The Upper Truckee River begins to coalesce at the southern edge of the Lake Tahoe Basin, just below Red Lake Peak, around 10,000 feet above sea level. The serpentine little river never really carves much of a canyon and flows 12 miles as the crow flies down to Lake Tahoe at 6,220 ft. Of the sixty three streams that flow into the lake, the Upper Truckee drains the largest sub watershed in the Tahoe Basin and is also the most disturbed by human activity.
Before 1959 and the construction of the Lake Tahoe Airport and the Tahoe Keys development, the Upper Truckee followed a mostly natural course, and just as the river bed nears the lake, water flowed into the largest marsh barrier system in the Sierra Nevada range at the southern shore of Lake Tahoe, the Upper Truckee Marsh.