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As our population continues to grow, the demand of a more efficient agriculture system heightens. We work to produce the highest yield possible to cover demands. Are we compromising our water quality for mass food production? In past years, the West Coast growers had been facing increasing struggles to farm with their allotted water often turning to groundwater use. California had to adopt measurements to regulate groundwater usage to protect the environment. The East Coast rain on the other hand faces with increasing amounts of algal blooms product of agricultural runoff derived from the consistent amount of rain received in that part of the country. Different approaches are being used to help reduce agricultural runoff like studies maintaining increased microbial activity in the soil to increase phosphorus uptake and preventing it from reaching waterways. California has passed the Sustainable Groundwater Management Act as an effort to encourage more conscious planning of water available.

The author, an instructor of lower division general education (G.E.) geography courses, describes how to incorporate high-impact practices into courses that allow for experiential and project-based learning. Often, these experiences can be framed through a service learning component, which provides students an opportunity to partner with the local community to address regional issues. In this article the author describes a project where students collected water samples from within their own community, which were then analyzed for biological and chemical indicators of water quality. The students subsequently used the results to pose questions within their local community and share knowledge about water management and sustainability.

Innovative education approaches include citizen science projects that allow students to participate in locally relevant scientific work, connecting content to the real world. Global collaboration provides students with a broader perspective on local issues, allowing students to become more globally aware.

Graduate students education is falling short of what the twenty-first century demands from its next generation of leaders; indeed, many educational leaders and scholars have called for graduate education to include richer, more relevant experiences (Stanton & Wagner, 2006; Stewart, 2010; Walker, Jones, Bueschel, & Hutchings, 2008). At the University of California, Davis, we provide a rich set of professional development skills through a new program for graduate students who have an interest in environmentally based public scholarship--researching and collaborating with communities in order to solve real-world challenges. The purpose of this article is to illustrate and analyze the model, identifying ways the program is effectively delivering professional development to graduate students.

A middle school student and teacher watershed education project supports a large wetland restoration effort. It provides community-based, science education for urban, low-income, multicultural 6th-9th grade students and their teachers. This is a bottom-up approach to extending information to the local community about the restoration. The project includes teacher workshops, teacher and student restoration/water quality fieldwork with expert guidance, scientist classroom visits, an essay contest, and research cruise. The project is an example of using place-based, participatory learning toward achieving social-ecological resilience. It is a student education project with broader, community-wide Extension goals.

University of California Sea Grant Extension Program provides training and technical assistance to fishers, farmers, planners, and conservationists on projects such as coastal ecosystem health, marine environmental protection, fisheries management, aquaculture, salmon habitat restoration, and controlling nonpoint-source pollution; supports graduate education in marine-related studies; and funds outdoor marine science camps for children, teachers, and 4-H leaders. (TD)

This article presents a watershed challenge that gives students an opportunity to investigate the challenge of using a watershed area as a site for development, examining the many aspects of this multifaceted problem. This design challenge could work well in a team-based format, with students taking on specific aspects of the challenges and pooling their ideas and research findings. The author describes how to stretch the challenge and consider taking this challenge another step.

Gardening in the American Southwest (SW) is an extreme sport. Not only are gardeners challenged by geographic extremes from tropical deserts to subalpine locales, they must also deal with a wide range of climates. Winter in the mountains and higher regions means heavy snows, frozen soils, and temperatures that can dip below zero. In contrast, summers in the desert can bring weeks where the temperature never gets below 100[degrees] during the day. Most SW public libraries will need a variety of regional gardening titles, including introductory guides to the subject, plant selection books, and resources on landscape design. Additional popular SW gardening topics include drought-resistant horticulture (if there is one consistent challenge throughout the SW, it is water conservation), environmentally responsible landscaping, such as xeriscaping (i.e., not requiring supplemental irrigation), and gardening with native plants. This article presents a list of titles and web resources that are essential for library's SW gardening collection.

Just a few years ago Jefferson Elementary School in San Diego County, California suffered from low test scores and a lackluster "science from workbooks approach" that was not motivating many in the 75% Hispanic and 50% learning-to-speak-English student body. A partnership program with the San Diego Natural History Museum called Communities Alive in Nature (CAN) changed all that. The program centered on using the watershed, where water drains from mountains to the Pacific Ocean, as a broad canvas where teachers and students could investigate local environmental concerns such as water quality, water conservation, native habitats, and erosion. The heart of the program is Adopt a Watershed, a spiral curriculum that builds on students' learning in each successive grade and includes topics such as water quality, soils, plants, animals, and habitats. This article describes how CAN, a museum-school partnership program, turned an underperforming science program into a distinguished one. Positive results are reflected in students' achievement-test scores in science and other subjects. In fact, since the partnership began in 2001, Jefferson's composite scores have risen steadily from 574 to 750. For Hispanic students, the fastest growing segment of the school population, achievement has increased from 492 to 689. (Contains 1 resource.)

Groundwater-resource quality is assumed to be less responsive to drought compared to that of surface water due to relatively long transit times of recharge to drinking-supply wells. Here, we evidence dynamic perturbations in aquifer pressure dynamics during drought and subsequent recovery periods cause dramatic shifts in groundwater quality on a basin scale. We used a novel application of time-series clustering on annual nitrate anomalies at >450 public-supply wells (PSWs) across California's San Joaquin Valley during 2000-22 to group subpopulations of wells with similar water-quality responses to drought. Additionally, we statistically evaluated the direction and magnitude of multi-constituent water-quality changes across the San Joaquin Valley using a broader dataset of >3000 PSWs with data during two select hydrologic stress periods representing an extreme drought (2012-16) and subsequent recovery (2016-19). Results of time-series clustering and stress-period change analyses corroborate a predominant regional response to pumping stress characterized by increased concentrations of anthropogenic constituents (nitrate, total dissolved solids) and decreased concentrations of geogenic constituents (arsenic, fluoride), which largely reversed during recovery. Cluster analysis also identified a secondary, less commonly occurring group of PSWs where nitrate decreased during drought, but explanatory factor analysis was not able to discern hydrogeologic drivers for these two divergent response patterns. Long-term tracer data support the hypothesis that the predominant regional signal of nitrate increase during drought is caused by enhanced capture of modern-aged groundwater by PSWs during periods of pumping stress, which can drive rapid changes in water quality on seasonal and multiannual timescales. Pumping-induced migration of modern, oxic groundwater to depth during drought may affect geochemical conditions in deeper portions of regional aquifers controlling the mobility of geogenic contaminants over the long term. [ABSTRACT FROM AUTHOR]

Multi-year droughts are ever-present and transformational features of California's Mediterranean climate and can fundamentally affect the water quality and the ecosystem responses of the San Francisco Estuary (estuary) and the Sacramento-San Joaquin Delta (Delta). This study assessed data collected by long-term monitoring programs over the past 46 water years (1975-2021) to evaluate how water quality in the estuary changes during multi-year droughts. Data were aggregated by region (South-Central Delta, North Delta, confluence, Suisun Bay, and Suisun Marsh) and season, then differences between multi-year drought periods, multiyear wet periods, and neutral periods were compared using generalized linear models. We found that multi-year drought periods altered multiple physical and chemical parameters in the estuary, increasing water temperature, salinity, water clarity, and nutrient levels. This trend was consistent across regions and seasons, with few exceptions. Increases in these parameters during drought periods were likely caused by reduced Delta inflows that intensified in each successive dry year because of reduced precipitation and managed estuarine inflows and outflows. Drought periods did not substantially affect tidal velocities within the estuary, which remained mostly consistent across wet and drought periods. Trends in chlorophyll concentrations during drought periods were more nuanced with higher concentrations occurring in the South-Central Delta region and during the winter and spring. Together, these results characterized drought in the estuary as warm, clear, high in nutrients, with patchy phytoplankton blooms (as indexed by chlorophyll), all of which have implications for higher trophic levels. Considering that droughts are expected to increase in frequency and intensity in California with climate change, understanding the effects of multi-year droughts on the water quality conditions of the estuary can help inform water management decisions. [ABSTRACT FROM AUTHOR]

Estuaries support ecologically and economically important resources that are vulnerable to ocean acidification from rising anthropogenic CO2. However, complex local processes in estuaries complicate and may disguise long‐term pH trends. For example, terrestrial nutrient runoff and coastal upwelling may exacerbate pH variability and declines. We investigated eutrophication impacts on acidification in a central California estuary, Elkhorn Slough, which receives high nutrient loads from intensive surrounding agriculture and upwelling of the California Current System. We examined drivers of acidification including nutrients, ecosystem metabolism, and upwelling by modeling pH trends over 20 years using a Generalized Additive Mixed Model at four sites from the National Estuarine Research Reserve Systemwide Monitoring Program and collected additional water samples to calculate aragonite saturation. Our models revealed acidification trends over two decades which were more pronounced near the marine inlet. Near the marine inlet, high nutrient levels and lower buffering were associated with the greatest rate of acidification in the estuary, which was four times greater than the trend from anthropogenic CO2 alone. Compared to fully tidal sites, a tidally restricted site showed diminished pH declines over time because of higher mean pH and aragonite saturation levels, but greater diel and seasonal variability associated with cycles of ecosystem metabolism and tidal range. Therefore, short‐term drops of saturation are threats to acidity in this location. The effects of enhanced seasonal cycles or long‐term trends in different zones of the estuary have implications for monitoring estuaries with a temporal frequency and scale to capture coastal acidification risks. Plain Language Summary: Increasing carbon dioxide in the atmosphere also impacts the chemistry of the ocean by lowering pH levels. The water quality indicator pH, a measure of the acidity, is important because pH changes are harmful to marine organisms that are critical for fishery industries. Many of these organisms live in estuary ecosystems, where pH levels are influenced by climate change as well as local conditions including nutrients coming from the ocean and human activities including nutrient pollution. These coastal conditions can worsen pH declines in estuaries. This study examined an estuary in central California, called Elkhorn Slough, that receives nutrient pollution from agriculture as well as nutrients from the ocean. We studied how pH and other signals of acidification have changed over 20 years in this estuary. We found that the change is happening faster here than in the ocean. Also, different locations in the estuary showed distinctive patterns of acidification. The site near the marine inlet changed faster over time, but others sites showed more variation between different seasons of the year. These results depended on the sampling location in the estuary, and therefore it is important that ongoing measurements of the pH capture multiple sites within estuaries. Key Points: Metabolism of high nutrient loads in Elkhorn Slough, CA, enhances trends of coastal acidification compared to open ocean acidificationHigh nutrient levels and lower buffering drive the greatest rate of acidification over two decades near the marine inlet of the estuaryTemporal cycles of ecosystem metabolism and tides are threats to acidification in a tidally restricted site [ABSTRACT FROM AUTHOR]

Wildfires are a worldwide disturbance with unclear implications for stream water quality. We examined stream water chemistry responses immediately (<1 month) following a wildfire by measuring over 40 constituents in four gauged coastal watersheds that burned at low to moderate severity. Three of the four watersheds also had pre‐fire concentration‐discharge data for 14 constituents: suspended sediment (SSfine), dissolved organic and inorganic carbon (DOC, DIC), specific UV absorbance (SUVA), major ions (Ca2+, K+, Mg2+, Na+, Cl−, SO42− ${{\text{SO}}_{4}}^{2-}$, NO3− ${{\text{NO}}_{3}}^{-}$, F−), and select trace elements (total dissolved Mn, Fe). In all watersheds, post‐fire stream water concentrations of SSfine, DOC, Ca2+, Cl−, and NO3− ${{\text{NO}}_{3}}^{-}$ changed when compared to pre‐fire data. Post‐fire changes in SO42− ${{\text{SO}}_{4}}^{2-}$, K+, Na+, Mg2+, DIC, SUVA, and total dissolved Fe were also found for at least two of the three streams. For constituents with detectable responses to wildfire, post‐fire changes in the slopes of concentration‐discharge relationships commonly resulted in stronger enrichment trends or weaker dilution trends, suggesting that new contributing sources were surficial or near the surface. However, a few geogenic solutes, Ca2+, Mg2+, and DIC, displayed stronger dilution trends at nearly all sites post‐fire. Moreover, fire‐induced constituent concentration changes were highly discharge and site‐dependent. These similarities and differences in across‐site stream water chemistry responses to wildfire emphasize the need for a deeper understanding of landscape‐scale changes to solute sources and pathways. Our findings also highlight the importance of being explicit about reference points for both stream discharge and pre‐fire stream water chemistry in post‐fire assessment of concentration changes. Plain Language Summary: Wildfires are becoming more common, yet the effects of wildfire on streams and their water quality remain unclear. Changes in stream water quality following a wildfire can have consequences for drinking water and aquatic ecosystems. We studied how stream water quality changed in four impacted watersheds following the 2020 CZU Lightning Complex Wildfire in central coastal California using measurements of stream water chemistry coupled with analysis of burned soils and ash from the same area. For sites with pre‐fire data, we found that wildfire impacts on stream water quality were greatest in the most extensively burned watershed. We also found that stream water quality changes were distinct across watersheds and dependent on stream discharge. Chemical measurements of potential sources of solutes, like ash and burned soils, indicate that the variability in stream water quality was consistent with contributions from ash or other burned landscape materials. The location, composition, and amount of these wildfire‐generated sources vary in space and time. This complexity can lead to some similarities as well as differences in water quality responses of different streams, like those found in our study. Key Points: Post‐fire stream water chemistry impacts were usually site, constituent, and discharge‐dependent, reflecting dynamic fire‐induced changesDespite this variability, slopes of concentration‐discharge relationships often became more positive post‐fire, implying altered surface or near‐surface sourcesHeterogeneity in fire‐generated sources and processes contributes to complexities in post‐fire stream water chemistry [ABSTRACT FROM AUTHOR]

The Salton Sea is the largest lake in California and is a shallow, hypersaline lake. The endorheic lake has been significantly maintained by agricultural return flows from Imperial Valley farming and two rivers- the New River and Alamo River- which originate in Mexicali, Mexico. The current salinity is at 74 ppt and is expected to increase due to the Quantification Settlement Agreement signed in 2003, stipulating the transfer of nearly 0.616 km³ per year of Colorado River water to urban areas for up to 75 years. This has resulted in inflows reduction, and the dust storms created by the dried-up playa have become a prominent risk to public health in the region. Massive fish and bird kills began in the 1980s and continued to occur periodically. In this study, the Delft3D numerical modeling suite- FLOW, WAVE, and WAQ- was utilized to investigate the transport and cycling of nutrients under the influence of wind-induced sediment resuspension activity. The three-dimensional hydrodynamic and water quality combined model was applied to simulate mitigation scenarios to assess long-term effects on salinity and water quality of (1) emerged islands as a nature-based solution, (2) seawater import/export, and (3) seawater import/export in addition to treating tributary rivers to remove nutrients. Overall, this study supported the findings fromprevious studies and showed that sediment resuspension is the driving force for nutrients cycling in the water column and that emerged islands have long-term potential to enhance burial activity for pollutants removal in the Salton Sea. Furthermore, the seawater import/export scenario showed promising results of reducing salinity level from 46 ppt to 38-39 ppt in 2 years. The 3D numerical hydrodynamic/water quality model developed in this work is the first and latest integrated modeling approach tailored to the Salton Sea's system and has the capacity to improve understanding of the complicated water quality dynamics changes in various restoration concepts. This study demonstrated that being able to explore the full potentials of restoration designs using a comprehensive 3D water quality modeling framework is critical in achieving wholesome planning that will create environmental, social, and economic benefits in the long term for the Salton Sea. [ABSTRACT FROM AUTHOR]

In order to realize the accurate and reliable prediction of the change trend of dissolved oxygen (DO) content in California perch aquaculture water, this paper proposes a second-order hybrid optimization support vector machine (SVR) model based on Differential Evolution (DE) and Gray Wolf Optimizer (GWO), shortened to DE-GWO-SVR, to predict the DO content with the characteristics of nonlinear and non-smooth water quality data. Experimentally, data for the water quality, including pH, water temperature, conductivity, salinity, total dissolved solids, and DO, were collected. Pearson's correlation coefficient (PPMCC) was applied to explore the correlation between each water quality parameter and DO content. The optimal DE-GWO-SVR model was established and compared with models based on SVR, back-propagation neural network (BPNN), and their optimization models. The results show that the DE-GWO-SVR model proposed in this paper can effectively realize the nonlinear prediction and global optimization performance. Its R2, MSE, MAE and RMSE can be up to 0.94, 0.108, 0.2629, and 0.3293, respectively, which is better than those of other models. This research provides guidance for the efficient prediction of DO in perch aquaculture water bodies for increasing the aquaculture effectiveness and reducing the aquaculture risk, providing a new exploratory path for water quality monitoring. [ABSTRACT FROM AUTHOR]

Water reuse with Advanced Water Treatment (AWT) is increasingly appealing for urban areas seeking water supply reliability. In cities facing water scarcity, how can large-scale reuse support reliability and how do reuse operations affect water quality, energy use, and water conservation? This paper presents a systems analysis of metropolitan-scale water reuse and its effects on water supply and quality. For the case study of Los Angeles County, California, USA, hydroeconomic modeling is used to evaluate reuse as a contributor to water supply given urban water conservation, drought-induced water scarcity, and costs and benefits for supply and demand. Results indicate that AWT can be a viable source of supply especially when coupled with conservation. Across modeled scenarios, reuse provides as much as 30% of regional supplies. New water reuse with AWT becomes viable when imported water availability is 50% or less of historic values. Existing indirect potable reuse operations in the county remain important. Systemwide energy intensity of operations increases with greater reuse in the absence of water conservation. Modeled influent flow rates to wastewater treatment plants resemble historical values, but extreme flow events could pose risks. The paper offers a holistic framework to evaluate water reuse as a component of urban water management. [ABSTRACT FROM AUTHOR]

A bench-scale dose-response study evaluated the efficacy of a commercially available copper-based molluscicide known as EarthTec QZ for controlling quagga veligers collected from three Southern California sites impacted by quagga mussels. A variety of concentrations were tested (0, 3, 16.7, 33.4, and 50.1 µL/L of EarthTec QZ or 0, 0.18, 1.0, 2.0, 3.0 mg/L as copper (Cu), respectively) for different durations (0.5, 2, 5, and 24 hours) on quagga mussel veligers. Water from each study site was also used in non-target 96-hour acute toxicity testing of three other species. A suite of water quality parameters was measured to characterize the differences between the study sites. The federal and California secondary maximum contaminant level and action level for copper in drinking water are 1.0 and 1.3 mg/L as Cu, respectively; therefore, results for the 16.7 µL/L EarthTec QZ (1.0 mg/L as Cu) test condition were the main reference point for assessing the efficacy of EarthTec QZ as a feasible treatment strategy. Under this condition, veliger mortality at two study sites, Lake Mathews, and a downstream water treatment plant, was found to be greater than 60% and 85% after 5 hours, and 95% and 100% after 24 hours, respectively. Lower efficacy was observed for the Lake Piru study site, with approximately 30% veliger mortality after 24 hours. Alkalinity, dissolved organic carbon, and chemical oxygen demand were found to be significant variables for veliger mortality in these hard water locations based on linear regression modeling. The three non-target indicator species were adversely affected by EarthTec QZ at concentrations tested. These results indicate that this product has potential as an effective chemical control agent against quagga veligers at low doses, but the aforementioned water quality parameters must be considered with full-scale application to optimize target efficacy, while minimizing exposure to non-target species and costs. [ABSTRACT FROM AUTHOR]

This paper describes a public domain semiautomated data screening and quality assurance processing tool useful for both discrete and continuous data. This application serves both a field research project assessing salinity and methylmercury drainage load control options and the requirements of a public domain watershed-based water quality forecasting model used to provide decision support for short-term salinity management in the San Joaquin River Basin of California. The US Army Corps of Engineers HEC-DSSVue data management and visualization platform was enhanced in the former application with Python scripts that performed the basic data quality assurance functions. Analogous tools were developed for use on the HOSTGATOR cloud server using the same Python scripts and algorithms to migrate quality-controlled data directly to a server for use by the Watershed Analysis Risk Management Framework (WARMF) water quality forecasting model. The Python scripts for both applications are easily adaptable by other potential users who do not currently have the resources to implement an enterprise-level hydrological data management and real-time quality assurance software system. [ABSTRACT FROM AUTHOR]

Salt marshes remove terrestrially derived nutrients en route to coasts. While these systems play a critical role in improving water quality, we still have a limited understanding of the spatiotemporal variability of biogeochemically reactive solutes and processes within salt marshes. We implemented a high‐frequency sampling system to monitor sub‐hourly nitrate (NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$) concentrations in salt marsh porewater at Elkhorn Slough in central California, USA. We instrumented three marsh positions along an elevation gradient subjected to different amounts of tidal inundation, which we predicted would lead to varied biogeochemical characteristics and hydrological interactions. At each marsh position, we continuously monitored porewater NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$ concentrations at depths of 10, 30, and 50 cm and porewater levels measured at 70 cm depth over seven deployments of ~10 days each that spanned seasonal wet/dry periods common to Mediterranean climates. We quantified tidal event hysteresis between NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$ and water level to understand how NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$ concentrations and sources fluctuate across tidal cycles. In dry periods, the NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$‐porewater level relationship indicated that the NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$ source was likely estuarine surface water that flooded the transect during high tides and the salt marsh was a NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$ sink. In wet periods, the NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$‐porewater level relationship suggested the salt marsh was a source of NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$. These findings suggest that tidal and seasonal hydrologic fluxes together control NO3−$$ \mathrm{N}{\mathrm{O}}_3^{-} $$ porewater dynamics and export and influence ecological processes in coastal environments. [ABSTRACT FROM AUTHOR]

Low liquid limit clay has a low plastic index, displays poor strength, and is sensitive to water, and its mechanical qualities decline as the water content changes, making it difficult to employ directly in the construction process. Adding lime is a fantastic way to improve it. The influence of lime concentration on the road performance of low liquid limit clay is investigated in this research using a limit water content test, compaction test, and California bearing ratio test. The results show that the original plain soil does not meet the requirements of highway subgrade filling, and the basic properties of subgrade soil are improved to varying degrees after adding lime, resolving the problem regarding the original well-cultivated soil's inability to meet the requirements of construction. The plastic limit of the improved soil increased by roughly 3% as the lime content increased, but the maximum dry density decreased dramatically by 9.03%, 5.71%, and 5.98%, respectively. With an increase of 57.3% in lime content and compaction times, the California bearing ratio increases dramatically. The ideal moisture content rises as the lime content rises. The optimal dosage is 6%, according to a rigorous study of several performance metrics. [ABSTRACT FROM AUTHOR]

Fecal indicator bacteria (FIB) are monitored at beaches to assess water quality and associated health risk from recreational exposure. However, monitoring is generally conducted infrequently (i.e. weekly or less often), potentially leading to inaccurate assessment of water quality at a beach at the time of use. While some work has shown that FIB in marine environments can vary over short (e.g. subhourly) time scales, that work has been mainly focused on 'open' beaches. 'Enclosed' beaches—those that are partially barriered from exchange with offshore water and thus have different residence times and mixing dynamics in the nearshore environment—have been less studied. Here we present results from a high-frequency (once per 30 minutes) FIB sampling event conducted within a Central California, USA, harbor over 48 hours. FIB concentrations at this enclosed site were more variable at high-frequencies than what has been reported at open beach sites. Correlation and regression analyses showed FIB concentrations were most strongly associated with chlorophyll a concentration, turbidity, wind speed, and tide level. Results indicate the importance of measuring FIB concentrations and explanatory environmental parameters at appropriate temporal resolutions when conducting water quality monitoring or source tracking studies. Overall, this work highlights how high-frequency sampling can effectively provide information about water quality dynamics at beaches of interest. [ABSTRACT FROM AUTHOR]

People in coastal cities around the world harvest seafood from local bays despite well-documented health risks. In cities such as San Diego, California, USA, much information about contaminants and human consumption patterns exists for finfish but is largely lacking for shellfish. This study sought to better understand shellfish contamination risks and human vulnerability to inform management and advisories. In summer 2018 and winter 2019, we sampled crustaceans for chemical contaminants and anthropogenic debris and throughout the year surveyed people harvesting from three public fishing piers around San Diego Bay. Of the emerging contaminants found, pyrethroids, benzylbutyl phthalate, PFOS and anthropogenic debris were in differing concentrations in the muscle and viscera of the California spiny lobster and two species of crabs. Combined with previous metal and organic contaminant data from the lobster, 22 contaminants were detected with 5 exceeding consumption thresholds and 8 lacking defined thresholds. California spiny lobster was the main crustacean harvested from piers, attracting shellfishers from a range of ages, incomes, home locations and self-identified racial/ethnic groups. Consumption preferences (e.g., muscle or viscera) were non-discriminant, making lobster contamination a community-wide risk. More monitoring of emerging contaminants and different shellfish species (and tissues) of interest is recommended to capture the spatial and temporal dynamics of health risks, especially because the use of bivalves as sentinels may not reveal the same risks (e.g., PFAS, phosphate flame retardants). [ABSTRACT FROM AUTHOR]

Regional, national, and international 30 × 30 conservation initiatives would be strengthened by including a specific focus on freshwater ecosystem conservation that supplements terrestrial conservation strategies. Globally, freshwater habitats support essential biodiversity and ecosystem services, yet are being lost at disproportionately high rates relative to terrestrial systems. Making freshwater ecosystems an explicit focus of 30 × 30 initiatives would assist in curtailing these losses while advancing 30 × 30's mission to address climate change, economic sustainability, food security, and equitable outdoor access across a variety of landscapes. Here, we explain how fresh water can serve as a key piece of 30 × 30 conservation efforts. We emphasize that to address the challenges of traditional area‐based conservation programs, 30 × 30 should (1) focus on watershed‐scale conservation planning and (2) evaluate conserved areas based on five freshwater priorities: connectivity, watershed disturbance, flow alteration, water quality, and biodiversity. We use examples from the US state of California to illustrate how addressing freshwater systems can help guide 30 × 30 conservation. [ABSTRACT FROM AUTHOR]

Introduction: The impact of water quality on the survival of human norovirus (NoV) was determined in irrigation water field run-off (tail water) and well water from a representative Central Coast vegetable production site in the Salinas Valley, California. Methods: Tail water, well water, and ultrapure water samples were inoculated separately with two surrogate viruses for human NoV--Tulane virus (TV) and murine norovirus (MNV)--to achieve a titer of 1×105 plaque forming units (PFU)/ml. Samples were stored at 11, 19, and 24°C for 28 days. Additionally, inoculated water was applied to soil collected from a vegetable production site in the Salinas Valley or to the surface of growing romaine lettuce leaves, and virus infectivity was evaluated for 28 days in a growth chamber. Results: Virus survivalwas similar for water stored at 11, 19, and 24°C and there was no difference in infectivity based on water quality. After 28 days, a maximum1.5 log reduction was observed for both TV and MNV. TV decreased by 1.97-2.26 log and MNV decreased by 1.28-1.48 logs after 28 days in soil; infectivitywas not influenced bywater type. Infectious TV and MNV were recovered from lettuce surfaces for upto 7 and 10 days after inoculation, respectively. Across the experiments there was no significant impact of water quality on the stability of the human NoV surrogates. Discussion: Overall, the human NoV surrogates were highly stable in water with a less than 1.5 log reduction over 28 days and no difference observed based on the water quality. In soil, the titer of TV declined by approximately 2 logs over 28 days, while MNV declined by 1 log during the same time interval, suggesting surrogatespecific inactivation dynamics in the soil tested in this study. A 5-log reduction in MNV (day 10 post inoculation) and TV (day 14 post inoculation) was observed on lettuce leaves, and the inactivation kinetics were not significantly impacted by the quality of water used. These results suggest that human NoV would be highly stable in water, and the quality of the water (e.g., nutrient content, salinity, and turbidity) does not significantly impact viral infectivity. [ABSTRACT FROM AUTHOR]

Urban waterways degradation due to runoff from residential areas can be reduced by adopting best management practices (BMPs) for irrigation, fertilizer, and pesticide use. Although stormwater runoff from urban areas has been studied extensively, we focus on single-family residential land use specifically. Outreach to individual households may have a measurable impact since decisions are being made here. We surveyed households to evaluate the effectiveness of education and outreach campaigns on self-reported use of water and chemicals and evaluated whether self-reported behaviors were reflected in the quality and quantity of water draining from the study areas before and after outreach efforts. Our research was conducted in California, which has a Mediterranean climate with distinct wet and dry periods. Runoff from residential landscapes during the dry season enters waterways undiluted by rainwater, making this runoff particularly detrimental to receiving waters. No significant differences in behavior and BMP adoption from before and after the education and outreach campaign was found. These results are not atypical and may be explained by several factors including the population approach to the survey, lag times between outreach and measurable effects, and the need for a critical threshold of adoption to be met for effects to be measurable. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To examine students' experiences of water security at school and how experiences relate to intake of water from different sources of water at school. DESIGN/METHODS: In this cross-sectional study, 651 students in grades 3 to 5 in 12 low-income public elementary schools in the San Francisco area completed surveys about their daily intake of water from different sources of water at school, experiences of water security including safety, cleanliness, and taste of water at school, and their demographics. Multivariable linear regressions examined associations between students' water security experiences at school and reported intake from different sources of water at school. RESULTS: Approximately half of students were Latino (56.1%) and had overweight/obesity (50.4%). Most (74.5%) had some negative water security experience at school. Students drank from the school fountain or water bottle filling station a mean of 1.2 times/day (standard deviation [SD] = 1.4), sinks 0.2 times/day (SD = 0.7), tap water dispensers 0.2 times/day (SD = 0.6), and bottled water 0.5 times/day (SD = 1.0). In multivariable linear regression, students with more negative experiences of school water security drank less frequently from fountains (-0.5 times/day, P value < .001), but more frequently from tap water dispensers (0.1 times/day, P value = .040) and sinks (0.1 times/day, P value = .043), com- pared to students with no negative perceptions. CONCLUSIONS: On average, students had negative school water security experiences, which decreased their consumption of water from tap water sources. However, relationships between negative water security experiences and reported water intake appeared to be mitigated by water source. Schools should consider installing more appealing water sources to promote water intake. [ABSTRACT FROM AUTHOR]

Clear Lake (Lake County, CA, USA) is hypereutrophic and used for drinking water, tribal use, and supports a significant fishing economy. The Mendocino Complex (2018), one of the largest wildfires in California's post‐settlement history, burned 40% of the Clear Lake watershed, providing a timely opportunity to study the impacts of historical and current wildfires on this valuable aquatic resource. Using long‐term monthly monitoring data from 1968 to 2019, paired with historical watershed fire data, we found that for the three largest fire years in the watershed's history, 3‐year postfire median July–October epilimnetic total phosphorus (TP) concentrations were below or equal to 3‐year prefire TP concentrations. However, both median TP epilimnetic concentrations and deepwater temperature across the lake have increased since the late 1960s. Long‐term TP increases were more strongly correlated with monthly maximum air temperatures than precipitation, suggesting a potential role of warming‐induced water column stratification, dissolved oxygen (DO) depletion, and high potential for internal phosphorus loading. Hypoxic occurrences were correlated with higher hypolimnetic soluble reactive phosphorus and TP concentrations, but additional high‐frequency monitoring of DO will help determine the duration of anoxia and its contribution to internal phosphorus loading. These long‐term data suggest that for this large, hypereutrophic lake, wildfires did not significantly alter in‐lake TP concentrations based on long‐term, monthly monitoring and that other internal or external sources of TP may mask any wildfire effects. Nonetheless, our study underscores the value of synthesizing decades of water quality, watershed wildfire, and climate data to build a more comprehensive, nuanced picture of multiple long‐term threats to aquatic ecosystems under global change. Moreover, monitoring and studying fire effects across a wide range of lake types beyond this study will help promote more effective lake management during changing climates and increasingly frequent large wildfires. [ABSTRACT FROM AUTHOR]

We examined conditions that form or prevent thermal stratification in river pools using field measurements, statistical modelling, and three‐dimensional (3D) computational fluid dynamics (CFD) modelling. Our motivation is to identify variables that control stratification for exploitation to enhance or prevent thermal gradients as needed to benefit species in rivers. One study pool (UT) is located above water storage reservoirs and receives natural flows, and the other pool (PT) is regulated and receives unnaturally high, cold water in summer; both pools are on the Trinity River, California. Thermal stratification formed in UT pool in spring at a critical flow of 1.01 m3/s, peaked at 8.1°C in summer, and exhibited diurnal formation and destruction under sub‐critical flows until fall. At PT pool, the 14.2 m3/s baseflow caused mixing that prevented stratification and formed a spatially homogenous thermal environment. Statistical analyses indicated the daily range in air and inlet water temperature at UT pool best correlated with the occurrence and strength of stratification but were progressively irrelevant as flows increased above the critical value. The validated CFD model was used to reproduce the diurnal stratification and explain the processes involved. The CFD model correctly predicted the observed critical flow and replicated the dynamics of stratification at UT pool and isohyets observed at PT pool. The CFD results also confirmed that low flows are the main variable for stratification to form, and the daily range in inlet water temperature drives the strength of the thermal gradient. The model estimated a critical discharge at PT pool of 2.0 m3/s, twice that for UT pool owing to its 2.6‐times larger area, suggesting critical flows scale with pool size. Results showed that releasing critical and lower flows in summer on regulated streams may conserve water and provide thermal gradients that benefit poikilothermic species; alternately, higher than critical flows can prevent stratification where needed to improve water quality. [ABSTRACT FROM AUTHOR]

In California (USA), seasonal lagoons provide important oversummer rearing habitat for juvenile steelhead trout (anadromous Oncorhynchus mykiss). However, key water quality parameters such as temperature and dissolved oxygen concentration can periodically approach or exceed the physiological tolerances of steelhead during the protracted dry season. A field study employing distributed temperature sensing technology, water quality monitoring, habitat mapping, and mark-recapture sampling was conducted to examine how shifting environmental conditions affected the performance and behavior of juvenile steelhead in the Scott Creek estuary/lagoon (Santa Cruz County). Abiotic conditions were driven by episodic inputs of seawater to the typically freshwater lagoon. During midsummer, the water column was vertically stratified which reduced suitable lagoon rearing habitat by approximately 40%. Nevertheless, steelhead abundance, growth, and condition factor were high during the summer and decreased in autumn following lagoon destratification and cooling. Unlike previous work, this study identified limited emigration from the lagoon to riverine habitat during the summer. Instead, juvenile steelhead exhibited crepuscular movement patterns within the lagoon, with peaks in upstream (to upper lagoon habitat) and downstream (to lower lagoon habitat) movement occurring at dawn and dusk, respectively. This study underscores that habitat complexity and connectivity are critical for juvenile steelhead production and persistence and provides insight into steelhead habitat use and behavior in seasonal lagoons. [ABSTRACT FROM AUTHOR]

The potential for machine learning to answer questions of environmental science, monitoring, and regulatory enforcement is evident, but there is cause for concern regarding potential embedded bias: algorithms can codify discrimination and exacerbate systematic gaps. This paper, organized into two halves, underscores the importance of vetting algorithms for bias when used for questions of environmental science and justice. In the first half, we present a case study of using machine learning for environmental justice-motivated research: prediction of drinking water quality. While performance varied across models and contaminants, some performed well. Multiple models had overall accuracy rates at or above 90 % and F2 scores above 0.60 on their respective test sets. In the second half, we dissect this algorithmic approach to examine how modeling decisions affect modeling outcomes - and not only how these decisions change whether the model is correct or incorrect, but for whom. We find that multiple decision points in the modeling process can lead to different predictive outcomes. More importantly, we find that these choices can result in significant differences in demographic characteristics of false negatives. We conclude by proposing a set of practices for researchers and policy makers to follow (and improve upon) when applying machine learning to questions of environmental science, management, and justice., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Cyanobacteria harmful algal blooms (CHABs) became a concern in the upper San Francisco Estuary, California beginning in 1999, when yearly blooms of Microcystis began in the Delta region. Subsequent research identified that the increase in the magnitude, duration and toxicity of Microcystis blooms was associated with drought related conditions of elevated water temperature and low streamflow. However, the impact of extreme conditions on the resilience of the bloom was unknown. The 2014 and 2017 water years provided a unique opportunity to determine the effect of climatic "whiplash" produced by the occurrence of extreme wet conditions following extreme dry conditions on the Microcystis bloom. We hypothesized that the period of record wet conditions in 2017 (1906-2018) would eliminate the Microcystis bloom for that year and perhaps revert the estuary phytoplankton community back to pre-bloom conditions due to extreme flushing, despite the increase in magnitude and spatial and temporal distribution of the Microcystis bloom during the 2014 extreme dry year. Field sampling was conducted at 2-week or 4-week intervals between July and November at stations throughout the Delta for both years and included a suite of physical, chemical and biological factors. Using PRIMER-e DISTLM, we determined that retention time in the upper estuary and water temperature were key environmental correlates with the Microcystis bloom amplitude and in regression models described 58-78% of the variation of the bloom surface biovolume or subsurface abundance. The period of record high streamflow in 2017 was not enough to eliminate the Microcystis bloom. However, the bloom was small in 2017, with a low abundance, late initiation, short duration, narrow distribution and low toxin production. Warm water temperature enabled the bloom to flower in late summer despite streamflow many times those measured previously. In addition, although conditions early in the summer of 2017 favored diatoms, the summer was characterized by an abundance of other non- Microcystis cyanobacteria. We conclude that once established, Microcystis is likely to be resistant to extreme wet conditions, as long as water temperature and other key water quality conditions are favorable. •Demonstrated the impact of rapid climate shift on harmful algal blooms. • Demonstrated the importance of water temperature in facilitating resilience of harmful algal blooms, despite record precipitation events. [ABSTRACT FROM AUTHOR]

Several classes of pesticides have been shown to impair water quality in California, including organophosphates, pyrethroids and neonicotinoids. Vegetative treatment systems (VTS) can reduce pesticide loads and associated toxicity in agricultural runoff, but many water-soluble pesticides such as neonicotinoids are not effectively treated by VTS, and VTS installation is not always an option for growers required to remove non-crop vegetation for food safety concerns. Recent studies have shown that biochar filtration can be used to remove soluble contaminants, especially when coupled with other VTS components. We evaluated a mobile carbon filter system consisting of a trailer-mounted tank containing approximately 600L (~ 180 kg) of biochar. Input water from a 437-hectare agricultural drainage was pre-filtered and treated with biochar during two multi-week study periods. Laboratory toxicity tests and chemical and nutrient analyses were conducted on input and output water. Pesticide concentrations were initially reduced by greater than 99%. Treatment efficacy declined linearly and was expected to remain at least 50% effective for up to 34 weeks. Toxicity was assessed with Ceriodaphnia dubia, Hyalella azteca and Chironomus dilutus. Significant input toxicity was reduced to non-toxic levels in 6 of 16 samples. Some input concentrations of the neonicotinoid imidacloprid and the pyrethroid cypermethrin exceeded organism-specific toxicity thresholds and benchmarks, but the overall causes of toxicity were complex mixtures of agricultural chemicals. Nutrients were not reduced by the biochar. Results demonstrate the utility of biochar in treating agricultural runoff and provide measures of the longevity of biochar under field conditions. [ABSTRACT FROM AUTHOR]

Understanding reproductive biology and performance of fish is essential to formulate effective conservation and management programs. Here, we studied reproductive strategies of female Delta Smelt Hypomesus transpacificus, an endangered fish species in the State of California, the United States, focusing on (1) better understanding their distribution pattern during the winter and spring spawning season at very fine scale to predict their possible spawning grounds and (2) assessing impacts of a recent, severe drought on their reproductive performance. We formulated our hypotheses as follows; (1) female Delta Smelt migrate to particular locations for spawning so that mature females can be frequently found in those locations throughout the spawning season and (2) reproductive performance of individual female fish declined during the drought. To test the first hypotheses, we analyzed relationships between water quality parameters and maturity/distribution pattern of Delta Smelt. Salinity better explained the distribution pattern of Delta Smelt at subadult and adult stages compared with water temperature or turbidity. Although there are some freshwater locations where mature Delta Smelt can frequently be found during the spawning season, Delta Smelt at the final maturation stage (Stage 5: hydration) and post spawners appeared to be widespread in the area where salinity was below 1.0 during the spawning season. Therefore, Delta Smelt could theoretically spawn in any freshwater locations, with more specific spawning requirements in the wild (e.g., substrate type and depth) still unknown. Delta Smelt, which experienced dry and critically dry conditions (the 2013 and 2014 year-classes), showed smaller oocytes, and lower clutch size and gonadosomatic index compared with the fish caught in a wet year (2011 year-class) at the late vitellogenic stage (Stage 4 Late), suggesting reproductive performance was negatively affected by environmental conditions during the drought. [ABSTRACT FROM AUTHOR]

Condition indices are key predictors of health and fitness in wild fish populations. Variation in body condition, therefore, can be used to identify stressful conditions that may impact endangered species, such as California's endemic Delta Smelt (Hypomesus transpacificus McAllister, 1963). Here, we examined spatiotemporal variation in the condition indices of > 1600 Delta Smelt collected over nine years (2011–2019), a period characterized by tremendous variability in hydrodynamic and water quality conditions. The population exhibited low hepatosomatic index (HSI) and condition factor (CF) during September/October/November (fall), and both condition indices declined over the nine-year study during fall. HSI was positively correlated with indicators of pelagic productivity (e.g., Chlorophyll a, zooplankton biomass, and proximity to tidal wetlands), whereas CF was negatively correlated with temperature, peaking at a relatively cool 10–13 °C. In sum, seasonal and interannual variation in body condition corresponded most strongly with pelagic productivity and water temperature, with little correlation to freshwater outflow. Management actions that increase pelagic productivity, restore and freshen productive wetlands during late summer-fall, and reduce water temperatures overall are likely to benefit condition indices and, therefore, fitness of the Delta Smelt population. [ABSTRACT FROM AUTHOR]

The global decline of marine foundation species (kelp forests, mangroves, salt marshes, and seagrasses) has contributed to the degradation of the coastal zone and threatens the loss of critical ecosystem services and functions. Restoration of marine foundation species has had variable success, especially for seagrasses, where a majority of restoration efforts have failed. While most seagrass restorations track structural attributes over time, rarely do restorations assess the suite of ecological functions that may be affected by restoration. Here we report on the results of two small‐scale experimental seagrass restoration efforts in a central California estuary where we transplanted 117 0.25‐m2 plots (2,340 shoots) of the seagrass species Zostera marina. We quantified restoration success relative to persistent reference beds, and in comparison to unrestored, unvegetated areas. Within three years, our restored plots expanded ~8,500%, from a total initial area of 29 to 2,513 m2. The restored beds rapidly began to resemble the reference beds in (1) seagrass structural attributes (canopy height, shoot density, biomass), (2) ecological functions (macrofaunal species richness and abundance, epifaunal species richness, nursery function), and (3) biogeochemical functions (modulation of water quality). We also developed a multifunctionality index to assess cumulative functional performance, which revealed restored plots are intermediate between reference and unvegetated habitats, illustrating how rapidly multiple functions recovered over a short time period. Our comprehensive study is one of few published studies to quantify how seagrass restoration can enhance both biological and biogeochemical functions. Our study serves as a model for quantifying ecosystem services associated with the restoration of a foundation species and demonstrates the potential for rapid functional recovery that can be achieved through targeted restoration of fast‐growing foundation species under suitable conditions. [ABSTRACT FROM AUTHOR]

Very few studies have been undertaken on water quality from mobile homes, with most information coming from press and policy reports suggesting that people living in mobile homes in the US have poor water quality. Our goal was to evaluate resident exposure to microbes at the point of use of tap water sourced from the Oasis Mobile Homes Park (OMHP), using physico-chemical parameters, concentrations of target cultivatable microbes, and quantitative polymerase chain reaction (qPCR) analyses. In this study, we sampled 15 mobile homes (MHs) and found arsenic concentrations to be 4-8 times above the acceptable EPA standard of 10 ppm. Our qPCR demonstrated high concentrations of gene targets for Salmonella spp., L. monocytogenes, P. aeruginosa, C. jejuni, E. faecalis, and E. coli in one or more of our sampled mobile homes. Except for MH4, which had the highest concentration of L. monocytogenes and E. faecalis, all MHs had different predominant microorganisms. Based on the physico-chemical parameters and our microbiological analysis, we conclude that drinking water from MH taps in the OMHP is unsafe for consumption. [ABSTRACT FROM AUTHOR]

Drought‐induced pumpage has precipitated dramatic groundwater‐level declines in California's Central Valley over the past 30 yr, but the impacts of aquifer overdraft on water quality are poorly understood. This study coupled over 160,000 measurements of nitrate from ∼6,000 public‐supply wells with a 30 yr reconstruction of groundwater levels throughout the Central Valley to evaluate dynamic relations between aquifer exploitation and resource quality. We find that long‐term rates of groundwater‐level decline and water‐quality degradation in critically overdrafted basins accelerate by respective factors of 2–3 and 3–5 during drought, followed by brief reversals during wetter periods. Episodic water‐quality degradation can occur during drought where increased pumpage draws shallow, contaminated groundwater down to depth zones tapped by long‐screened production wells. These data show, for the first time, a direct linkage between climate‐mediated aquifer pumpage and groundwater quality on a regional scale. Plain Language Summary: It has been established that wells are at risk to run dry when groundwater levels decline during drought, but associated impacts to water quality are poorly understood. This study examined 30 yr of data from California's Central Valley to find dramatic groundwater‐level declines during drought were associated with worsening groundwater quality. This likely happens because increased pumping during drought can draw shallow, contaminated groundwater to depths commonly tapped by public drinking‐water wells. This is the first study of its kind to show direct linkages between drought and groundwater quality at such a broad spatial scale. Key Points: Drought‐induced pumpage has precipitated dramatic groundwater‐level declines in California's Central Valley over the past 30 yrLong‐term rates of groundwater‐level decline and water‐quality degradation in overdrafted basins accelerate by factors of 2–5 during droughtIncreased pumpage during drought can draw shallow, contaminated groundwater down to depths tapped by long‐screened production wells [ABSTRACT FROM AUTHOR]