Esopus Creek is a 65.4-mile-long (105.3 km) tributary of the Hudson River that drains the east-central Catskill Mountains of the U.S. state of New York. From its source at Winnisook Lake on the slopes of Slide Mountain, the Catskills' highest peak, it flows across Ulster County to the Hudson at Saugerties. Many tributaries extend its watershed into neighboring Greene County and a small portion of Delaware County. Midway along its length, it is impounded at Olive Bridge to create Ashokan Reservoir, the first of several built in the Catskills as part of New York City's water supply system. Its own flow is supplemented 13 miles (21 km) above the reservoir by the Shandaken Tunnel, which carries water from the city's Schoharie Reservoir into the creek.