TABLE OF CONTENTS
Branches of the Eel River
Five major tributaries comprise the Eel River and its watershed.
The mainstem Eel is the largest sub-basin, stretching 200 miles from the Pacific Ocean to the headwaters above Lake (Reservoir) Pillsbury in Lake County. The river is fed by three mountains, each close to 7,000 feet’ÄîSnow Mountain, Rice Mountain and Hull Mountain’Äîin a bowl that gathers the water from a large number of tributaries and shoots it in a northerly direction. It is at this point that PG&E's Potter Valley Project diverts at least half the water from this headwaters basin to the Russian River to the south.
The Middle Fork is the largest tributary of the Eel with two main forks. The Middle Fork rises in the Yolla Bolly Mountains in Trinity County, while the Black Butte River flows from the north side of Hull Mountain in Mendocino County to join the Middle Fork just east of Covelo in Round Valley. The Middle Fork of the Eel then travels westward 70 miles through some of the most rugged wilderness in the state, draining 753 square miles, joining the mainstem at Dos Rios.
Further north near Highway 36 in the south end of the Hettenshaw Valley, contained entirely within Trinity County, the North Fork tributary drains 286 square miles and is 35 miles long.
The Van Duzen River tributary starts in the northern end of the Hettenshaw Valley and covers 420 square miles beginning in Trinity County and ending in Humboldt County, where it joins the mainstem of the Eel just south of Fortuna.
The South Fork begins in Mendocino County near Laytonville, traveling west a bit and then northeast before heading almost due north at Cummings, for a total of 105 miles, draining 689 square miles.
Until recently the Eel River has carried up to 5,846 tons of suspended silt per square mile, making it slightly siltier than the Yangtze River in China, somewhat less than the Nile River in Africa, and fifteen times greater than the Mississippi. This silt fills spawning beds, blocks sunlight necessary for microbes and plant life, and affects both the Eel and Russian rivers.
Part of the reason for so much sediment was the two devastating "thousand-year floods" that hit the Eel River basin in 1955 and 1964. So much soil and rock was washed from the freshly clear-cut hills that the river changed from a deep narrow channel to a wide gravel-choked riverbed. Ongoing logging as well as rural road systems contribute heavy silt to the rivers every year. However, during Pat Higgins' Chinook Monitoring studies of 2010 he noted that healing of the riverbed was apparent from reduced sediment in most of the river, as evidenced by bedrock and water clarity.