The 65.0-mile-long (104.6 km) South Yuba River is a left-entering tributary of the Yuba River originating in the northern Sierra Nevada at Lake Angela in Nevada County about three quarters of a mile north of Donner Pass, about three miles east of the town of Soda Springs. After passing through Lake Van Norden with Upper Castle Creek (longer than the Lake Angela stem) entering from the right, it gathers numerous snow-fed tributaries running west through a marshy, lake-filled valley, criss-crossing Interstate 80. The river briefly enters Placer County, then flows into Lake Spaulding, then plunges westward into a steep-sided valley. Canyon Creek enters from the right, then Poorman Creek also from the right near the town of Washington. The river continues west into the foothills, crossing und