Chino Basin

Chino Basin
Name	Chino Basin
Location	Inland Southern California
Country	United States
State	California
Counties	San Bernardino County, Riverside County, Los Angeles County
Cities	Ontario, Chino, Chino Hills, Upland, Pomona
Area km2	930
Basin type	Closed basin (endorheic) / groundwater basin

Chino Basin The Chino Basin is an endorheic basin in Inland Southern California occupying parts of San Bernardino County, California, Riverside County, California, and Los Angeles County, California. It includes urban centers such as Ontario, California, Chino, California, Chino Hills, California, and Upland, California and forms a major groundwater resource underlying the Pomona Valley. The basin intersects with regional systems including the Santa Ana River watershed, the Los Angeles River watershed, and engineered facilities such as the California State Water Project and the Colorado River Aqueduct.

Geography and Hydrology

The basin is bounded by the San Gabriel Mountains, the San Bernardino Mountains, and the Santa Ana Mountains, with alluvial fan deposits from tributary channels such as Mill Creek (San Bernardino County), San Antonio Creek (San Bernardino County), and Day Creek. Surface drainage historically collected in lowlands around the former Chino Dairylands and seasonal wetlands near Don Jan Pond and Hydes Reservoir, while modern channelization by agencies like the U.S. Army Corps of Engineers and the California Department of Water Resources altered flows. Groundwater occurs in stacked alluvial aquifers recharged by local recharge from the Santa Ana River and imported flows from the Metropolitan Water District of Southern California and the Colorado River. Geologic controls include bedrock from the Peninsular Ranges and faults of the Chino Fault system and the nearby San Andreas Fault complex.

History and Indigenous Presence

Indigenous peoples of the basin included the Tongva, the Serrano, and the Cahuilla who utilized tributary riparian corridors, springs, and marshes for seasonal camps and trade routes connecting to the Gabrielino-Tongva cultural sphere. Spanish colonial expeditions such as those led by Gaspar de Portolá and missionization by the Mission San Gabriel Arcángel reshaped land use through cattle ranching and the Mexican-era Rancho San Antonio (González) land grant patterns. American-era developments included the arrival of the Atchison, Topeka and Santa Fe Railway and agricultural transformations tied to the California Gold Rush’s population shifts and later California citrus industry expansion.

Water Resources and Groundwater Management

The basin is managed by entities including the Chino Basin Watermaster, the Santa Ana Watershed Project Authority, and local water districts like the Inland Empire Utilities Agency and the Three Valleys Municipal Water District. Groundwater banking, conjunctive use with surface imports via the Metropolitan Water District of Southern California, and recharge projects using spreading grounds and recycled water from agencies such as the Orange County Water District play central roles. Historic contamination incidents involving perchloroethylene and trichloroethylene from industrial and agricultural sources led to site remediation overseen by the California State Water Resources Control Board and the United States Environmental Protection Agency. Legal frameworks influencing allocations have included precedents set under state adjudications and compacts invoked by entities similar to the California Supreme Court in water rights disputes.

Ecology and Wildlife

Riparian remnants and constructed wetlands support species associated with southern California savanna and marsh habitats, including birds documented by organizations like the Audubon Society and National Audubon Society. Species observed in basin wetlands and flood basins include migratory waterfowl on the Pacific Flyway, raptors using urban-edge habitat adjacent to Chino Hills State Park, and native plants such as those cataloged by the California Native Plant Society. Threatened and sensitive species with regional relevance include the Coastal Cactus Wren and species protected under the Endangered Species Act and California’s Natural Community Conservation Planning programs. Invasive species management involves coordination with the California Invasive Plant Council and local conservation districts.

Human Use and Urban Development

Agriculture—historically dairies and citrus groves—and later suburbanization shaped land use. Major infrastructure includes the Ontario International Airport, the Interstate 10, Interstate 15, and state routes such as State Route 60 (California), which facilitated logistics in the Inland Empire (California). Urban growth produced sprawling residential developments, industrial parks, and retail centers governed by municipal planning departments of Ontario, California and Chino, California. Land planning intersects with regional initiatives such as the Southern California Association of Governments and transportation planning by the San Bernardino County Transportation Authority.

Environmental Issues and Restoration Efforts

The basin faces groundwater overdraft, salt intrusion, nitrate contamination, and legacy organic solvent plumes requiring remediation by the Environmental Protection Agency and state agencies. Restoration work involves constructed wetlands, stormwater capture projects under programs like the Proposition 84 (California) bond-funded initiatives, and habitat enhancement coordinated with the California Department of Fish and Wildlife. Collaborative efforts by stakeholders including the Chino Basin Watermaster, local universities such as the University of California, Riverside, and non-profits including the Nature Conservancy support research, monitoring, and pilot projects for recharge, water recycling, and ecosystem restoration. Ongoing litigation and policy dialogues reference statutes such as the California Environmental Quality Act and regional planning instruments administered by the Southern California Coastal Water Research Project.

Category:Basins of California Category:San Bernardino County, California Category:Rivers of Southern California