Central Coast Hydrologic Region

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Central Coast Hydrologic Region

The Central Coast Hydrologic Region (region) is divided by the Monterey County and San Luis Obispo County line into two planning areas, Northern and Southern. This report presents a general description of the area, water supplies and demands, and water resources management issues.


The Central Coast Hydrologic Region extends from southern San Mateo County in the north to Santa Barbara County in the south (Figure CC-1 Central Coast Hydrologic Region). The region includes all of Santa Cruz, Monterey, San Luis Obispo, and Santa Barbara counties, most of San Benito, and parts of San Mateo, Santa Clara, Ventura, and Kern counties. Many attributes define the Central Coast region including the diverse topography, microclimates, and the picturesque coastline, valleys, and communities that drive a thriving agricultural and tourism economy. The unique microclimates across the region are found in redwood forests, foggy coastal terraces, and chaparral-covered hills, green cultivated valley floors, stands of oak, warm and cool vineyards, and semi-arid grasslands. Most of the Central Coast region is within the southern Coast Range, extending from Monterey Bay in the north to Santa Barbara in the south.

The coastal part of the region begins in the north near the San Mateo-Santa Cruz county line and extends along the Pacific Ocean to the Santa Barbara-Ventura county line in the south. The coastline is dramatic, with prominent sea cliffs, bays, and coves, some of which merge into large, flat, coastal terraces that grade eastward into stream-cut canyons and craggy mountains. The region is full of oak-dotted, grass-covered hills and valleys.

The interior hydrologic boundary runs northwest to southeast, bound by and subparallel to the hilly topography created by the active San Andreas Fault Zone. Topographically, the extent of the Central Coast region is largely controlled by the northwest-trending southern Coast Range with peaks that attain elevations of 4,000 to 7,000 feet. These mountains include the Santa Cruz Mountains; the Diablo and Gabilan ranges; the coastal Santa Lucia range; the Temblor, La Panza, and Caliente ranges; and the Sierra Madre, San Rafael, and Santa Ynez mountains. The Santa Ynez Mountains in the southernmost part of Santa Barbara County are also part of the east-west trending Transverse Ranges.


The Central Coast Northern and Southern planning areas have geographic collections of individual and shared watersheds. The Monterey-San Luis Obispo county line serves as the boundary between these two planning areas, which are both further subdivided into hydrologically based detailed analysis units. All rivers within the region drain into the Pacific Ocean. Following is a summary of the descriptions of each planning area.

Northern Planning Area Watersheds

The Northern Planning Area contains all of Santa Cruz and Monterey counties, most of San Benito County, the southern part of Santa Clara County, and a small part of southern San Mateo County. The main rivers in the region are the San Lorenzo, Pajaro, Salinas, San Benito, Carmel, San Antonio, and Nacimiento. Coastal watersheds west of the northern Santa Lucia Range include the Little Sur and Big Sur rivers and numerous coastal streams, some of which are perennial.

The San Lorenzo River originates at the crests of the Santa Cruz and Ben Lomond Mountain ranges and enters the Pacific Ocean at Santa Cruz. The Pajaro River begins in southern Santa Clara County and is joined by Pacheco Creek, the San Benito River, and Tres Piños Creek. The Pajaro River watershed spans four counties. The river enters Monterey Bay and the Pacific Ocean west of Watsonville. The Pajaro River watershed is one of the Central Coast region’s largest and is well known for its productive agricultural soils and powerful flooding characteristics.

The largest watershed in the region is the Salinas River watershed, which drains more than 40 percent of the Central Coast region. The Salinas River originates in the La Panza Mountains of San Luis Obispo County and flows northward through the Salinas Valley to Monterey Bay, a length of approximately 170 miles. Major tributaries to the Salinas River are the Nacimiento, San Antonio, and Arroyo Seco rivers, all of which originate west of the Salinas River in the Santa Lucia Range. Other tributaries are the Estrella River and San Lorenzo Creek, which begin east of the Salinas River in the Cholame Hills and Gabilan Range, joining the river at King City.

The Carmel River watershed begins on the western slopes of the Sierra de Salinas. Numerous creeks join the Carmel River, which flows through Carmel Valley and into the Monterey Bay National Marine Sanctuary at Carmel Bay.

Southern Planning Area Watersheds

The Southern Planning Area contains all of San Luis Obispo and Santa Barbara counties, as well as a portion of northwest Ventura and a few square miles of Kern counties. The principal watersheds are the Upper Salinas, the Santa Maria—which includes the Huasana, Cuyama, and Sisquoc rivers—the San Luis Obispo, San Antonio, Santa Ynez, Carrizo Plain, and the Santa Barbara Channel Islands. As in the Northern Planning Area, coastal watersheds here are mostly short and steep. They range in size from 162 acres to 30,572 acres.

The Upper Salinas River originates in the La Panza Mountains of southern San Luis Obispo County and flows northward, joined by several creeks and the Estrella River before crossing over into the Northern Planning Area. The Santa Maria, San Antonio, and Santa Ynez watersheds drain to the Pacific Ocean through rivers that originate 10 or more miles inland to the east. The San Luis Obispo watershed consists of coastal streams that originate in the hills and mountains southeast of the Santa Lucia Range. The Carrizo Plain, just west of the San Luis Obispo-Kern county line, is a large semi-enclosed alkali ephemeral lake basin traversed by the San Andreas Fault. The Santa Barbara Channel Islands watersheds drain to the Pacific Ocean through streams and minor drainages on each of the islands.


Within the Central Coast region, the flora and fauna are varied and often unique, supported by ecosystems that reflect each area’s hydrology, climate, and geology. Distinct ecological sections are represented in the region: the Central California Coast, the Central California Coast Range, and the Southern California Coast, of which only Santa Barbara County is a part. Each of these ecological sections has ecosystems that support diverse, sometimes specialized, assemblages of plants and animals.

Watersheds in the Northern Planning Area contain a high level of habitat, climate, and geological variation. The Santa Cruz Mountains bioregion, best known for its redwood and Douglas fir forests, supports one of the highest concentrations of endangered species in California, including coho salmon. This bioregion is also home to Coast live oak, chaparral and manzanita shrub lands, coyote brush, and native California grasses. Unique to the area are plant communities such as sand hills and sand parklands found nowhere else in the world.

This biological diversity also characterizes the San Lorenzo River watershed. Human disturbance over the last 200 years has created significant, chronic impacts to plant communities, wildlife, and fisheries habitats.

Scientists recognize Santa Cruz County as an important center for biological diversity. Seven animal species are listed as being in danger of extinction, and at least three of these species are endemic to Santa Cruz. Eight plant species are federally listed as endangered, and six of the species considered to be rare or endangered are endemic. The northern Santa Cruz County planning region includes the southernmost range for coho salmon, and contains three of the five streams where these fish occur south of San Francisco. Santa Cruz County watersheds also support populations of steelhead trout, which are federally listed as threatened on California’s Central Coast. In addition, coastal watershed areas in the county have been designated as critical habitat for the California red-legged frog, listed as federally threatened.

The ecological subsection of Watsonville Plain-Salinas Valley contains the Pajaro and Salinas rivers, and the Elkhorn Slough. The landscape is predominantly alluvial plain, covered with stream-derived, rich soils. Woodlands contain Valley and Coast live oak, and riparian areas have scattered stands of cottonwood and willow.

The Pajaro River watershed supports a multitude of biotic habitats and special status plant and animal species, including 22 species that occur or potentially occur in the region and are listed as threatened or endangered under State or federal law.

The Salinas River watershed’s riparian habitat is widely distributed in narrow strands along the banks of the Salinas River but rarely exists as extensive, mature stands. The habitat has been reduced and fragmented by agricultural conversion, urban development, grazing, and flood control activities. Tributaries to the Salinas River provide natural habitat for steelhead trout.

Elkhorn Slough harbors one of the largest tracts of tidal salt marsh in California. This ecological area provides much-needed habitat for hundreds of species of plants and animals, including more than 340 species of birds. More than 7,000 acres of protected lands are in the Elkhorn Slough watershed. Moss Landing Wildlife Area is in Monterey County adjacent to Elkhorn Slough. There are 728 acres of salt ponds and salt marsh just north of Monterey. This is part of the largest unaltered salt marsh along the California coast.

The Santa Lucia Range contains canyons populated by Douglas fir and some redwood and stands of a variety of oaks and mixed conifers, including the Monterey pine; California sagebrush, chaparral, and manzanita shrubs are prevalent. The Monterey Peninsula includes a diverse assemblage of plant and animal species. A preliminary assessment in the region shows 121 special status species. Of these, 15 plant species and 10 animal species are formally listed as threatened or endangered under State or federal endangered species laws.

Watersheds in the Southern Planning Area in San Luis Obispo and Santa Barbara counties support a wide variety of landscapes including coastal chaparral; woodlands of Valley, Coast live, and Blue oak; mixed conifers; willows; and sycamores in riparian areas; manzanita; and grasslands.

San Luis Obispo County’s size and geographic diversity support a wide variety of landscapes including maritime chaparral, pine forests, semi-arid mountains, serpentine habitats, grasslands, and juniper and oak woodlands that provide habitat and migration corridors for a wide variety of native species.

The Carrizo Plain, east of the Cuyama River and the Caliente Range, contains 250,000 acres of native California grasslands—the largest single native grassland remaining in California. The plain’s ecosystem supports the largest concentration of endangered animal species in California. To date, the area has 24 special status plants, three of which are federally listed as endangered.

Santa Barbara County is located at a point of transition between the Southern California and Northern California ecozones and is characterized by rare plant assemblages. More than 1,400 plant and animal species are found in the county. Of these, 54 are federally or State-listed as threatened or endangered species (22 plant and 32 animal species), and another 60 species are considered rare or of special concern.

Several salt marshes occur in Santa Barbara County and provide habitat for a number of estuarine invertebrates and fish, migratory birds, and rare and endangered animal species.


The Central Coast region has a temperate Mediterranean climate characterized by mild, wet winters and warm, dry summers. West of the Coast Range, the climate of the region is dominated by the Pacific Ocean and characterized by small daily and seasonal temperature changes and high relative humidity. As distance from the ocean increases, the maritime influence decreases, resulting in a more continental type of climate that generates warmer summers, colder winters, greater daily and seasonal temperature ranges, and lower relative humidities. For example, on a summer day, the maritime influence on climate can be felt by traveling from Cambria to Shandon.

Naturally occurring microclimates are prevalent throughout the region, where the local topography and geography creates pockets of climate that are distinct from the surrounding area. Microclimates are beneficial, if not crucial, to the region’s agriculture and viticulture, providing both warm and cool environments for a broad spectrum of specialty crops such as wine grapes, fruits, nuts, and vegetables. The vineyard-growing areas throughout the region generally have summers that are long and cool due to the influence of the ocean. High-quality wine grapes thrive in this environment with moderate climate all summer, foggy mornings, bright sunshine through the afternoon, and very windy afternoons and early evenings.

Between 2005 and 2008, the average annual precipitation—usually rain—in the region ranged from about 12 to 42 inches. Most of the rain occurs between late November and mid-April. The average annual precipitation near Salinas is about 14 inches; Santa Cruz and Big Sur receive almost double that amount. Average annual precipitation in most of the Santa Cruz Mountains can exceed 50 inches. The southern interior basins usually receive 5 to 10 inches per year. The mountain areas receive more rainfall than the valley floors.


The Central Coast Hydrologic Region had 1.5 million people in 2005. About 4 percent of the state’s total population lives in this region, and 65 percent of the region’s population lives in incorporated cities. Between 2000 and 2005, the region grew by 65,515 people, a growth of 5 percent over the 5-year period. For historical population data, 1960–2005, see Volume 5, The Technical Guide.

In Water Plan Update 2009, population growth projections are based on future scenario assumptions. Discussion of the three scenarios used in this Water Plan and how the region’s population may change through 2050 can be found later in this report under Looking to the Future.

Senate Bill 18 (Chapter 905, Statutes of 2004) requires cities and counties to consult with Native American Indian Tribes during the adoption or amendment of local general plans or specific plans. A contact list of appropriate Tribes and representatives within a region is maintained by the Native American Heritage Commission. See also Box CC-2. A Tribal Consultation Guideline, prepared by the Governor’s Office of Planning and Research, is available online at http://www.opr.ca.gov/programs/docs/09_14_05%20Updated%20Guidelines%20(922).pdf

Land Use Patterns

The varied topography of the Central Coast region and its distance from California’s major population centers results in a landscape that is primarily pastoral and agricultural. Major economic activities include tourism, agriculture and agriculture-related processing, and government and service-sector employment.

Agriculture is a major contributor to both the economic and cultural identity of this region, distinguished by climates and rich soils that allow for specialty food and nursery crops as well as range pasture and dry-farmed grain. Irrigated crop acreage in the Northern Planning Area was 446,870 acres in 2005; crop acreage in the Southern Planning Area was 217,250 acres in 2005.

Federal lands in the region total more than 2 million acres and include Los Padres National Forest, Pinnacles National Monument, Channel Islands National Park, Carrizo Plain National Monument, Monterey Bay National Marine Sanctuary, Guadalupe-Nipomo Dunes National Wildlife Refuge, and the Salinas River National Wildlife Refuge. Military installations include Vandenburg Air Force Base, Fort Liggett, Camp Roberts, Camp San Luis Obispo, and Presidio of Monterey. State facilities include California Polytechnic State University and California State University Monterey, and nearly 60 parks, beaches, and monuments. The region’s economy benefits greatly from its parks, beaches, and forests, which draw millions of visitors each year.

The rate of urban change, or the conversion of farm and grazing land to urban or nonagricultural use, in the region between 2004 to 2006 varied from county to county, but as with the rest of California, the conversion trend steadily continues. (Table CC-1 Land use conversion of farm and grazing land to nonagricultural from 2004 to 2006).

Northern Planning Area

Northern Santa Cruz County is dominated by residential land use, including rural and mountain residential zoning, timber production, open space, agriculture, and a mix of commercial and special districts. The lower portions of the watersheds, close to Monterey Bay, are more urbanized with residential, commercial, and light industrial land use. Upper watershed land use consists predominantly of rural residential, timber production, open space, some mining, and limited agriculture. On the northern coastline, the coastal terraces are used for agriculture and grazing. Santa Cruz County is largely dependent upon tourism and recreation, which generate roughly $525 million annually. Agriculture is the county’s second largest industry, with a production value of

$491 million in 2007. The top five crops for Santa Cruz County in 2007 were strawberries, raspberries, miscellaneous vegetables, indoor cut flowers, and landscape plants. The southern area of the county, including Watsonville Sloughs, is a productive agricultural district yielding strawberries, raspberries, landscape plants, flowers, and vegetables. Northern coast agriculture includes brussel sprouts, strawberries, lettuce, and other specialty crops.

The agricultural production value of Monterey County in 2007 was $3.8 billion; and the prominent crops grown were leaf lettuce, strawberries, head lettuce, nursery plants, broccoli, and grapes. The predominant land use in the Salinas Valley is agriculture and rangeland, with discrete areas of urban development in the cities and towns along the Salinas River. The highest density areas of urban development are clustered to the north in the vicinity of Monterey Bay. Along the Salinas River are several urban and residential centers, including the City of Salinas in which resides more than 60 percent of the valley’s population. Near Seaside, more than 1,300 acres of the former military installation Fort Ord have been redeveloped into California State University, Monterey Bay.

The Monterey Peninsula and its surrounding areas are composed of a wide range of land uses that serve residential, commercial, industrial, recreational, and open space uses. Urban development is concentrated primarily in the coastal cities. Outside of the cities, low- to rural-density residential areas dominate. Land use in the 255-square mile Carmel River watershed includes wilderness, viticulture, grazing, recreation (golf courses and park areas), and sparse residential, suburban, commercial, and light industrial. Very little of the watershed is in traditional agricultural use. Resource conservation represents another important land use throughout the region, with parts of the planning area including the Ventana Wilderness and Los Padres National Forest.

The portion of the region in Santa Clara and San Benito counties includes agricultural, rural residential, and urban land uses. In San Benito County, the total agricultural production value of 2007 was $293 million; the top five crops were nursery stock, miscellaneous vegetables, wine grapes, bell peppers, and salad lettuce. For 2007, the total agricultural production value of Santa Clara County was $254 million; the top five crops were nursery plants, mushrooms, bell peppers, wine grapes, and grazing for steers and heifers.

According to county annual crop reports, more than 48,000 acres in the northern region are devoted to wine grapes, almost 90 percent of which are grown in Monterey County.

Southern Planning Area

The southern Central Coast is primarily pastoral and agricultural with scattered population clusters developed on coastal terraces and interior lowlands and valleys. Agriculture in the region has grown significantly in the last several years, thanks largely to vineyard expansions. As of 2008, about 58,000 active vineyard acres support about 280 wineries in the Southern Planning Area.

Agriculture comprises two-thirds of the land use in San Luis Obispo County with the majority of this acreage used for livestock grazing. The value of agricultural production in 2008 was $606 million, and the top five economic crops were wine grapes, broccoli, strawberries, cattle and calves, and vegetable transplants. As of 2007, planted vineyards covered about 36,000 acres, and harvested wine grapes increased to more than 20 percent of the county’s total agricultural production. Other land uses include rural lands, open space, and residential, commercial, and urban uses.

Major land use in Santa Barbara County includes agricultural preserves (land zoned for 100-acre or greater lot size) or other agriculturally zoned land. Less than 3 percent of the county is within incorporated cities, and 2 percent is within unincorporated urban areas. The value of agricultural production in 2007 was $1.1 billion. The top five crops were strawberries, broccoli, wine grapes, head lettuce, and cauliflower; lemons and avocados are also important crops for Santa Barbara. As of 2008, the county has more than 21,000 active vineyard acres, generating more than $100 million annually in wine grapes. Oil production continues offshore, but onshore production continues to decline.

Tribal Lands

Native American Tribal Communities may be federally recognized or otherwise. The federal government may set aside public lands for these tribes as reservations. In California these reservations are often named “Rancherias.” One interpretation of the Spanish term “Rancheria” is small Indian settlement.

In the Central Coast region, there is only the Santa Ynez Reservation, owned by the Santa Ynez Band of Chumash Indians and composed of less than 140 acres in Santa Barbara County. A resort casino was added to the reservation in 2004 and has since become a major source of tourism to the Santa Ynez Valley area.

Regional Water Conditions

The regional water conditions revolve around water supply and water quality, conditions which concern all of California. However, the Central Coast region does have unique water supply and quality challenges due to its geology, hydrology, and geography.

Environmental Water

Environmental water in the region consists primarily of minimum instream requirements for the Carmel River and the Nacimiento River. As of 2005, the Carmel River below the San Clemente Dam and Reservoir has an annual minimum instream flow of 3,620 acre-feet. Annual instream flow requirements for the Nacimiento River below the Nacimiento Dam are 18,099 acre-feet.

In San Luis Obispo County, a Habitat Conservation Plan has been developed for the upper watershed of the Arroyo Grande Creek. Once implemented, the plan calls for modified stream releases from Lopez Reservoir into the creek, with the intention of partially restoring and enhancing the habitat of steelhead trout and red-legged frogs.

Segments of the Big Sur River and the Sisquoc River have been designated as part of the national Wild and Scenic River system. For the Big Sur River, the North Fork and South Fork segments have unimpaired runoff from their headwaters to their confluence at the boundary of the Ventana Wilderness in Los Padres National Forest in Monterey County. In 2005, the runoff for that reach was more than 121,000 acre-feet. In Santa Barbara County, the Sisquoc River segment (mostly within the San Rafael Wilderness) has unimpaired runoff along a 33-mile stretch. The runoff in 2005 was more than 47,000 acre-feet.

Recent collaborative efforts organized by the Central Coast Wetlands Group (at Moss Landing Marine Labs) have initiated the development of a much-needed and comprehensive mapping and database program. Over time, this program may provide the data needed to better quantify the wetland and riparian water requirements in the Central Coast region.

The Central Coast Resource Conservation and Development Council continues to develop and participate in collaborative environmental water projects aimed at waterway and habitat restoration. Recent projects include Toro Creek, Pajaro River Watershed, and Sanborn Creek.

The Monterey County Water Resources Agency releases water from the San Antonio and Nacimiento reservoirs in routine, seasonal conservation releases to maintain flows on the Salinas River and recharge the river basin. Spillway modification construction has begun and upon completion will allow greater release of water from the dam during heavy-rain times and more flow on the Salinas River during dry times.

The San Lorenzo River Watershed Management Plan, adopted in 1979, established minimum streamflow requirements for salmonid migration, spawning, and rearing. The water rights for most surface water diversions include requirements for minimum bypass flows, including a year-round release (1 cubic foot per second) to Newell Creek from Loch Lomond reservoir. The City of Santa Cruz Water Department is working with the California Department of Fish and Game and the National Marine Fisheries Service to develop a habitat conservation plan to minimize any adverse impacts of aquatic habitat from operation of its water supply facilities.

Water Supplies

In California, both water supply and land-use planning are local responsibilities of utilities and city and county governments. Given its limited access to imported water, the Central Coast region has long-standing concerns over water supply issues. Water supply sources and conditions differ considerably across the rural counties.

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