Welcome to San Joaquin Marsh Reserve

Adjacent to UC Irvine, the San Joaquin Marsh is a remnant of a once extensive wetland mosaic with estuaries along the coast and freshwater marsh spanning the plains of inland Orange County.  It is also one of 39 reserves in University of California’s Natural Reserve System (NRS), the largest university-operated network of natural reserves in the world.

Freshwater is supplied to the marsh from San Diego Creek seasonally, feeding wetland depressions and ponds interspersed with fingers of willow riparian and bordered by uplands of coastal sage scrub and grassland.  Despite a history associated with agriculture and altered hydrology, the approximately 200 acre marsh has endured as a functioning ecosystem, supporting over 200 plant species, over 200 bird species, and providing refuge for the only remaining freshwater native turtle species in California, the Western Pond Turtle.

(recent recording of Ridgway’s Rails and chicks. Video by Barry Nerhus) 

The marsh is managed to maintain and enhance native biodiversity and ecosystem health for the purposes of research, education, and public and partner service programs. UC Irvine oversees and administers its management under UCI-NATURE, a program providing access to local and regional reserves and field-based assets.

A mosaic of ecological states provides opportunities for research and education in the thriving field of ecological restoration, an essential management tool for restoring portions of the land from a history of agriculture and duck ponds for hunting.  Our understanding of best management practices continues to evolve with our rapidly changing environment; including, emerging invasive species, increases in the intensity and frequency of drought, and rising sea levels.  Research and management come together to explore how we might plan for the intrusion of saltwater into a portion of the marsh.

The San Joaquin Marsh serves as a nexus for the University to engage in science base solutions to the County’s watershed challenges and threats to the vital Upper Newport Bay resource.  These efforts have implications as well for other vibrant economies positioned along coastlines world-wide.

San Joaquin Marsh shares ecological connections and partnerships with neighboring landowners managing natural lands and waters in Orange County watersheds. These connections extend the significance of research, teaching, and community engagement occurring within the marsh, in addition to leadership opportunities for students.

Proximity to the University and capacity for experimentation positions the marsh as a hub for environmental learning and research.  Levee roads and head gates maintain different sections of marshlands ponds, facilitating the manipulation of water levels and replications for experiments.  Environmental monitoring equipment includes three wells at 50, 100, and 150 feet, maintained by OC Watersheds, allowing for records of ground water quality, and an eddy covariance tower to monitor carbon balance and exchange.  The reserve does not currently maintain any laboratory facilities or on-site housing.

UCNRS San Joaquin Marsh Reserve Tour with Barry Nerhus (14:39)

More videos:

Invasive Species of Southern California with Barry Nerhus (3:08)

Natural History of the Western Pond Turtle with Barry Nerhus (47:34)

Wildlife and Research Flourish at the UCNRS San Joaquin Marsh – William L. Bretz (2:43)




San Joaquin Marsh Facts

Estab 1970
~ 200 acres
7-10 ft elevation

Download UCI Nature trifold brochure

Average Precipitation
12 inches/yr

Sept max: 86 F
Jan min 40 F
Annual mean 62 F


Faculty Advisor: Peter Bowler (Biological Sciences)

Faculty Advisor: Amir Aghakouchak (Engineering)