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Rainwater Catchment System

Rainwater catchment at Alcatrax

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.

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 Garden Conservancy Project Manager Shelagh Fritz talk about the island’s rainwater catchment system.

Rainwater catchment system

rainwater cisterns


On the west side of the island and beneath the bathing facilities, provision was made to let the bath water settle and draw it off to be used on the lawn and shrubs.”

Fred Reichel, secretary to Warden Johnston, 193441