The Carson River watershed encompasses and includes two major forks in the Sierra Nevada in its upper watershed region. The East Fork rises on the north slopes of Sonora Peak (itself just north of Sonora Pass at about in southern Alpine County, southeast of Markleeville in the Carson-Iceberg Wilderness. The West Fork rises in the Sierras near Carson Pass and Lost Lakes at elevation and flows northeast into Nevada, joining the East Fork about southeast of Genoa. The Carson River then flows north to the end of the upper watershed at Mexican Dam just southeast of Carson City. In the middle watershed the river runs generally northeast from Carson City across Lyon County, past Dayton. The middle watershed ends in eastern Churchill County at the Lahontan Dam. Here river flows are augmented by water from the Truckee River and stored in the Lake Lahontan reservoir. Downstream from the dam (in the lower watershed) much of the water is used for irrigation in the vicinity of Fallon, with limited flows continuing northeast into the Carson Sink.