Hydrology of the lower Sacramento River starts at Shasta Dam, which was completed in 1944 and created the largest reservoir in the Central Valley Project system with a storage capacity of 4.5 million acre-feet. Additionally, since 1964, more than 1 million acre-feet of flow from the Trinity River has been exported each year to the Sacramento River Basin. This water is diverted from Trinity Reservoir through Lewiston and Whiskeytown Reservoirs, and into the Sacramento River upstream of Redding. Shasta Dam operations have altered the timing of peak flow and base flow in the Sacramento River. Prior to Shasta Dam, monthly flows in the river reflected runoff patterns associated with winter precipitation and spring snowmelt, with peak flows generally occurring in February, March, and April. Now, flows downstream of the dam are regulated and typically are lower in the winter season (when releases from the dam are reduced for flood protection) and higher in the summer (when water is being released for downstream irrigation needs). As an example, since 1963, mean monthly flows during July, August, and September in the river at Redding are 400% higher compared to summer flow prior to 1943. These CVP-related hydrology changes are most obvious directly below the dams and become less pronounced in the lower reaches of the Sacramento Valley because of inflow from tributary streams. Typical summer season flows in the Sacramento River are about 8,000 cfs at Red Bluff and 12,000 cfs at Verona just north of Sacramento. The Sacramento Valley can be broadly characterized as a flow-through system, in that most of the water not consumed for irrigation or other purposes eventually returns to the river via various tributaries or percolates to groundwater that recharges local aquifers. Winter floodflows in the valley still occur and are a major management issue. From Butte City downstream, flooding in the Sacramento River is controlled by an elaborate system of levees and bypasses. When river flows reach a certain height, water spills into the Colusa, Sutter, and Yolo Bypass channels in order to minimize risk of flooding to adjacent agricultural lands and major urban centers (including the city of Sacramento).
Groundwater is divided into the Sacramento Valley and Redding Groundwater Basins. DWR estimates that average annual groundwater use in the region is about 2.5 million acre-feet, and on average, groundwater accounts for approximately 31% of total water use. Historically, groundwater levels in the Sacramento Valley have remained steady, declining moderately during extended droughts and generally recovering to their pre-drought levels during subsequent wetter periods. In the DWR bulletin 11b-03, groundwater quality in the Sacramento River hydrologic region is described as “generally excellent.”
Water Quality Water quality protection for aquatic life, recreation, and domestic supply is a principal management issue in the Sacramento Valley. While numerous federal, state, and local agencies conduct water quality monitoring, the existing monitoring programs of DWR, RWQCB, and Department of Pesticide Regulation are of particular significance. These programs are discussed in more detail later in the monitoring section of this report. Use of agricultural chemicals on the almost 2 million acres of irrigated cropland in the Sacramento Valley is a concern with regard to potential aquatic life toxicity and impacts on domestic water supplies. In 2009, 8,600 growers, with 1.2 million acres of irrigated agriculture, conducted over 4,700 water quality analyses. Pesticides were analyzed in 95 water column samples collected at 12 different sites. To date, over 98 percent of the pesticide analyses performed were below detection. Other Sacramento Valley water quality issues relate to abandoned mines, urban runoff, and water management operations that affect streamflow, aquatic habitat, and water temperature. Primary water quality issues in the Sacramento Valley include:
Two vegetation types dominate the Sacramento Valley Subregion—agricultural cropland and riparian/wetland habitats.
Agricultural Lands—In the Sacramento Valley approximately 60 commercial crops are grown on approximately 2 million acres of irrigated farmland. Rice is the number one crop in the Sacramento Valley Region, accounting for 26% of the total agricultural acres. The next most prominent group is field crops (19%) followed by orchards (15%), pasture (11%), and grains (10%). In general, the lowlands of the valley primarily are planted in rice, rotated into winter cereal grains, or are permanent wetlands. Orchards generally are grown on alluvial soils near major rivers and tributaries and tend to be concentrated on the eastern or far western areas of the Sacramento Valley.
Riparian and Wetlands—Historically, the Sacramento River was bordered by up to 500,000 acres of riparian forest, with valley oak woodland covering the higher river terraces. In low-lying areas beyond the riparian and hardwood forests, there were vast seasonal marshlands that would transition to dry alkaline sinks during the summer. Beginning in the mid-1800s, agricultural conversion and urbanization aided by dams, levees, and channelization altered this riparian system to where currently there are approximately 24,000 acres of riparian habitat in the river corridor, less than 5% of the original amount. Depending on distance from permanent or seasonal water and stage of succession, native plant communities along the Sacramento River and tributaries can be grouped as:
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For the 10-year period 1998–2008, SRWP conducted water quality monitoring on the Sacramento River and a number of tributaries throughout the Sacramento Valley. In December 2006, SRWP prepared a Monitoring Program Summary Report. As stated in the conclusions of that report, SRWP’s monitoring program found that most sites analyzed meet water quality objectives and that the river is a high quality source for domestic and municipal use. Despite the legacy of contaminants from the early twentieth century mining era, metals are generally not a problem in the watershed, with the exception of mercury. Mercury and methylmercury levels are a health concern because they accumulate in the tissue of organisms and can be magnified up through the food chain. Organophosphate pesticide levels were found to be trending downward in response to restrictions on the use of diazinon and chlorpyrifos and resulting changes in their use in both agricultural and residential applications.
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The Sacramento River National Wildlife Refuge currently has 29 individual land parcels along a 77-mile stretch of the Sacramento River from Red Bluff to Princeton. Most of these units are partially or entirely open to the public for recreational activity and there is no access fee. The Refuge vision is to create a linked network of up to 18,000 acres of riparian and floodplain habitats, including forests, grasslands, freshwater marsh, and other aquatic habitats. This will be done through restoration techniques and working with other public and private partners. Refuge lands will help fulfill the needs of native fish, wildlife, and plants that have been affected by the significant loss of Sacramento River riparian habitat over the past century. It also will provide quality recreational opportunities including wildlife observation, environmental education, photography, hunting, and fishing.
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The Sacramento Valley is a unique landscape that includes state and national wildlife refuges, privately managed wetlands, rivers and streams that provide passage and spawning habitat for the state’s largest run of salmon and steelhead, and habitat for a wide variety of wildlife species. The river riparian corridor, the natural and managed wetland areas, and the nearly 2 million acres of agriculture lands all provide valuable habitat for wildlife species in the valley. Although specific management practices influence the value of rice lands, the mere presence of the approximately 500,000 acres of summer- and winterflooded area is highly important wetlands-like habitat to water-dependent bird species. Four runs of Chinook salmon occur in the Sacramento River with each run defined by a combination of adult migration timing, spawning period, and juvenile residency/migration periods. The presence of four seasonal runs in the Sacramento River (fall, late-fall, winter, and spring) lends it the uncommon distinction of having some salmon in its waters throughout the year.
Historically, large numbers of winter-run and spring-run Chinook salmon migrated through the Sacramento Valley to reach headwater areas with constant flow and cold water temperatures in the Upper Sacramento, McCloud, and Pit Rivers. Major water projects (e.g., Shasta Dam, Oroville Dam) blocked access to this part of the Sacramento watershed, and today only a few individual streams support spring-run salmon; the winter-run is restricted to the mainstem of the Sacramento River downstream of Shasta Dam. Winter-run salmon are federally listed as threatened and endangered, and spring-run are listed as threatened, as are Sacramento River steelhead trout. Currently, fall-run Chinook salmon are the dominant run; however, their numbers have dramatically declined, particularly in the last several years. As discussed in the Sacramento River Basin Overview section, there are major state and federal programs currently underway to restore both resident and anadromous fish populations in the Sacramento River, most notably, the Anadromous Fish Restoration Program being implemented as part of the Central Valley Project Improvement Act, and the DFG Salmon, Steelhead Trout, and Anadromous Fisheries Restoration Program. During the past two decades, water purveyors in the Sacramento Valley have been engaged in an agressive effort to enhance the passage of anadromous fish along the Sacramento River and it’s tributaries through the installation of fish screens on major diversions. This effort has led to the completion of state-of-the-art fish screens on almost all of the diversions that are larger than 200 cfs.
The seasonal and permanent wetlands of the Sacramento Valley are home to 60% of wintering and migrating waterfowl from the Pacific Flyway. There are six national wildlife refuges, more than 50 state wildlife areas, and large tracts of privately managed wetlands that support this migrating population. Winter fallow rice fields are also an important habitat component for ducks, geese, and other migrating waterfowl.
The cottonwood- and willow-dominated riparian forests along the Sacramento River have several characteristics that enable them to support an abundance and diversity of wildlife. Abundant food and cover, high structural diversity, and linear connectivity all contribute to making these riparian lands so important as wildlife habitat.
Agriculture is the largest industry in the Sacramento Valley with major crops that include rice, orchards (stone fruit and nuts), grain, pasture, tomatoes, and vineyards. The largest urban centers are Redding, Chico, Oroville, Marysville/Yuba City, Woodland, Davis, and Sacramento. In addition to the agricultural and food processing industries that are key employers in the region, important economic sectors include government, business and professional services, wood products, transportation, trucking and warehousing operations, and health care. Ethnic distribution is primarily White, followed by Hispanic, Asian/ Pacific Islander, African American, and Native American. Indian Trust Assets in the region include 12 rancherias, most of which are located in Shasta County. Six counties in the region are designated as disadvantaged communities based on median household income. The state capital, Sacramento is a city of ~500,000 and is the headquarters for numerous state and federal government agencies. Wastewater treatment for the city is the responsibility of the Sacramento Regional County Sanitation District. Major academic institutions in the region are UC Davis, CSU Chico, and CSU Sacramento.
The Sacramento River provides a major source of public recreation. On any summer weekend, thousands of boaters, rafters, and canoeists will be on the river between Redding and Sacramento. Sport fishing is popular, particularly for salmon and steelhead throughout the fall and winter, striped bass and sturgeon in the lower river, and resident rainbow trout between Redding and Red Bluff. The state and national refuges and private duck clubs offer high quality opportunities for waterfowl hunting.
There are many individual programs and plans in the Sacramento Valley Region that address water and watershed management. As discussed in the Sacramento Valley IRWM Plan, most of these individual programs are working toward one or more of the following principal management issues.
There are many federal, state, and local government agencies actively managing resources of California’s largest river system, including the collaboration of agencies that make up the CALFED Bay-Delta Program. The intent of the Roadmap is to highlight some of the more locally driven organizations working in the Sacramento Valley.
The Northern California Water Association (NCWA) was formed in 1992 to provide water users throughout the Sacramento Valley with a strong and united regional voice on California water policy. The NCWA mission is “to advance the economic, social, and environmental sustainability of Northern California by enhancing and preserving the water rights, supplies, and water quality.” in Northern California. More specifically, NCWA has a guiding principle that “Water districts’ and companies’ purpose is to provide landowners a reliable, affordable supply of irrigation, M&I and environmental water of suitable quality for reasonable use within its boundaries for as long into the future as water is needed for these purposes.”
Founded in 1996, the SRWP is a collaborative, consensus-based, nonprofit organization to “ensure that current and potential uses of the watershed’s resources are sustained, and where possible, enhanced, while promoting the long-term social and economic vitality of the region.” The program is represented by a 21-member board of directors that holds public meetings and oversees program activities. SRWP focus activities are (1) watershed monitoring (recently completed is a 10-year Sacramento River water quality study), (2) public education and outreach to inform stakeholders about the watershed they live in and promote good stewardship, and (3) support services to the large network of locally directed watershed management programs in the basin.
SRCAF evolved from Senate Bill 1086, which was passed by the State Legislature in 1986 and called for a management plan for the Sacramento River and its tributaries that would protect, restore, and enhance both fisheries and riparian habitat. The law established an Advisory Council composed of state and federal agencies, county supervisors, landowner representatives, water contractors, and fish, wildlife, and conservation representatives. SRCAF has a 21-member board of directors including a public interest representative and a landowner representative from the 6 agencies involved in activities along the river and a public interest representative appointed by the State Resources Agency. This program has produced 3 major guiding documents, the two listed, and the Good Neighbor Policy adopted in 2007. The SRCAF continues to promote and coordinate restoration-related activities along the Sacramento River and track the progress of ecosystem restoration projects.
The Trust is a nonprofit 501(c)(3) educational organization whose purpose is to protect and preserve the natural values of the Sacramento River and educate the public concerning ecologically viable farming methods and the need to preserve free-flowing rivers. Established in 1986 and currently operating under a nine-member board of directors and two-person staff, the Trust has worked for the past 26 years to support projects to improve ecological health of the river system.
The CALFED Bay-Delta Program is a collaborative effort among 23 state and federal agencies to improve water supplies and the health of the Bay-Delta system, which includes the Sacramento Valley. The program is currently governed by the Bay-Delta Authority that is comprised of state and federal agency representatives, public members, a member of the Bay-Delta Public Advisory Board, ex-officio legislative members, and members at large. An Independent Science Board provides guidance and input to the program. A Bay Delta Conservation Plan is being prepared to direct future restoration actions to improve reliability of water supplies and recover populations of threatened and endangered species. Since its beginning in 1994, the CALFED Program has funded and implemented numerous ecosystem projects in the Sacramento Valley Region.