Monitoring and Modeling of Water Quality in the Tijuana River Watershed

1. Purpose and Objectives: This project is an interdisciplinary research effort between the Department of Geography and the Graduate School of Public Health at San Diego State University (SDSU) and the Facultad de Ciencias Quimicas at the Universidad Autonoma de Baja California (UABC), Tijuana, to monitor stormwater quality and develop a conceptual model of non-point source pollution in the Tijana River Watershed. The objectives of this work are to characterize the spatial and temporal variability of stormwater quality; to model the interaction of landuse, population, and urbanization on stormwater quality; to use GIS technologies to explore and display the spatial dimensions of this interaction; to identify critical areas of surface water contamination; and to advance suggestions for future planning, management, and other policy efforts to address the water quality problems in the basin.

2. Funding: $81,659 SCERP FY96 Funds (EPA).

3. Partners: San Diego State University, Universidad Autonoma de Baja California, Tijuana

4. Description: The Tijuana River Watershed is a binational watershed on the westernmost portion of the US/Mexico border, encompassing much of the Municipality of Tijuana in Mexico and portions of the City and County of San Diego in the United States. The basin’s hydrology contains three surface water reservoirs, various flood control works, and an estuarine research reserve protected by the U.S. federal government; these elements yield transboundary and cross-cultural water resource management challenges. Inadequate infrastructure for the collection, treatment, and disposal of wastewater originating in Tijuana has long plagued the Municipality, as wastewater flows have chronically outpaced the ability of the infrastructure to handle them. Gravity and topographic regime of the region have allowed transboundary surface water pollution to negatively impact the lower reaches of the watershed, posing risks to human and environmental health on both sides of the border. Stormwater and other wet weather flows are particularly important in the transmission of surface water pollution in the basin; accordingly, we focus on these flows for the purposes of this research. Outcomes of this work include a detailed survey of the variability of stormwater quality, robust GIS output describing this variability, and a conceptual model of the interaction of landuse, population, and urbanization on stormwater quality. Additionally, a set of recommendations of management practices and planning options to improve the quality of stormwater will be proposed.

5. Status: Ongoing

6. U.S. Contacts: Richard Gersberg, San Diego State University, (619) 594-5423 Chris Brown, San Diego State University, (619) 594-5423 Paul Valdez, EPA Region 9, (415) 744-1168