Eel River (California)
The Eel River is a major river, about long, in northwestern California. The river and its tributaries form the third-largest watershed entirely in California, draining a rugged area of in five counties. The river flows generally northward through the Coast Ranges west of the Sacramento Valley, emptying into the Pacific Ocean about downstream from Fortuna and just south of Humboldt Bay. The river provides groundwater recharge, recreation, and industrial, agricultural and municipal water supply.
The Eel River system is among the most dynamic in California because of the region's unstable geology and the influence of major Pacific storms. The discharge is highly variable; average flows in January and February are over 100 times greater than in August and September. The river also carries the highest suspended sediment load of any river of its size in the United States, in part due to the frequent landslides in the region. The river basin also supports abundant forests – including some of the world's largest trees in Sequoia sempervirens groves–and, historically, one of California's major salmon and steelhead trout runs.
The river basin was lightly populated by Native Americans before, and for decades after, the European settlement of California. The region remained little traveled until 1849, when Josiah Gregg and his exploring party arrived in search of land for settlement. The river was named after they traded a frying pan to a group of Wiyot fishermen in exchange for a large number of Pacific lampreys, which the explorers mistook for eels. Explorers' reports of the fertile and heavily timbered region attracted settlers to Humboldt Bay and the Eel River Valley beginning in 1850. Starting in the late 19th century the Eel River supported a large salmon-canning industry which began to decline by the 1920s due to overfishing. The Eel River basin has also been a significant source of timber since the days of early settlement, and continues to support a major logging sector. The river valley was a major rail transport corridor for the Northwestern Pacific Railroad beginning in 1914 and continuing throughout the 20th century, and also forms part of the route of the Redwood Highway.
Since the early 20th century, the Eel River has been dammed in its headwaters by the Potter Valley Project to provide water, via interbasin transfer, to parts of Mendocino and Sonoma Counties. During the 1950s and 1960s, there was great interest in building much larger dams in the Eel River system, in order to provide water for the State Water Project. Although the damming would have relieved pressure on greater California's overburdened water systems, it stirred up decades of controversy, as some of the proposals made little economic sense and would have been detrimental to an ailing salmon run. The Eel was granted federal Wild and Scenic River status in 1981, formally making it off-limits to new dams. Logging, grazing, road-building, a burgeoning cannabis industry, and other human activities continue to significantly affect the watershed's ecology.
Course
The Eel River originates on the southern flank of Bald Mountain, in the Upper Lake Ranger District of the Mendocino National Forest in Mendocino County. The river flows south through a narrow canyon in Lake County before entering Lake Pillsbury, the reservoir created by Scott Dam. Below the dam the river flows west, re-entering Mendocino County. At the small Cape Horn Dam about east of Willits, water is diverted from the Eel River basin through a tunnel to the East Fork Russian River by the Potter Valley Project.Below the dam the river turns north, flowing through a long, isolated valley, receiving Outlet Creek from the west and then the Middle Fork Eel River from the east at Dos Rios. About downstream, the North Fork Eel River–draining one of the most rugged and remote portions of the watershed–joins from the east. Between the North and Middle Forks the Round Valley Indian Reservation lies east of the Eel River. After this confluence the Eel flows briefly through southwestern Trinity County, past Island Mountain, before entering Humboldt County near Alderpoint.
The river cuts in a northwesterly direction across Humboldt County, past a number of small mountain communities including Fort Seward, receiving a number of small tributaries including Beatty Creek. The South Fork Eel River joins from the west, near Humboldt Redwoods State Park and the town of Weott. Below the South Fork the Eel flows through a wider agricultural valley, past Scotia and Rio Dell, before receiving the Van Duzen River from the east. At Fortuna, the river turns west across the coastal plain and enters the Pacific via a large estuary in central Humboldt County, about south of Eureka.
The Northwestern Pacific Railroad tracks follow the Eel River from Outlet Creek, about above Dos Rios, to Fortuna. This section of the railroad has been out of service since 1998 due to flood and landslide damage. U.S. Route 101 runs along the South Fork Eel River and then the lower Eel River below the South Fork.
Discharge
Average flow of the Eel River varies widely due to its location, which places it more or less directly in the path of Pineapple Express-type winter storms. In the Mediterranean climate of its basin, almost all precipitation falls in the winter, and wet-season flows can be enormous, while the summer and early autumn provide only minimal precipitation, if any, causing the sometimes-mighty river to slow to a trickle. At its mouth, the Eel River produces an estimated annual runoff of per year, or about. The Eel's maximum recorded flow of on December 23, 1964, was the largest peak discharge of any California river in recorded history, and one of the largest peaks recorded in the world relative to the size of its drainage basin. In contrast, during the dry months of July through September, the river achieves nearly zero flow.The lowermost United States Geological Survey stream gauge on the Eel where flow volume is measured is at Scotia, where an annual mean of, or per year, was recorded between 1910 and 2012. This station measures runoff from an area of, or 85 percent of the basin; however it does not include the flow of the Van Duzen River, which joins several miles downstream. Monthly average flows at Scotia range from in January to in September – a 143:1 difference. The annual means also experience huge variations, with a high of, or, in 1983, and a low of, or, in 1977.
Reduction in flow occurs in part due to deliberate water diversion from the Eel to the Russian River watershed by the Pacific Gas and Electric Company's Potter Valley Project, located to the south in Mendocino County. Although the effect on the total annual flow is negligible the impact is much larger during the dry season, when the Eel's already-low natural flows are further reduced by diversions. Since 2004 the dams used by the project have been required to provide additional flow to the Eel River during the dry season, primarily to mitigate the negative impacts the project has on fish populations.
Eel River monthly mean discharge at Scotia
Colors=
id:lightgrey value:gray
id:darkgrey value:gray
id:sfondo value:rgb
id:barra value:rgb
ImageSize = width:800 height:280
PlotArea = left:60 bottom:30 top:30 right:60
DateFormat = x.y
Period = from:0 till:20000
TimeAxis = orientation:vertical
AlignBars = justify
ScaleMinor = gridcolor:lightgrey increment:1000 start:0
BackgroundColors = canvas:sfondo
BarData=
bar:Jan text:Jan.
bar:Fév text:Feb.
bar:Mar text:Mar.
bar:Avr text:Apr.
bar:Mai text:May
bar:Jun text:Jun.
bar:Jul text:Jul.
bar:Aoû text:Aug.
bar:Sep text:Sep.
bar:Oct text:Oct.
bar:Nov text:Nov.
bar:Déc text:Dec.
PlotData=
color:barra width:30 align:left
bar:Jan from:0 till: 19720
bar:Fév from:0 till: 19510
bar:Mar from:0 till: 14630
bar:Avr from:0 till: 9102
bar:Mai from:0 till: 3847
bar:Jun from:0 till: 1321
bar:Jul from:0 till: 350
bar:Aoû from:0 till: 151
bar:Sep from:0 till: 138
bar:Oct from:0 till: 643
bar:Nov from:0 till: 4708
bar:Déc from:0 till: 14230
PlotData=
bar:Jan at: 19720 fontsize:S text: 19,720 shift:
bar:Fév at: 19510 fontsize:S text: 19,510 shift:
bar:Mar at: 14630 fontsize:S text: 14,630 shift:
bar:Avr at: 9102 fontsize:S text: 9,102 shift:
bar:Mai at: 3847 fontsize:S text: 3,847 shift:
bar:Jun at: 1321 fontsize:S text: 1,321 shift:
bar:Jul at: 350 fontsize:S text: 350 shift:
bar:Aoû at: 151 fontsize:S text: 151 shift:
bar:Sep at: 138 fontsize:S text: 138 shift:
bar:Oct at: 643 fontsize:S text: 643 shift:
bar:Nov at: 4708 fontsize:S text: 4,708 shift:
bar:Déc at: 14230 fontsize:S text: 14,230 shift:
Watershed
The Eel River drains an area of, the third-largest watershed entirely in California, after those of the San Joaquin River and the Salinas River. The Colorado, Sacramento, and Klamath River systems are larger, but their drainage areas extend into neighboring states as well. The Eel River system extends into five California counties: Glenn, Humboldt, Lake, Mendocino, and Trinity. The main stem traverses four counties, excepting Glenn. The majority of the watershed is located within Mendocino and Humboldt Counties.The Eel's major tributaries–the North Fork, Middle Fork, South Fork and Van Duzen Rivers, drain,,, and, respectively. The Middle Fork drains the greatest area of all the tributaries, but the South Fork is longer, and carries the most water because of the higher rainfall in its basin.
The Eel River watershed is located entirely in the California Coast Ranges. The topography creates a general drainage pattern that runs from southeast to northwest, except in the Middle Fork basin and the Eel headwaters, where water flows from east to west. The watershed is bordered on the north by the basin of the Mad River, on the east by that of the Sacramento River, on the west by that of the Mattole River, and on the south by those of the Russian River and Ten Mile River. Major centers of population on the river include Willits, Garberville, Redway, Scotia, Rio Dell, Fortuna, and Ferndale. Minor communities include Laytonville, Branscomb, Cummings, Leggett, Piercey, Benbow, Phillipsville, Myers Flat, Shively, and Pepperwood. The river's relatively large estuary and delta, which includes the Salt River tributary and related creeks, is located just one low ridge south from Humboldt Bay and south of Eureka, the main city in the region.
Since the mid-19th century, logging activity in the watershed has loosened soil and destabilized aquifers, reducing the river's base flow, although the watershed is slowly recovering. Logging, grazing and other resource exploitation activities and their accompanying environmental changes have also increased the intensity of flood and drought. Prior to 2011, the Eel River basin consisted of 65.1% forest, 12.2% shrubland, and 19.2% grassland, with just 1.9% agricultural and 0.2% developed urban. The human population of the watershed is about 32,000–less than 10 people per square mile.
In the 20th century, much of the watershed area was included under state parks and national forest, including Six Rivers National Forest, Yolla Bolly-Middle Eel Wilderness, and Humboldt Redwoods State Park. A total of of the Eel River and its major tributaries are protected under the National Wild and Scenic Rivers system, with classed as wild, as scenic, and as recreational. About of the main stem are designated, from the mouth to a point just below Cape Horn Dam. The Middle Fork is also wild and scenic from its confluence with the Eel to the boundary of the Yolla Bolly–Middle Eel Wilderness. The South Fork is designated from its mouth to the Section Four Creek confluence, the North Fork from its mouth to Old Gilman Ranch, and the Van Duzen River from its mouth to Dinsmore Bridge.