check water conditions before visiting, as the lake can be completely dry during drought periods.

The reservoir can disappear entirely during drought years, transforming from a body of water into dry grassland, making it a dynamic landscape that changes dramatically from season to season. This cycling between wet and dry states creates shifting habitats for fish, frogs, and migratory birds.