Hyperspectral characterization of wastewater in the Tijuana River Estuary using laboratory, field, and EMIT satellite spectroscopy

Elsevier | May 8th, 2025

Hundreds of millions of liters of untreated wastewater are discharged into the Tijuana River annually, impacting communities on both sides of the US-Mexico border. Curren

Hundreds of millions of liters of untreated wastewater are discharged into the Tijuana River annually, impacting communities on both sides of the US-Mexico border. Current monitoring methods are resource-intensive and limited in coverage. Optical satellite imaging may enable broader spatiotemporal monitoring, yet retrievals of bacterial concentrations and other key water quality indicators remain challenging. Here we investigate the utility of spectroscopic sensors to monitor the presence of wastewater in this estuarine-coastal system, as a proxy for bacterial concentrations and other water quality parameters. We prepared dilutions of untreated wastewater and uncontaminated seawater, measuring visible through shortwave infrared (VSWIR; 350–2500 nm) reflectance spectra of each sample. At high wastewater concentrations, a distinct spectral feature centered near 620 nm strongly correlated with paired water quality measurements (R2 ≥ 0.97, p-value < 0.01). This feature is additionally observed in multispectral resolution, in field observations, and in hyperspectral satellite imagery. An example application of plume mapping with this feature is presented, representing one of the earliest adoptions of EMIT hyperspectral satellite imagery for water quality monitoring. These results are promising for the use of spectroscopic sensors to map and monitor wastewater pollution in the Tijuana River Estuary and potentially, similarly polluted coastal and estuarine systems.

Identification of Bacteria in Groundwater Used for Domestic Supply in the Southeast San Joaquin Valley, California, 2014

U.S. Geological Survey (USGS) | June 22nd, 2021

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane filtration method for the chromogenic-/-fluorogenic detection of total coliforms and Escherichia coli, was used for samples collected January to April 2014 from 42 domestic wells in the southeastern San Joaquin Valley. The wells were sampled as part of the Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP), a cooperative study between the U.S. Geological Survey and the California State Water Resources Control Board. Polymerase chain reaction analysis and sequencing of deoxyribonucleic acid (DNA) were used for 34 target and nontarget colonies that grew on the MI media from samples collected from 13 of the domestic wells to identify what genera of bacteria could exist in groundwater used by domestic wells. Gene sequences obtained using the Sanger method were entered into the basic local alignment search tool (BLAST) database, and 17 genera of bacteria were identified. Of these, 13 genera contain species that are human pathogens or opportunistic human pathogens. All the genera that include human pathogens are naturally present in soil, plants, or water; one of the pathogens also can be found in fecal matter. Six of the human pathogens were from non-target colony growth on the MI media. Target and non-target microbial growth on MI media are indicators of the possible presence of pathogenic bacteria even if the bacteria naturally are from soil rather than from a fecal source.

Identification of Bacteria in Groundwater Used for Domestic Supply in the Southeast San Joaquin Valley, California, 2014

U.S. Geological Survey (USGS) | June 22nd, 2021

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane

Groundwater is an important source of drinking water in California. Water-borne diseases caused by microbial contamination are a growing concern. The MI test, a membrane filtration method for the chromogenic / fluorogenic detection of total coliforms and Escherichia coli, was used for samples collected January to April 2014 from 42 domestic wells in the southeastern San Joaquin Valley. The wells were sampled as part of the Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP), a cooperative study between the U.S. Geological Survey and the California State Water Resources Control Board. Polymerase chain reaction analysis and sequencing of deoxyribonucleic acid (DNA) were used for 34 target and nontarget colonies that grew on the MI media from samples collected from 13 of the domestic wells to identify what genera of bacteria could exist in groundwater used by domestic wells. Gene sequences obtained using the Sanger method were entered into the basic local alignment search tool (BLAST) database, and 17 genera of bacteria were identified. Of these, 13 genera contain species that are human pathogens or opportunistic human pathogens. All the genera that include human pathogens are naturally present in soil, plants, or water; one of the pathogens also can be found in fecal matter. Six of the human pathogens were from non-target colony growth on the MI media. Target and non-target microbial growth on MI media are indicators of the possible presence of pathogenic bacteria even if the bacteria naturally are from soil rather than from a fecal source.

Identification of fresh submarine groundwater off the coast of San Diego, USA, using electromagnetic methods

Hydrogeology Journal (Springer) | March 1st, 2022

Climate change has a pronounced effect on water resources in many semiarid climates, causing populated areas such as San Diego County (USA), to become more vulnerable to

Climate change has a pronounced effect on water resources in many semiarid climates, causing populated areas such as San Diego County (USA), to become more vulnerable to water shortages in the coming decades. To prepare for decreased water supply, San Diego County is adopting policies to decrease water use and to develop additional local sources of water. One new local source of freshwater is produced by a desalination facility that purifies brackish groundwater from the coastal San Diego Formation. This formation has been studied extensively onshore, but little is known about the geology or groundwater quality offshore in the adjacent continental shelf. Because most groundwater systems are interconnected and complex, further analysis is needed to identify offshore geology, possible sequestration of freshwater in the shelf, and potential pathways for saltwater intrusion. This comprehensive understanding is important because seawater intrusion may limit use of the San Diego Formation and longevity of desalination facilities. Controlled-source electromagnetic methods are uniquely suited to detecting offshore groundwater as they are sensitive to changes in pore fluids such as the transition from fresh to brackish groundwater. This paper describes results from surface-towed electromagnetic surveys that mapped the pore-fluid salinity and possible fluid pathways in the continental shelf off the coast of San Diego. The results indicate a considerable volume of fresh-to-brackish groundwater sequestered in the shelf, both in continuous lenses and isolated pockets, that appear influenced by fault systems and shallow stratigraphy.

Identifying American climate change free riders and motivating sustainable behavior

Nature Portfolio (Springer Nature) | March 19th, 2024

Identifying and Addressing Contaminant Sources Impacting an Urban Estuary

San Francisco Estuary Institute (SFEI) | July 1st, 2016

Identifying and Overcoming Barriers to Climate Change Adaptation in San Francisco Bay: Results from Case Studies

California Energy Commission (CEC) | July 31st, 2012

The research goals of this project were threefold: (1) to systematically identify the adaptation barriers encountered by local government entities in San Francisco Bay; (

The research goals of this project were threefold: (1) to systematically identify the adaptation barriers encountered by local government entities in San Francisco Bay; (2) to test empirically the robustness and usefulness of a diagnostic framework (previously developed by the authors) so as to modify or refine its components; and (3) to draw larger lessons about the adaptation process and the importance of adaptation barriers—even in highly developed nations—for the scientific community in terms of future research priorities and for policy-makers. To fulfill these goals, an in-depth study of five California case studies in the San Francisco Bay region (Hayward, San Francisco, Santa Clara and Marin Counties, and the regional adaptation process) was undertaken. Relevant data were collected through key informant interviews, public documents, observation of and/or participation in public meetings, and a statewide survey. The study found growing, but still very limited activities in the case studies. Institutional and attitudinal barriers dominate, but economic barriers are also important, even in wealthy locales. Leadership emerged as a critical factor in moving them forward on adaptation. Science mattered some, but policy and planning opportunities were more significant in motivating or launching the adaptation process. The study also found that communities have assets, aids, and advantages that can help them avoid barriers and that there is significant opportunity to affect and overcome the barriers that are being encountered in the “here and now.” However, local communities need outside intervention to address “legacy” and “remote” barriers. With still very little visible adaptation activity “on the ground,” the study concluded that a big portion of what communities are doing to date is working on overcoming the barriers to adaptation instead.

Identifying Major Hydrologic Change Drivers in a Highly Managed Transboundary Endorheic Basin: Integrating Hydro-ecological Models and Time-Series Data Mining Techniques

American Geophysical Union (AGU) | August 23rd, 2022

The fragile balance of endorheic lakes in highly managed semi-arid basins with transboundary water issues has been altered by the intertwined effects of global warming an

The fragile balance of endorheic lakes in highly managed semi-arid basins with transboundary water issues has been altered by the intertwined effects of global warming and long-term water mismanagement to support agricultural and industrial demand. The alarming rate of global endorheic lakes’ depletion in recent decades necessitates formulating mitigation strategies for ecosystem restoration. However, detecting and quantifying the relative contribution of causal factors (climate variability and anthropogenic stressors) is challenging. This study developed a diagnostic multivariate framework to identify major hydrologic drivers of lake depletion in a highly managed endorheic basin with a complex water distribution system. The framework integrates the Soil and Water Assessment Tool (SWAT) simulations with time-series decomposition and clustering methods to identify the major drivers of change. This diagnostic framework was applied to the Salton Sea Transboundary Basin (SSTB), the host of the world's most impaired inland lake. The results showed signs of depletion across the SSTB since late 1998 with no significant changes in climate conditions. The time-series data mining of the SSTB water balance components indicated that decreases in lake tributary inflows (-16.4 Mm3 yr-2) in response to decline in Colorado River inflows, associated with state water transfer agreements, are causing the Salton Sea to shrink, not changes in the irrigation operation as commonly believed. The developed multivariate detection and attribution framework is useful for identifying major drivers of change in coupled natural-human systems.

Identifying organic contaminants at trespass cannabis grows on federal land in California, USA

Elsevier | September 25th, 2025

Despite the legalization of recreational cannabis in California, USA, illegal cannabis cultivation remains pervasive, partly through the establishment of illegal cult

Despite the legalization of recreational cannabis in California, USA, illegal cannabis cultivation remains pervasive, partly through the establishment of illegal cultivation on public lands (trespass grows). These operations often illegally divert water for irrigation and perform unauthorized applications of chemical fertilizers and pesticides. This work investigates a broad suite of these chemicals, focusing on their persistence in topsoil and presence in water and bed sediment in adjacent streams. Quantitative analyses of pesticides were conducted (183 compounds in water; 176 in topsoil/bed sediment), supplemented by qualitative nontargeted screening at three trespass grows that had no active cultivation for 8 months to 2 years. Targeted multi-residue analysis of topsoil detected the insecticides bifenthrin, cyfluthrin, malathion and imidacloprid (with concentrations up to 38 ng/g dry weight, d.w.), and the fungicides fluopyram, myclobutanil, and triadimefon (concentrations up to 8.1 ng/g d.w.). No pesticides were detected in the companion water or streambed sediment samples from adjacent streams. In addition, no water samples were found to have measurable estrogenic activity. Nontargeted screening uncovered additional pesticides (i.e., spiromesifen, trinexapac) in the topsoil and cannabis-related compounds (i.e., cannabidol, delta9-tetrahydrocannabinol) in both topsoil and streambed sediment suggesting the likelihood of offsite transport of cannabis related compounds. Phthalate plasticizers, rubber-related compounds, pharmaceuticals and personal care product chemicals were detected in topsoil, water, and streambed sediment and may be related to extensive irrigation infrastructure installed at these trespass grows. This work begins to establish a contaminant profile associated with illegal cannabis growing activities, providing a foundation for future research focused on their potential ecological impacts.

Identifying the Amount of Wastewater that is Available and Feasible to Recycle in California

Water Research Foundation (WRF) | July 24th, 2023