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Uvas Dam and Reservoir was constructed in 1957. Water from the reservoir is used to recharge aquifers beneath Santa Clara Valley. The spillway of Uvas Dam is one of the best exposures of "pillow basalts" in the region. Lumpy "pillows" of basalt in the stream bed appear relatively unchanged from when they formed on an undersea volcano long ago in the Jurassic Period (nearly 180 million years ago). Over time these rocks have migrated perhaps many thousands of miles across the Pacific Basin to where they may be seen today.
Uvas Reservoir fills the linear valley of Uvas Creek in the eastern foothills of the southern Santa Cruz Mountains. The land was once part of a Mexican land grant, Rancho Las Uvas (meaning "Ranch of the grapes.")
An elevated stream terrace consisting of sand and gravel of Quaternary age can be seen in the spillway area below Uvas Dam. The stream terrace deposits overlying pillow basalts exposed in the spillway channel.
