Tijuana River Estuary

GENERAL			Source
Site	Tijuana Estuary
Map	Imperial Beach USGS 7.5' quadrangle
Location	Southwestern corner of San Diego County, between the City of Imperial Beach and Tijuana, Mexico.
Contacts	Tijuana Estuary Visitor Center (619) 575-3613
	Tijuana Estuary National Wildlife Refuge (619) 575-2704
Approximate Wetland Habitats Acreage	1,780		6
Approximate Historic Acreage	955 (intertidal saltmarsh, sand/mudflats, tidal channels and ponds shown on 1902 map.)		14

Ownership	Owner	Acres	Source
	City and County of San Diego	892	8, 10
	US Navy	551	8
	US Fish and Wildlife Service	505	8
	California Department of Parks and Recreation	418	8
	Private	166.24	8, 10

LAND USE			Source
Land Use Designation	National Estuarine Research Reserve; Open Space in the City of San Diego 1989 Progress Guide and General Plan; Resource Management in the Tia Juana River Valley Land Use Plan.		6
Onsite Use	Management and research activities associated with the National Estuarine Research Reserve and National Wildlife Refuge. There is also a state park and small leased areas in agriculture and residential use. Equestrian facilities and trails are well established in the valley. The river has received untreated sewage for extended periods intermittently since the 1930's. The area is traversed by both illegal immigrants and the Border Patrol, Naval helicopter training occurs overhead.		4, 6, 10
Historic Use	Agriculture, gravel extraction, stormwater discharge, and military facilities; sewage oxidation ponds and discharge operations in the northern part of the estuary were abandoned by 1970; the valley has a long history of equestrian use.		4, 10
Adjacent Use	The City of Imperial Beach and a military airport lie immediately to the west and north; to the east and south are agricultural and sand and gravel operations, and the Tijuana River Valley Open Space Park; the international border crossing is southeast of the estuary.		4
Historic Adjacent Use	Uses of surrounding areas included agriculture, military exercises, horse breeding facilities, and open space.		4

HYDROLOGY			Source
Tidal Influence	The tidal prism has been reduced by an estimated 80% since 1852; in 1987 the volume was calculated to be 250 ac-ft. The ocean inlet is described as being relatively shallow, it is also substantially free of structural constraints.		4, 6
Wetland Watershed Area	1700 sq miles; 1245 in Mexico and 455 in the US		6

Tributaries and Flow	Tributary	Flow
	Tijuana River	Historically seasonal, recent sewage discharges have resulted in year-round flows (1994 est 42 mgd). A 1994 report cites peak flow estimates ranging from 30,000-35,000 cfs for 25-yr and 65,000-90,000 for 100-yr.	2, 3
Dams	There are 3 dams in the watershed controlling 78% of the area; in the US, Morena was built in 1912 and Barrett in 1922; in Mexico, Rodriguez was built in 1936.		4
Other Sources	An unconfined aquifer exists in the alluvial fill underlying the river valley; its capacity is 65,000 acre-feet; in the absence of flows from Tijuana, groundwater may flow into the river channel and has ponded when the aquifer is full.		3

WATER QUALITY			Source
General	Raw sewage has been discharged to the River and side canyons intermittently for 50+ years, making flows perennial from 1980 to 1991; 1983 and 1985 river samples found high total coliform; Nov 1989-Apr 1990 study of the estuary found nutrient levels at the low end of the range found in secondary treated wastewater. A 1990 study estimated 900 lbs lead, 290 lbs cyanide go into the river each year. The Estuary was listed in 1994 as an impaired waterbody; the draft list for 1996 cites selected standards exceeded for coliform, pesticides, eutrophication, metals, trash and debris. Designated Beneficial Uses of the Estuary - Rec1, Rec2, Comm, Biol, Est, Wild, Rare, Mar, Migr, Shell.		4, 6, 3, 2, 11, 12, 13
Dissolved Oxygen (DO)	Summary of Nov 1989-Apr 1990 study reported a range of mean bottom concentrations for the estuary of 3.3-8.1 ppm with ranges varying throughout the estuary; the widest was found along Old River (large southern arm). Time of sampling was not indicated.		6
	The range of mean bottom temperatures was 16.9 - 21.5 C.
Water Salinity	Summary of Nov 1989-Apr 1990 study reported variation throughout the site; averages of 27 ppt near the mouth, 31 ppt for the channel with the greatest tidal prism; and a range of 1-6 ppt at Hollister St Bridge (.5 mile east of Rsv bdy).		6
	The study concluded that sewage flows had an extensive dilution effect on the Estuary.
Sediment	Substantial during flooding; between 1852 and 1986 an estimated 200 acres of intertidal wetland were filled due to sedimentation. Reservoirs reduce the sediment load by an estimated 50% in low-flow years, and by less than 20% in high-flow years.		3, 6

Soil
Soil	Much of the eastern part of the site is Chino silt loam, Tujunga sand is found adjacent to the River and in the NE part of the Reserve, a small area of Visalia sandy loam lies in the SE part of the Reserve, much of the western part is tidal flat.		6

Habitat	Acres	Vegetation	Source
Mudflat/Tidal channel	206	1992 rpt- phytoplankton - dinoflagellates, diatoms, filamentous blue-green algae, unidentified unicells; also sea lettuce and Enteromorpha (both green algae).	4
Salt marsh	615	1992 rpt - 17 of 22 "well-known" native salt marsh plants occur at the estuary including salt marsh bird's beak+ ; cordgrass, pickleweed, glasswort, and saltgrass were dominant.	4
Salt panne	70	1992 rpt - this habitat is usually unvegetated; ditch grass and algae grow in winter when the pannes hold water, patches of glasswort grow interspersed among the pannes.	4
Brackish/freshwater marsh, scattered	30	1992 rpt - cattails, bulrush dominant; ditchgrass can become abundant seasonally if standing water accumulates.	4
Riparian	248	1992 rpt - there is a gradient with decreasing soil and water salinity moving east; pickleweed, saltgrass,water wally, sandbar willow, cottonwood, various willows, and mulefat dominate along the gradient.	4
Transition	610	1984 survey identified a gradient with decreasing elevation and some overlap; Australian saltbush*, California buckwheat, golden bush, laurel sumac, saltgrass, alkali heath, glasswort, and salt cedar, dominants along the gradient.	5
Upland	822	1991 - Mixed Transition/Disturbed, Disturbed, Coastal Dunes and Beaches, Coastal Sage communities also present	6

ANIMAL USE			Source
Birds	Winter 1988/89 survey - 90 species total, 63 waterbird, 9 raptor, 18 upland; 9 species of special concern. 1995 - 61 pr light-footed clapper rail#; 1994 - 5 active snowy plover+ nests; 1991 - 303 pr Belding's Savannah sparrow#.		6, 16, 17, 18
Fish	Sep 1986 - Dec 1989 sampling (gear not specified) collected 21 species from 15 families; arrow goby dominant, also topsmelt and California killifish; dominance shifted during the sampling period from co-dominance by topsmelt and arrow goby.		4
Benthic Invertebrates	Various studies since 1969 document changes in community structure after catastrophic events; Sep 1986 - June 1988 sampling of north channels collected 58 taxa of polychaetes and bivalves, also the California ghost shrimp; highest bivalve densities were at the deepest site also farthest from sewage inflow; Capitellids and Spionids were the dominant polychaetes.		4
Insects	Fall 88 - Spr 89 survey of dune, Salicornia marsh, transition and upland found 16 orders; beetles, springtails, flies, leafhoppers and planthoppers, bees and wasps, butterflies and moths were most abundant; salt marsh wandering skipper butterfly+ was present, also globose dune beetle+ on dunes.		6
Other Wildlife	Sep 88 - June 89 survey of reptiles and amphibians found 13 of 25 - 30 species expected according to the habitats onsite - 4 species of frogs, 6 of lizards, and 3 of snakes, including the African clawed frog* and the bullfrog*; also the San Diego coast horned lizard+ in dunes. Evidence of 16 mammal species was found Nov 1988-May 1989,10 of those on the marsh; no Pacific pocket mice+. Domestic dogs and long-tailed weasel are seen frequently.		6
Special Status Species	Salt marsh bird's beak, salt marsh wandering skipper, light-footed clapper rail, Ca brown pelican, Ca least tern, Amer peregrine falcon, Belding's Savannah sparrow, western snowy plover, reddish egret, long-billed curlew, large-billed Savannah sparrow; globose dune beetle on dunes.		6

OUTLOOK			Source
Enhancement Status	Phased tidal restoration program prepared in 1991 includes restoration of approximately 495 acres of tidal wetlands and riparian habitat and tidal channel improvements; implementation to be guided by adaptive management, with monitoring and evaluation of each phase informing the next; the first phase, which includes a 20-acre model project, was in final engineering and design stage, Fall 1995.		6, 10
Watershed Management	Parts of a phased project to provide secondary treatment and an ocean outfall for raw sewage are at various stages - one is under construction, another is in environmental review. A binational GIS mapping project for the watershed was begun in 1994, with the goal of developing basin-wide policies on resource management; data could be incorporated into a complementary effort to gain biosphere reserve status for the watershed, the long-term goal of which is a management plan for the entire watershed.		1, 3, 10
Pressure	Uncertain duration of continued raw sewage, sewer flows and associated effects of contamination and modified freshwater inputs; effect of dams; sedimentation; flood control concerns; "cross-country" travel by immigrants and Border Patrol.		4, 6, 2

Comments
SOURCES
1	Institute for Regional Studies of the Californias. 1995. Identifying priorities for a Geographic Information System (GIS) for the Tijuana River Watershed: Applications for land use, planning, and education. 93 pp.
	A summary of a workshop funded by NOAA to San Diego State University and El Colegio de la Frontera Norte for the development of a binational geographic information system (GIS) for the Tijuana River
	watershed. The document provides an overview of the topics discussed at the workshop, which included GIS case studies and focus groups. Includes a list of participants. Detailed papers are not included in the document.
2	BSI Consultants, Inc. 1994. Two alternatives report: Tijuana River Valley flood control and infrastructure study. Prepared for the City of San Diego Tijuana River Valley Task Force. Approximately 58 pp. and appendices.
	Evaluates options for flood control and protection of infrastructure in the Tijuana River Valley in terms of property protection, health and safety issues, protection/enhancement of biological resources, recreation, agriculture, border patrol activities, ground water issues. Also assesses impacts of two alternatives. Based on existing information and new HEC-2 hydraulic analysis.
3	City of San Diego. 1994. South Bay tunnel and ocean outfall: focused supplement to the International Boundary and Water Commission (IBWC) international wastewater treatment plant and outfall facilities final environmental impact statement. 300 pp.
	Analyzes environmental impacts of a tunnel under the Tijuana Estuary connecting to a seafloor pipeline. The outfall would discharge effluent from the international wastewater treatment plant and the City of San Diego's
	proposed South Bay and Otay Valley water reclamation plants. Provides existing setting information on oceanography, hydrology/groundwater, cultural resources, geology, biological resources, public health,
	land use, noise, visual quality, odor, and air quality. Incorporates existing information from a variety of reports. Extensive references.
4	Zedler, J.B., C.S. Nordby, and B.E. Kus. 1992. The ecology of Tijuana Estuary, California: a National Estuarine Research Reserve. NOAA Office of Coastal Resource Management, Sanctuaries and Reserves Division, Washington D.C. 151 pp.
	An updated version of the 1986 Estuarine Profile (Biological Report 85(7.5)) by Joy B. Zedler and Christopher S. Nordby. Synthesizes and interprets existing information on the Tijuana Estuary's
	vegetation, algae, birds, fishes, and invertebrates. Profiles the Tijuana Estuary in terms of its natural history, ecological communities and ecosystem functioning, analyzes the role of disturbances in
	modifying saltmarsh structure and function, and discusses adaptive management and restoration. Includes information on physical changes. Incorporates existing information from a variety of reports.
5	Zedler, J.B. and C.S. Nordby. 1986. The ecology of Tijuana Estuary, California: an estuarine profile. U.S. Fish and Wildlife Service Biological Report 85 (7.5). 104 pp.
	Synthesizes and interprets existing information on the Tijuana Estuary's vegetation, algae, birds, fishes, and invertebrates. Profiles the Tijuana Estuary in terms of its natural history, ecological communities and ecosystem functioning,
	analyzes the role of disturbances in modifying saltmarsh structure and function, and discusses adaptive management and restoration. Includes information on physical changes.
	Incorporates existing information from a variety of reports. Report was updated in 1992.
6	ENTRIX, Inc., PERL, and Philip Williams and Associates, Ltd. 1991. Tijuana Estuary tidal restoration program draft EIR/EIS. Volumes I-III. Prepared for the State Coastal Conservancy and U.S. Fish and Wildlife Service. 263 pp and appendices.
	A programmatic environmental impact statement/environmental impact report (EIS/EIR) on a proposed 495-acre tidal restoration program for the estuary. Volume II, the hydrological appendices, includes discussions of the geomorphology of the estuary,
	river and barrier beach; tidal hydrodynamics, entrance channel closure conditions; hydrologic and geomorphic analyses; and technical memoranda. Volume III, additional appendices, includes sediment
	sampling results, biological technical reports, and a cultural resources report. Original fieldwork was conducted for the biological technical appendices.
7	California State Polytechnic University, Pomona for the County of San Diego, Department of Parks and Recreation. 1989. A Management Framework for the Tijuana River Valley. 117 pp.
	The purpose of the study is to provide a management framework for park-oriented development of the Tijuana River Valley. The first section contains an overview of the major issues, along with discussion of the implications of these concerns
	for the management of this landscape. Analyses address regional context, history, hydrological, geological and biological information, and human use considerations. The section on biology
	contains material on vegetation, wildlife, and ecosystem relationships. Incorporates existing information from a variety of reports. Includes extensive references.
8	James Dobbin Associates Incorporated. 1986. Tijuana River National Estuarine Sanctuary management plan. Prepared for the California Coastal Commission, NOAA, and Tijuana River National Estuarine Sanctuary Management Authority. 183 pp.
	Discusses goals and objectives for the Sanctuary including protection of significant estuarine resources, improvement of the overall health of the estuarine ecosystem, compatible multiple uses, public education,
	and a management-oriented research program. Describes the administrative framework for Sanctuary management, and summarizes the policies and regulations that guide use and protection of the Sanctuary. Also identifies
	on-site programs to be implemented over a fiveto ten-year period. Incorporates existing information from a variety of reports.
9	Zedler, J.B. 1982. The ecology of southern California coastal salt marshes: a community profile. U.S. Fish and Wildlife Service, Biological Services Program, Washington, D.C. FWS/OBS-81/54. 110 pp.
	Describes the structure and functioning of California's coastal salt marshes south of Pt. Conception. Summarizes the physiographic, hydrological, and climatic setting, the resulting vegetative communities and their roles in
	overall marsh functioning. Faunal communities are also described. Discussion includes analysis of research data from specific sites and forwards conceptual models of marsh functioning.
10	Personal communication. State Coastal Conservancy, Karyn Gear June 14, July 20, 1995; Jim King July 21, 1995.
11	San Diego Regional Water Quality Control Board. 1994. Water quality control plan for the San Diego basin. Approximately 225 pp. and appendices.
	The plan designates beneficial uses and associated water quality objectives for inland surface waters, coastal waters, reservoirs and lakes and ground water in San Diego County. It includes a discussion of applicable policies and statutory
	requirements and identifies measures for achieving water quality objectives. It also describes ongoing monitoring and assessment programs. Appendices contain summaries of regional growth forecasts and criteria for organic and inorganic constituents.
12	State Water Resources Control Board. 1994. List of impaired water bodies.
	Developed as part of the Water Quality Assessment of the State's major waterbodies. Separate lists are developed to rate waterbodies as Good, Intermediate, Impaired or Unknown Quality. Impaired waters are those not expected to attain or maintain
	water quality standards. The state list is a compilation of those developed by the nine regional boards. Lists of impaired water bodies are also known as 303(d) lists as they meet a requirement of section 303(d) of the federal Clean Water Act.
13	San Diego Regional Water Quality Control Board. 1996. Draft 303(d) list.
	A proposed list of waterbodies in the San Diego Basin that do not or are not expected to attain water quality standards after application of required technology-based controls. Specifies selected beneficial uses and criteria assessed,
	and the percentage of samples in which criteria were exceeded. It also identifies waterbodies for which previous assessments are no longer applicable.
14	San Diego Unified Port District and the California State Coastal Conservancy. 1989. South San Diego Bay enhancement plan. Four volumes. 490 pp. and appendices.
	Report outlining natural resource enhancement opportunities in San Diego Bay south of the Sweetwater River channel in terms of engineering feasibility, regulatory requirements, and potential for Port development mitigation.
	Includes review of existing literature on natural resources values of area, comprehensive field inventory of natural resources emphasizing invertebrates, fish, birds, and additional studies of saltmarsh habitats, eelgrass resources, and
	selected environmental variables. Prepared by Michael Brandman Associates. Appendices compile data from field studies.
15	MEC. 1993. San Dieguito Lagoon restoration project regional coastal lagoon resources summary. 56 pp and appendix.
	This report provides a summary of habitat types, fish, bird and benthic invertebrate populations at 16 coastal wetlands south of Anaheim Bay. It is a synopsis of primarily existing information; sources used in identifying and quantifying
	habitat types include aerial photographs taken in early 1993. Discusses restoration of habitats at San Dieguito Lagoon given present and historic conditions of other coastal wetlands in the region. This report was prepared as part of the
	San Dieguito Restoration Project undertaken by Southern California Edison to mitigate for damage to coastal marine resources from the operation of the San Onofore Nuclear Generating Station.
16	Zembal, Richard. 1995. Status and distribution of light-footed clapper rails in California, 1980-1995. Preliminary report to the California Department of Fish and Game. 28pp.
	Results of the 1995 survey of breeding light-footed clapper rails in California. The report incorporates data from 15 years of annual surveys and discusses population trends for the region and at each of 36 sites censused. Trends are tied to
	ecological conditions at each site and the author identifies possibilities for improving habitat.
17	U.S. Fish and Wildlife Service. 1991. A survey of the Belding's savannah sparrow in California, 1991. Report to the California Department of Fish and Game. 24 pp. and survey site maps.
	Report on a survey for territorial Belding's savannah sparrow at 34 marshes between southern Santa Barbara county and the border with Mexico. Results are discussed within the context of previous years' data and recommendations are provided
	for further study and habitat improvements. The survey was carried out to provide an update on population data and to evaluate habitat conditions.
18	National Biological Survey for the Department of Fish and Game and US Fish and Wildlife Service. The status of western snowy plovers in San Diego County. 1994. 16 pp.
	The overall objective of this study was to determine the use of southern California's coastal wetlands habitats by western snowy plovers during the
	breeding and wintering seasons. The ability of the wetlands to support viable populations of western snowy plovers will be evaluated at the end of the research. This report includes the results of the first year of a three year survey.

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