Upper San Leandro Reservoir is an artificial lake located in Alameda County and Contra Costa County, California. The reservoir is closed to boating and fishing to protect water quality, which means paddling is not permitted on this body of water.

The reservoir has a capacity of about 42,000 acre-feet, with a normal volume of approximately 30,250 acre-feet. It is impounded by the San Leandro Dam, an earth-filled structure 182 feet high and 1,300 feet long, situated at the southeast end of the lake.

While paddling is prohibited, visitors can enjoy the surrounding area through a public trail system. The King Canyon Loop Trail skirts along the northern edge of the reservoir, offering hikers views of the water body and surrounding landscape. The trail winds through forests of California bay trees and oak trees, providing opportunities to observe local flora and fauna.

Wildlife enthusiasts may spot various bird species around the reservoir, including waterfowl, wrens, finches, and raptors. The reservoir and its feeder streams are home to a population of landlocked rainbow trout, whose migration to San Francisco Bay was blocked by the dam's construction.

The reservoir was originally formed in 1926 and receives water from several tributaries, including San Leandro, Moraga, King Canyon, Kaiser, Buckhorn, and Redwood Creeks. Most of its water, however, is imported via the Mokelumne Aqueduct.

For those interested in the area's history, the reservoir's creation inundated a section of the San Leandro Creek valley, including the towns of Valle Vista and Redwood. The current dam, constructed in 1977, replaced an earlier structure to provide better protection against earthquakes.

While paddling is not an option at Upper San Leandro Reservoir, the surrounding trails and natural beauty offer alternative recreational opportunities for visitors.