Valley Of California Research Articles

Unanswered questions from abortion seekers: An application of the Research Prioritization by the Affected Community (RPAC) protocol in the Central Valley, California.

Despite protections offered in California, there is limited understanding of abortion access in underserved regions, including the Central Valley. Furthermore, there has been limited community involvement, especially from those directly affected, in the development of research priorities in abortion care. We utilized the Research Prioritization of Affected Communitiesprotocol to identify research priority topics and research questions for future abortion-related research. This project was designed and implemented through a partnership between a community-based reproductive justice organization and academic and community researchers. We recruited individuals ≥18 years old, English or Spanish speaking, who previously accessed abortion care in Central California. Over two Research Prioritization of Affected Communities sessions, participants shared uncertainties about the abortion care they received (session 1) and ranked their unanswered questions (session 2). The audio recording of sessions were transcribed and analyzed using rapid qualitative analysis to identify themes. Participants (n=7) raised 79 unique questions, 57 of which were deemed unanswered and categorized into 11 prioritized topics. Topics with the most questions included costs associated with care (n=9); the role of community; interactions with clinicians; and resources for patients (n=7 for each topic). Participants discussed challenging experiences, barriers, and the importance of social support when receiving abortion care. Using a community-centered approach, we identified topics and questions for future abortion-related research, to guide researchers and funders. Many questions raised by participants have already been answered in prior research, suggesting that implications of research are not clearly conveyed to those impacted the most. Using a community-centered approach, this study convened individuals who previously received abortion care in the Central Valley of California to identify key research priority topics and questions for future abortion-related research. The list of prioritized topics and questions is a guide for researchers, advocacy groups, and funders.

Examining inter‐regional and intra‐seasonal differences in wintering waterfowl landscape associations among Pacific and Atlantic flyways

The Central Valley of California (CVC) and Mid‐Atlantic (MA) in the U.S. are both critical sites for nationwide food security, and many waterfowl species annually, especially during the winter, providing feeding and roosting locations for a variety of species. Mapping waterfowl distributions, using NEXRAD, may aid in the adaptive management of important waterfowl habitat and allow various government agencies to better understand the interface between wild and domestic birds and commercial agricultural practices. We used 9 years (2014–2023) of data from the US NEXRAD network to model winter waterfowl relative abundance in the CVC and MA as a function of weather, temporal period, environmental conditions, and landcover characteristics using boosted regression tree modelling. We were able to quantify the variability in effect size of 28 different covariates across space and time within two geographic regions which are critical to nationwide waterfowl management and host a high density of nationally important commercial agriculture. In general, weather, geographic (distance to features), and landcover condition (wetness index) predictors had the strongest relative effect on predicting wintering waterfowl relative abundance in both regions, while effects of land cover composition were more regionally and temporally specific. Increased daily mean temperature was a major predictor of increasing relative waterfowl abundance in both regions throughout the winter. Increasing precipitation had differing effects within regions, increasing relative waterfowl abundance in the MA, while decreasing in general within the CVC. Increasing relative waterfowl abundance in the CVC are strongly tied to the flooding of the landscape and rice availability, whereas waterfowl in the MA, where water is less limiting, are generally governed by waste grain availability and emergent wetland on the landscape. Waterfowl relative abundance in the MA was generally higher nearer to the Atlantic coast and lakes, while in the CVC they were higher nearer to lakes. Our findings promote a better understanding of spatial associations of waterfowl to landscape features and may aid in conservation and biosecurity management protocols.

Individual-Based Ecological Particle Tracking Model (ECO-PTM) for Simulating Juvenile Chinook Salmon Migration and Survival Through the Sacramento–San Joaquin Delta

Recovery of endangered salmon species in the Central Valley of California amidst prolonged drought and climate change necessitates innovative water management actions that balance species recovery and California's water demands. We describe an individual-based ecological particle tracking model (ECO-PTM) that can be used to assess the efficacy of proposed actions. Based on a random walk theory, the model tracks individual particles’ travel time, routing and survival in a flow field simulated by the Delta Simulation Model 2 hydrodynamic module (DSM2 HYDRO). The random walk particles are parameterized to have fish-like swimming behaviors, including upstream/downstream swimming, probabilistic holding behaviors, and stochastic swimming velocities. Particle routing at key junctions is based on well-established statistical models, and route-specific survival is calculated using the XT mean free-path length model. Behavioral parameters were estimated by fitting several competing models to a multiyear dataset of travel times from acoustic tagged juvenile salmon. The model’s baseline simulations under historical flow conditions from 1991 to 2016 successfully replicated essential relationships between salmon outmigration survival and hydrodynamic conditions, consistent with previous studies and the STARS (Survival Travel Time and Routing Simulation) statistical simulation model. Simulation results for management scenarios revealed multifaceted influences on fish survival, including Delta flow, flow at key junctions, route alterations, seasons, and water availability characteristics. Importantly, these results highlight ECO-PTM’s potential to predict fish survival outcomes of proposed actions, serving as a foundation for informed future research, decision-making, and effective management strategies to enhance the survival prospects of outmigrating salmonids within the Sacramento-San Joaquin Delta ecosystem.

Terroir and rootstock effects on leaf shape in California Central Valley vineyards

Societal Impact StatementThe innumerable effects of terroir—including climate, soil, microbial environment, biotic interactions, and cultivation practice—collectively alter plant performance and production. A more direct agricultural intervention is grafting, in which genetically distinct shoot and root genotypes are surgically combined to create a chimera that alters shoot performance at a distance. Selection of location and rootstock are intentional decisions in viticulture to positively alter production outcomes. Here, we show that terroir and rootstock alter the shapes of grapevine leaves in commercial vineyards throughout the California Central Valley, documenting the profound effects of these agricultural interventions that alter plant morphology.Summary Embedded in a single leaf shape are the latent signatures of genetic, developmental, and environmental effects. In viticulture, choice of location and rootstock are important decisions that affect the performance and production of the shoot. We hypothesize that these effects influence plant morphology, as reflected in leaf shape. We sample 1879 leaves arising from scion and rootstock combinations from commercial vineyards in the Central Valley of California. Our design tests 20 pairwise contrasts between Cabernet Sauvignon and Chardonnay scions from San Joaquin, Merced, and Madera counties from vines grafted to Teleki 5C, 1103 Paulsen, and Freedom rootstocks. We quantify clear differences between Cabernet Sauvignon and Chardonnay leaves. However, we also detect a separate, statistically independent source of shape variance that affects both Cabernet Sauvignon and Chardonnay leaves similarly. We find that this other shape difference is associated with differences in rootstock and location. The shape difference that arises from rootstock and location affects the basal part of the leaf near the petiole, known as the petiolar sinus, and affects its closure. This shape effect is independent from previously described shape differences that arise from genetic, developmental, or size effects.

Comparative analysis of evapotranspiration (ET), crop water stress index (CWSI), and normalized difference vegetation index (NDVI) to delineate site-specific irrigation management zones in almond orchards

Management zones are an important aspect of precision agriculture as they help to define spatiotemporal areas that share homogenous attributes for site-specific management such as irrigation. In this study, we evaluated the potential of delineating irrigation management zones in almond (Prunus dulcis) orchards using three different variables: evapotranspiration (ET), crop water stress index (CWSI), and normalized difference vegetation index (NDVI). Multispectral and thermal images were collected on 11 days in June and July of 2020 using an instrumented aircraft flown over an almond orchard in the Central Valley of California. Obtained images were used to compute ET, CWSI, and NDVI. An unsupervised k-means clustering algorithm was used to delineate the field into management zones, and silhouette width was used to determine the optimum number of zones. Regardless of the input variable and collection date, the optimum number of irrigation management zones was identified as two. ET- and CWSI-based management zones addressed higher spatial variability in the field (up to 73.6 %) than NDVI (up to 68 %). Similarly, the level of agreement between management zones delineated using ET and CWSI was strong (kappa coefficient: 0.84 to 1.00). ET- and CWSI-based management zones also showed a trend (p < 0.1) in distinguishing the difference in the irrigation application and almond yield between the two delineated zones. This study shows that CWSI can be as effective as ET in delineating irrigation management zones, and both inputs sensitive to capture the vegetation responses to irrigation management during the summer growing season. Results from this study can be useful for growers and decision makers to practice precision irrigation management in woody perennial cropping systems.

Mapping migration habitat for western monarch butterflies reveals need for public-private approach to conservation

IntroductionIdentifying habitat of migratory species to effectively support conservation and management requires careful consideration of (1) the data used to inform habitat models, (2) the biology of the organism, (3) land tenure, and (4) the needs of the target audience.MethodsTo provide this information for western U.S. monarch butterflies, a population undergoing decline, we modeled habitat during the spring and fall migrations. Our approach controlled for biases in citizen science locality data, the principal source of monarch observation data, and incorporated needs for milkweed host plants in the spring and nectar plants in the fall.Results and DiscussionThe results showed the distribution of habitat for spring and fall migration, where the Coast Range and Central Valley in California and riparian areas throughout the range were particularly important. Just 29% of predicted habitat for spring and fall migrations, combined, overlapped between the two seasons. Although the U.S. federal government manages 53% of the land in the western U.S., government land makes up just 11.7% of the spring migration range and 23.5% of the fall migration range. State and local governments and non-governmental organizations (NGOs) manage an additional 4.2% of the spring and 4.0% of the fall migration habitat. Thus, like eastern monarchs, western monarchs rely heavily on land under private ownership for their migration and to be successful, monarch conservation efforts must embrace a public-private approach. Among federal agencies, the Bureau of Land Management (BLM; 5.9% of spring and 9.7% of fall habitat) and Forest Service (3.3% of spring and 9.2% of fall habitat) manage the greatest shares. Less than half of the government and NGO owned habitat for both migrations is managed for biodiversity conservation rather than multiple uses (spring, 46.0%; fall, 36.5%). We created custom model outputs for the BLM to highlight areas of both regional and local importance for migrating monarchs in each BLM administrative unit, enabling managers across the agency to contribute to recovery. The outcomes provide input at a relevant spatial scale to support actions such as habitat restoration, riparian zone protection, and pesticide use reduction to enhance conditions for migrating monarchs on both government and private lands.

Barn Owls as a Nature-Based Solution for Pest Control: A Multinational Initiative Around the Mediterranean and Other Regions

Pest rodents cause extensive damage to crops worldwide. Up to 40% of global crop production is lost annually to pests and diseases, with rodents accounting for 15–30% of this loss amounting to billions of dollars each year. The current method of controlling rodent populations involves the extensive use of chemical rodenticides. While effective in the short term, these chemicals pose serious environmental and health risks, leading to secondary poisoning of non-target species and other long-term negative ecological consequences, underscoring the need to adopt more sustainable pest-control measures. Nature-Based Solutions (NbSs), on the other hand, are increasingly recognized for addressing environmental challenges such as climate change, biodiversity loss, and sustainable development, and they include actions that protect, sustainably manage, and restore ecosystems. In this context, Barn Owls (Tyto alba) are highly effective as a natural pest-rodent control agents in agro-ecosystems. The species has a wide distribution and adaptability to various environments, and its diet consists predominantly of small mammals, with rodents making up from 50–60% up to even 90–95% of the diet according to different geographical regions. Each Barn Owl family can consume thousands of rodents annually, creating a high potential to reduce crop damage and infestations. Deploying nest boxes in agricultural areas can significantly increase Barn Owl populations, ensuring continuous and effective rodent control. Limitations of this solution must also be taken into consideration such as predation on rodents and small mammals that are not pests, and possible competition with other nocturnal birds of prey. Ιn the current paper, we aim to introduce the concept of owls as a NbS for pest rodent control and outline the main challenges, pitfalls, advantages, and disadvantages of implementing this solution in a new geographical region, and all the necessary in-between steps (scientific, societal, administrative, educational) that have to be followed for a successful implementation. So far, several countries have successfully implemented Barn Owl nest box schemes, with Israel and Cyprus achieving reduction in the use of pesticides by 45% and 58%, respectively, whereas the project is spreading to other Mediterranean countries (Jordan, Palestine Authority, Greece, Morocco, Spain), in palm plantations in Malaysia and USA, and in the vineyards of Napa Valley in California. The success of Barn Owl nest box programs relies on integrating scientific research, societal needs, supportive policy frameworks, and education. Barn Owl nest box programs are both bottom-up and top-down initiatives, in need of the participation of farmers and local communities to establish and deploy the Barn Owl solution. Continuous research is also necessary to explore systematically Barn owl trophic ecology, foraging and breeding ecology, interactions with agricultural landscape, and land uses in temporal and spatial scales, and challenges such as habitat suitability, availability of nesting sites, and regional ecological conditions must also be addressed.

Solar Panels as Novel Nest Sites for the European Paper Wasp Polistes dominula.

Solar energy facilities are rapidly expanding in their land-use footprint worldwide, with significant implications for biodiversity. Although the impacts of conventional solar development are often negative for biodiversity, it is possible for some species to take advantage of the novel anthropogenic structures and microhabitats provided by solar facilities. We describe the frequent nesting of non-native European paper wasps (Polistes dominula) at two solar facilities in the Central Valley of California (USA), conducting nest censuses to further investigate population density and nest siting behaviour. Active nests were found to occur at a density of 10-23 per hectare of solar facility, and paper wasps had a preference for nesting in sheltered metal torque tubes compared with the more exposed undersides of photovoltaic panels. Our study shows that P. dominula might benefit from the construction of solar energy facilities, which could have a variety of impacts on native species and surrounding agriculture that warrant further study. The European paper wasp therefore provides an example to illustrate the potential for a varied and relatively unpredictable set of ecological outcomes to follow land-use change resulting from solar energy development.

A Satellite-Based Indicator for Diagnosing Particulate Nitrate Sensitivity to Precursor Emissions: Application to East Asia, Europe, and North America.

Particulate nitrate is a major component of fine particulate matter (PM2.5) and a key target for improving air quality. Its formation is varyingly sensitive to emissions of nitrogen oxides (NOx ≡ NO + NO2), ammonia (NH3), and volatile organic compounds (VOCs). Diagnosing the dominant sensitivity is critical for effective pollution control. Here, we show that satellite observations of the NO2 column and the NH3/NO2 column ratio can effectively diagnose the dominant sensitivity regimes in polluted regions of East Asia, Europe, and North America, in different seasons, though with reduced performance in the summer. We demarcate the different sensitivity regimes using the GEOS-Chem chemical transport model and apply the method to satellite observations from the OMI (NO2) and IASI (NH3) in 2017. We find that the dominant sensitivity regimes vary across regions and remain largely consistent across seasons. Sensitivity to NH3 emissions dominates in the northern North China Plain (NCP), the Yangtze River Delta, South Korea, most of Europe, Los Angeles, and the eastern United States. Sensitivity to NOx emissions dominates in central China, the Po Valley in Italy, the central United States, and the Central Valley in California. Sensitivity to VOCs emissions dominates only in the southern NCP in the winter. These results agree well with those of previous local studies. Our satellite-based indicator provides a simple tool for air quality managers to choose emission control strategies for decreasing PM2.5 nitrate pollution.

Overview of the Current Challenges in Pulmonary Coccidioidomycosis.

Coccidioidomycosis is a disease caused by soil fungi of the genus Coccidioides, divided genetically into Coccidioides immitis (California isolates) and Coccidioides posadasii (isolates outside California). Coccidioidomycosis is transmitted through the inhalation of fungal spores, arthroconidia, which can cause disease in susceptible mammalian hosts, including humans. Coccidioidomycosis is endemic to the western part of the United States of America, including the central valley of California, Arizona, New Mexico, and parts of western Texas. Cases have been reported in other regions in different states, and endemic pockets are present in these states. The incidence of reported cases of coccidioidomycosis has notably increased since it became reportable in 1995. Clinically, the infection ranges from asymptomatic to fatal disease due to pneumonia or disseminated states. The recognition of coccidioidomycosis can be challenging, as it frequently mimics bacterial community-acquired pneumonia. The diagnosis of coccidioidomycosis is frequently dependent on serologic testing, the results of which can take several days or longer to obtain. Coccidioidomycosis continues to present challenges for clinicians, and suspected cases can be easily missed. The challenges of coccidioidomycosis disease, from presentation to diagnosis to treatment, remain a hurdle for clinicians, and further research is needed to address these challenges.

Spatiotemporal partitioning between the endangered San Joaquin kit fox and a novel mesocarnivore community in the urban environment as revealed by camera traps

Urbanization has led to the rapid formation of novel biotic communities, which via interspecific interactions, may affect niche partitioning dynamics of native, sensitive species. The endangered San Joaquin kit fox (Vulpes macrotis mutica; hereafter ‘kit fox’) is a small mesocarnivore inhabiting urban areas of the southern Central Valley of California alongside other urban mesocarnivores. These other species may pose challenges for kit foxes due to a potential lack of evolved mechanisms of defense or avoidance. To address this notion, we evaluated evidence of temporal and spatial partitioning between the kit fox and its potential predators and competitors in an urban environment. We predicted that spatial and temporal overlap would be lower between kit foxes and their predators than with their competitors. We used camera traps with scent lures at high school and college campuses across the southern San Joaquin Valley to monitor the visitation patterns of urban mesocarnivores from 2020 to 2022. We used generalized linear mixed models and AIC model selection to evaluate spatial relationships between kit foxes and other mesocarnivores and we used temporal overlap coefficients and peak activity analysis to evaluate temporal overlap. Kit foxes exhibited low spatial overlap (negative association) with Virginia opossums (Didelphis virginiana) and high spatial overlap (positive association) with domestic cats (Felis catus), domestic dogs (Canis lupus familiaris), northern raccoons (Procyon lotor), and striped skunks (Mephitis mephitis). Kit foxes exhibited low to moderate levels of temporal overlap with other species, the least of which occurring with potential predators (i.e., coyotes (C. latrans), domestic dogs). Our findings support the temporal partitioning and partially support the spatial partitioning hypothesis as potential mechanisms to promote coexistence among mesocarnivores in an urban environment.

Seasonal climate forecasts show skill in predicting winter chill for specialty crops in California

Many fruits and nuts crops in California require sufficient winter chill to break dormancy, and insufficient chill can harm fruit quantity and quality. Early information on winter chill forecast can help growers prepare for a low chill year. Here we evaluate use of dynamic climate models for chill accumulation forecast in California. Using temperature forecasts from seasonal prediction systems, we found that the multimodel forecasts can predict chill. This is evident from the anomaly correlation coefficients exceeding 0.5 between the model-predicted and reference chill values for most California regions. The forecasts correctly identified chill categories in over 50% instances in more than 40% of the Central Valley and southern parts of California. The forecasts also demonstrated skill in capturing the interannual variability of chill, especially during years with substantial decrease in chill. Additionally, the seasonal forecast can provide potentially useful crop specific chill sufficiency prediction. However, forecasts beyond a one-month lead time showed reduced forecast skills.

Factors influencing shorebird use of post‐harvest flooded rice fields in California's Sacramento Valley

AbstractBecause of the importance of the Central Valley of California, USA, to shorebirds along the Pacific Flyway, conservation investments have been made in the area's agricultural fields and managed wetlands. Increasingly, landowner incentive programs are being used to deliver shorebird habitat, presenting opportunities to answer remaining questions about which implementation strategies and field management practices are most effective at attracting birds. To provide management guidance for these investments, we collected and analyzed 5 years of data (2014–2018) on shorebird abundance in flooded rice fields enrolled in a dynamic habitat incentive program. The program incentivized flooding in fallow and post‐harvest rice fields in seasons when habitat is relatively sparse, specifically the early fall and late spring. Across nearly 9,000 field observations over 5 years, we explored the relationship between abundance and density (birds/ha) of shorebirds and vegetation cover, soil clay, landscape‐level flooding, and local flood timing, duration, and depth. We observed more shorebirds in fields that were approximately 50% flooded, had water depths of 5–10 cm, and had minimal rice straw or stubble cover, with strong or very strong evidence for each of these relationships. We found that the timing of habitat provisioning was important, with moderate evidence that earlier fall flooding and strong evidence that the duration of fall flooding was associated with higher shorebird density. We observed lower shorebird densities in locations with ample flooded rice habitat in surrounding areas, potentially because shorebirds spread out across the landscape. We found very strong evidence that flooding consistency, either at a site that was continually flooded over many months or a site that had been flooded in previous years, was associated with higher shorebird density. Soil clay content was associated with decreased observed shorebird density, potentially through its influence on the ability of shorebirds to forage for invertebrate prey. These results suggest best practices for shorebird habitat creation in agricultural landscapes, providing important information for conservation and population recovery.

Mothers’ reflections on family food habits post pandemic

The COVID-19 pandemic altered daily family routines, with the family food environment especially likely to be affected. Little is known about how families have adapted over time. The objective of the current study was to explore how family food habits evolved three years after COVID-19 was designated a pandemic. Mothers participated in an interview between March and April 2023. Reflexive thematic analysis was used to analyze the transcripts. Thirty mothers participated (97% lived in the Central Valley in California; 43% Hispanic). Themes were identified around changes in mealtime frequency, eating habits including snacking, screen time during mealtimes, and weight gain. While some unhealthy habits established during the pandemic improved, others persisted three years later. Maternal snacking, concerns about child weight gain, and overall screen time lessened after the pandemic ended, but child snacking behaviors, maternal weight gain concerns, and screen time during mealtimes continued. This research expands on the existing COVID-19 literature by examining lingering effects of the pandemic on family food habits. Findings may be helpful for health practitioners working with families to understand food related changes post-pandemic, especially those that have been particularly resistant to change.

Body mass changes of dabbling and diving ducks wintering in California

AbstractBird body mass is often used as an index of body condition and fluctuates throughout the year in response to environmental conditions and avian life‐history events. We examined the body mass of 59,572 ducks representing 13 species (7 dabbling duck species and 6 diving duck species) harvested within the 3 regions of the Central Valley in California, USA (Sacramento Valley, Suisun Marsh, San Joaquin Valley). Data collection occurred in winter during 5 hunting seasons (2014–2015, 2015–2016, 2017–2018, 2018–2019, 2019–2020). For all species, age, and sex classes, the body mass of dabbling ducks varied temporally and was lowest at the end of the hunting season in late January, declining from the beginning of the hunting season in mid‐October (northern pintail [Anas acuta]: −11.4% to −20.4%; northern shoveler [Spatula clypeata]: −3.5% to −17.3%; cinnamon teal [Anas cyanoptera]: −5.0% to −17.1%; American wigeon [Mareca americana]: −6.9% to −12.2%; American green‐winged teal [Anas carolinensis]: −5.9% to −11.9%; mallard [Anas platyrhynchos]: −1.8% to −9.6%; gadwall [Mareca strepera]: −2.2% to −8.4%). As expected, adults (after hatch‐year) were heavier than immature (hatch‐year) birds (within males: 0.6–8.6%; within females: 0.1–6.6%) and males were heavier than females (within adults: 3.1–38.6%; within immatures: 5.4–33.5%) at the end of the hunting season in all species. Within dabbling duck species, body masses did not differ among regions at the beginning of the hunting season but were heavier in the Sacramento Valley (0.5–14.4%) than other areas by the end of the hunting season. In contrast, body masses of diving ducks did not vary substantially during the hunting season or among regions. Diving ducks demonstrated inconsistent changes in mass from the beginning to the end of the season (lesser scaup [Aythya affinis]: 3.4% to 12.3%; canvasback [Aythya valisineria]: 5.1% to 6.1%; bufflehead [Bucephala albeola]: −3.2% to 1.6%; ring‐necked duck [Aythya collaris]: −4.9% to 2.6%; common goldeneye [Bucephala clangula]: −3.2% to −2.4%; ruddy duck [Oxyura jamaicensis]: −16.5% to 5.5%). The substantial temporal and spatial differences in dabbling duck body masses suggest that habitat quality (as measured by caloric value of the available food) or quantity may decline during winter and varies regionally within California's Central Valley.

Crimmigration Practices and Narratives Resisting and Justifying Mass Deportation in the Central Valley of California

Crimmigration Practices and Narratives Resisting and Justifying Mass Deportation in the Central Valley of California

Estimating the benefits of floodplain restoration to juvenile Chinook salmon in the upper San Francisco Estuary, United States, under future climate scenarios

Many river systems within the Central Valley of California have been disconnected from their floodplains, hypothesized to be partially responsible for declining Chinook salmon populations (Oncorhynchus tshawytscha). The primary floodplain of the system, Yolo By‐Pass (known regionally as “Yolo Bypass”), offered an opportunity to examine whether improved connectivity between the floodplain and river could limit negative climate change effects on salmon populations. Specifically, the top of the floodplain (Fremont Weir) is being modified to provide Sacramento River Chinook salmon better access to floodplain rearing habitat. We estimated restoration effects on the Yolo By‐Pass flood regime now and under future climate scenarios using flow rating curves. Additionally, we used temperature and flow‐specific effects on Chinook salmon population dynamics within the Yolo By‐Pass and Sacramento River complex to describe how the restoration project and climate change may interact to affect juvenile Chinook salmon biomass production. Our results indicate that the Fremont Weir restoration project will extend the frequency, timing, and duration of Yolo By‐Pass flooding. Our production model indicates that the modification will result in greater salmon entrainment rates into the Yolo By‐Pass, where salmon growth rates, survival rates, and biomass production were higher when compared to the Sacramento River main stem. The project appears to benefit all regional runs of Chinook salmon, which should help support life history diversity. Our results suggest that the weir modification should benefit native fish from the Central Valley that use floodplain habitat and that these benefits may be resilient to challenges created by a changing climate.

A comparative analysis of OpenET for evaluating evapotranspiration in California almond orchards

The almond industry in California faces water management challenges that are being exacerbated by droughts, climate change, and groundwater sustainability legislation. The Tree-crop Remote sensing of Evapotranspiration eXperiment (T-REX) aims to explore opportunities to improve precision irrigation management for woody perennial cropping systems. Almond orchards in the California Central Valley were equipped with eddy covariance flux measurements to evaluate satellite remote sensing-based evapotranspiration (RSET) models. OpenET provides high-resolution (30-m spatial and daily temporal) RSET data, synthesizing decades of research for practical water management. This study provides an evaluation of OpenET performance at six almond sites covering a large range in soils, age, and variety. It also compares OpenET ensemble evapotranspiration (ET) data with applied irrigation and precipitation records over an additional 148 almond orchards located in the Central Valley of California. Results show OpenET models, including the ensemble ET value, produced reasonable and actionable ET values, with overall coefficient of determination (R2) and mean absolute error values of 0.73- and 0.95-mm d−1 at the daily time step, respectively. However, given the temporal sampling of Landsat (8-day revisit) and the interpolation methods used, the assessed ET models had difficulty in capturing short-term variability in almond ET; for example, the rapid decline in measured ET observed as a response to lack of irrigation preceding and during almond harvest. The study also drew attention to the spatial complexity in scenarios where irrigated orchards are surrounded by hot/dry areas, causing discrepancies between measured and modeled ET values. In comparison with irrigation records, OpenET ensemble ET was capable of quantifying water input (applied irrigation + precipitation) in almond orchards to within 13 % when evaluating monthly data. Initial results presented here reinforce the idea that RSET models, such as in OpenET, are powerful tools, yet their application requires nuanced understanding and careful consideration of local conditions.

Evaluating the seasonal effects of whole orchard recycling on water movement and nitrogen retention for a newly established almond orchard: Simulation using HYDRUS-1D

Whole orchard recycling (WOR) is an emerging practice in perennial cropping systems and is an alternative to open or cogeneration burning. It is an orchard removal practice that incorporates large amounts of woody biomass back into the soil system. In this study, we utilized a soil hydrological model (HYDRUS-1D) to evaluate the seasonal effects of WOR on water movement and nitrogen (N) retention for a newly established almond orchard on a typical sandy loam soil in the Central Valley of California. Soil moisture and N content were monitored across the first five growing seasons from 2018 to 2022. The model was able to track seasonal moisture fluctuation nicely compared to observed data. Additionally, an increase in soil moisture was measured in the WOR treatments in surface soil (i.e., 0- to 15-cm depths) where biomass was incorporated, and N leaching was reduced when compared to the unamended control. Simulations suggest that with WOR, irrigation can be reduced by up to 20 % during the tree establishment stage with minimal effect on root water uptake. This reduction in applied water can increase farm water use efficiency and reduce operational expenses, e.g., cost of water and pumping. Likewise, the reduction in N leaching observed in both predicted results and laboratory analysis can further cut farm capital costs, e.g., fertilization, and lessen orchard environmental impacts. Overall, results from our simulation show a positive effect of WOR on soil ecosystem services and can potentially be a profitable strategy for orchard turnover. The results have important implications in reducing groundwater nitrate contamination in irrigated agriculture in the Central Valley of California and applicable to most parts of Southwestern United States.

Groundwater Sustainability and Land Subsidence in California’s Central Valley

The Central Valley of California is one of the most prolific agricultural regions in the world. Agriculture is reliant on the conjunctive use of surface-water and groundwater. The lack of available surface-water and land-use changes have led to pumping-induced groundwater-level and storage declines, land subsidence, changes to streamflow and the environment, and the degradation of water quality. As a result, in part, the Sustainable Groundwater Management Act (SGMA) was developed. An examination of the components of SGMA and contextualizing regional model applications within the SGMA framework was undertaken to better understand and quantify many of the components of SGMA. Specifically, the U.S. Geological Survey (USGS) updated the Central Valley Hydrologic Model (CVHM) to assess hydrologic system responses to climatic variation, surface-water availability, land-use changes, and groundwater pumping. MODFLOW-OWHM has been enhanced to simulate the timing of land subsidence and attribute its inelastic and elastic portions. In addition to extending CVHM through 2019, the new version, CVHM2, includes several enhancements as follows: managed aquifer recharge (MAR), pumping with multi-aquifer wells, inflows from ungauged watersheds, and more detailed water-balance subregions, streamflow network, diversions, tile drains, land use, aquifer properties, and groundwater level and land subsidence observations. Combined with historical approximations, CVHM2 estimates approximately 158 km3 of storage loss in the Central Valley from pre-development to 2019. About 15% of the total storage loss is permanent loss of storage from subsidence that has caused damage to infrastructure. Climate extremes will likely complicate the efforts of water managers to store more water in the ground. CVHM2 can provide data in the form of aggregated input datasets, simulate climatic variations and changes, land-use changes or water management scenarios, and resulting changes in groundwater levels, storage, and land subsidence to assist decision-makers in the conjunctive management of water supplies.