Stony Creek is a -long tributary of the Sacramento River in Northern California. It drains a watershed of more than on the west side of the Sacramento Valley in Glenn, Colusa, Lake and Tehama Counties.
Originating on the eastern slope of the Coast Ranges, Stony Creek flows north through an extensive series of foothill valleys before turning east across the Sacramento Valley to its confluence with the Sacramento River, about west-southwest of Chico. Stony Creek is the second largest tributary to the west side of the Sacramento River; only Cottonwood Creek is larger. Stony Creek is an important source of water for agriculture in the Orland area. The creek has native rainbow trout and historically had significant ocean-going runs of steelhead.
Stony Creek was named for the large amount of rocks and sediments it once washed down from the mountains during floods. Today, most of the sediment is trapped behind Black Butte Dam, a flood-control structure built in 1963. It is labeled on some maps as "Stoney Creek" or "Stone Creek" and was historically known as the Capay River.
Course Stony Creek begins as North, Middle and South Forks in the Mendocino National Forest west of Stonyford. The North Fork, long, originates near the border of Lake and Glenn Counties, almost immediately flowing east into Glenn County, before turning south toward the Colusa County line. The Middle Fork begins near the summit of Snow Mountain, which at is the highest point in both Colusa and Lake Counties, in the Snow Mountain Wilderness. It flows west, north then east through Lake and Glenn Counties in a large semi-circle for , before joining with the South Fork in Colusa County. The South Fork flows in a northeast direction entirely within Colusa County, joining the Middle Fork less than a quarter-mile (0.4 km) upstream of the North Fork. The main stem of Stony Creek begins at the confluence of the North and Middle Forks.
The main stem of Stony Creek flows east into Indian Valley, turning north at Stonyford and re-entering Glenn County, before receiving Little Stony Creek from the right. It continues in a generally northward direction for about through various parallel north-south ridges and sedimentary valleys of the Coast Range foothills. At Elk Creek it is dammed at Stony Gorge Dam to form Stony Gorge Reservoir. Below the dam it receives Briscoe and Elk Creeks from the left, and is crossed then paralleled for several miles by California State Route 162. It receives its largest tributary, Grindstone Creek, from the left at Grindstone Indian Rancheria. Stony Creek then turns sharply northeast, flowing through a wide valley towards Black Butte Lake.
Black Butte Lake, formed by Black Butte Dam in Tehama County, is the largest reservoir on Stony Creek, covering more than in the lower Coast Range foothills. A second tributary called North Fork Stony Creek joins in the reservoir from the west. Downstream of Black Butte Dam surface water from Stony Creek is diverted into the Stony Creek Canal and other smaller ditches for irrigation. The creek re-enters Glenn County, flowing in an east-southeast direction across the Sacramento Valley as a wide meandering stream. North of Orland, the largest town in the watershed, it is crossed by Interstate 5. It joins the Sacramento River south of Hamilton City and west of Chico at Sacramento river mile 190 (kilometer 306).
The average unimpaired runoff of Stony Creek was for the period 1921 to 2003, with a maximum of in 1983 and a minimum of in 1977. Runoff peaks in the winter and early spring, with a low summer baseflow of less than . Historically, flood flows of could be expected once every 50 years. Dams now control the winter flow in lower Stony Creek to no more than , and the creek bed is often dry in the summer due to water diversions.
Watershed
The Stony Creek watershed consists of mostly in the Coast Range foothills and a smaller area of the Sacramento Valley. The area experiences a Mediterranean climate, with cool, wet winters and hot, dry summers. The annual precipitation, 90 percent of which falls between November and April, ranges from on the valley floor to in the headwaters. The watershed above Black Butte Dam drains about , or 95 percent of the whole. Grindstone Creek drains the largest area of any tributary, at , followed by Little Stony Creek at .
Black Butte Dam is considered the boundary between the upper and lower Stony Creek watersheds. Above Black Butte Dam, most of the watershed is publicly owned in the Mendocino National Forest and various BLM and state lands, while about 96 percent of the lower watershed is privately owned. Lower Stony Creek has formed an extensive alluvial fan in the Sacramento Valley which slopes downhill to the east. The alluvial fan extends about north to south and east to west, and is made up mostly of fertile, well-drained soils. Beneath the surface is the Stony Creek aquifer, whose primary source of recharge is Stony Creek. The aquifer has an estimated volume of and is an important water source for agriculture.
Water quality in upper Stony Creek is impacted by naturally occurring sources of mercury and drainage from abandoned mines, and lower Stony Creek is affected by pesticide runoff and high temperatures. Black Butte Lake has also suffered water quality issues, with a toxic blue-green algae bloom occurring most recently in summer 2017. The watershed in between Stony Gorge and Black Butte Dams is highly impacted by erosion, both due to overgrazing by sheep and cattle, and due to the naturally erosive geology of the area.
Agriculture makes up most of the local economy, with the major crops being almonds, olives, oranges, wheat, and corn, and also dairy operations and pasture. The upper watershed historically had a significant logging industry, although the amount of timber harvested saw a dramatic decline in the 1990s and has remained low since then.
Geology Nearly all of Stony Creek's course is in Glenn County, where the landscape is divided into two major terranes, or crustal fragments that have accreted to the North American continent over millions of years. To the west is the Coast Range terrane, composed of folded, faulted marine rock from the Jurassic and Cretaceous periods (about 200–65 million years old). Rocks of the Franciscan assemblage, consisting mainly of metamorphosed basalts and greywackes, predominate in the Coast Range. The Franciscan rock is highly erosive and is the major contributor to Stony Creek's high sediment load. The Stony Creek Formation, composed mainly of conglomerate, sandstone and shale, is found further east in the foothill transition zone between the Coast Ranges and Sacramento Valley. The Stony Creek formation is considered the northernmost end of the Great Valley Sequence, and the inactive Stony Creek Fault, which runs parallel to and east of upper Stony Creek, marks the boundary between the two.
The Sacramento Valley terrane to the east is composed of sedimentary rock overlain by thick layers of fluvial sediments, mainly clay, gravel, sand and silt. About 450,000 years ago, Stony Creek's present outlet from the Coast Ranges was established, and the stream began building its large alluvial fan, or inland delta, stretching from the Coast Range foothills to the Sacramento River. The delta is composed of a variety of igneous and sedimentary rocks from the Franciscan assemblage. Stony Creek has changed its course across the delta multiple times, with the current channel being established only about 10,000 years ago. Until the creek was dammed in the 20th century, the fan was considered "active", or still in the process of being built by upstream sediments.
Ecology While the native grasslands and riparian habitats of the Sacramento Valley have been almost entirely replaced by agriculture, the foothill and mountain areas of the Stony Creek watershed have a diversity of plant communities. The lower foothills consist of grassland, valley oak, blue oak and blue oak-foothill pine woodland, and chaparral; higher in elevation, hardwood forests of interior live oak and black oak occur along streams, and Douglas fir, white fir, ponderosa pine, and sugar pine are abundant in the mid-elevation, mixed-conifer forests of the Coast Range. Red fir dominates above elevations of about , though only a small part of the watershed is that high in elevation. Most native perennial grasses in the watershed have been replaced by non-native annual grasses.
Upper Stony Creek is home to a variety of native and introduced fish species, including rainbow trout, hardhead, bass, catfish and carp. There are 28 fish species in lower Stony Creek, of which 13 are native. Historically, anadromous fish (salmon and steelhead migrated from the Pacific Ocean, and up the Sacramento River and Stony Creek to spawn. Dams now form an impassable barrier for fish migration to upper Stony Creek; changes in stream flow patterns and gravel mining in the old river bed have adversely affected spawning habitat in lower Stony Creek.
Historically, lower Stony Creek was a braided stream with a wide rocky bed, replenished each year by large volumes of sediment eroded off its watershed. The construction of Black Butte Dam in 1963 cut off 90 percent of sediment to the lower creek and has led to what has been termed the "hungry water effect", where Stony Creek continues to erode its banks while no new sediment is deposited. The erosion problem has been made worse by fluctuating water releases for irrigation. As a result, the creek bed has become narrower and deeper, reducing spawning habitat for salmon and creating ideal conditions for invasive giant reed (arundo) and tamarisk.
The Glenn County Resource Conservation District is undertaking an arundo and tamarisk removal program which includes both manual removal and chemical treatment. The U.S. Department of Agriculture has proposed a sediment management plan for the upper watershed which would reduce the amount of sediment flowing into reservoirs by 25 percent. In addition, there is a proposal to dredge gravel that has accumulated in Black Butte Lake and use it to replenish the streambed, improving habitat for native fish.
Human history The Native American population in what is now Glenn and Colusa Counties was approximately 10,000 before the first Europeans arrived. Most of the Native Americans spoke Wintuan languages, with the Nomlaki being the main people in the Stony Creek area. Native people inhabited independent villages, with only a loose central tribal structure that existed mainly to facilitate trade. Villages were either clustered along the Sacramento River or in foothill valleys like those of Stony Creek; due to a lack of water there were no settlements on the alluvial plain, which also served as a dividing line between the "river Indians" and "foothill Indians". In dry years, when forage was scarce at lower elevations, thousands of natives migrated to temporary settlements along upper Stony Creek. Although the Native Americans practiced no agriculture, they frequently set brush fires which promoted the growth of certain plants they gathered for food.