Other than fog drip and winter rains, Alcatraz Island is without a source of fresh water. Historically, both the military and the federal prison had built cisterns to capture rainwater, but these fell into disrepair after the prison closed. Because the National Park Service is dependent on water brought by barge to the island, the Gardens of Alcatraz project team installed a rainwater catchment system in 2009. By using the historic concrete cisterns that recycled water from the former federal prison showers, the system can capture 12,000 gallons of rainwater, meeting the garden's annual water needs.

Alcatraz Historic Gardens rainwater catchment system cisterns

Alcatraz Historic Gardens rainwater cistern tanks

WaterSprout Landscape Design and Construction created the gravity-based water-catchment system. Water from the cellhouse roof drains to the downspout and is directed to the historic cisterns. The water passes through a large filter that catches feathers and larger debris, and a first-flush diverter prevents the water with smaller particles from being collected. Next, the water is sent through a sand filter where beneficial bacteria neutralize any harmful bacteria. After filtering, the rainwater flows to four new storage tanks.

Watch Senior Project Manager Shelagh Fritz talk about the island’s rainwater catchment system.