The concrete walls jutting out above the south bank of Putah Creek may seem out of place among the foliage of the Arboretum. But in fact, the moss-covered structures have stood for much longer than some of the surrounding trees. The walls are all that remain of Briggs Reservoir, the oldest known reservoir in California's Central Valley. Pioneer George Gregg Briggs built the reservoir, along with 200 miles of distributing pipe, to irrigate his acres of orchards and vineyards during the 1870s. Briggs pumped water from his reservoirs using gasoline engines until the turn of the century. Modern farmers destroyed most of the irrigation pipes and reservoirs during the following decades, but the establishment of the arboretum in 1936 protected Briggs Reservoir. Look for the landmark just east of the Putah Creek Lodge. — By Mike Sintetos

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