Assessing the Status and Drivers of Phytoplankton Blooms along the Riverine to Freshwater-Tidal Continuum in a Modified Delta

Springer Nature | August 1st, 2026

Shifts in phytoplankton communities, from beneficial taxa that fuel food webs to harmful taxa that degrade water quality, are often linked to anthropogenic modifi

Shifts in phytoplankton communities, from beneficial taxa that fuel food webs to harmful taxa that degrade water quality, are often linked to anthropogenic modifications to estuaries. We analyzed monitoring data from 2000 to 2023 in the heavily modified southern, landward portion of the Sacramento-San Joaquin Delta (California, USA) to determine the status and drivers of phytoplankton abundance and community composition along the riverine to freshwater tidal transition. Diatoms and green algae dominated the phytoplankton community, especially when chlorophyll a (chl-a) concentrations exceeded 16 µg L− 1. Common riverine diatoms (e.g., Cyclotella and Aulacoseira) dominated upstream riverine stations, while taxa associated with tidally influenced conditions (e.g., colonial cyanobacteria, cryptophytes) were more prevalent in western, freshwater tidal stations. The potentially toxigenic cyanobacterium, Microcystis, was present each summer, but was not associated with elevated chl-a or cyanotoxins (microcystins were detected in 12% of samples with a maximum concentration of 3.9 µg L− 1). A Bayesian ordinal regression showed that mean prior week water speeds below 0.18 m s− 1 and water temperatures above 22 ˚C were associated with the presence of Microcystis.Random forest modeling to assess factors associated with phytoplankton blooms (chl-a > 16 µg L− 1) found that mean prior week turbidity, inflows from the San Joaquin River, region, and mean prior week water temperature were important drivers of blooms. These modeling results emphasize the importance of hydrodynamics in controlling phytoplankton dynamics in lowland rivers and tidal deltas, offering insights for how anthropogenic impacts on flow regimes may affect the base of estuarine food webs.

Final Environmental Impact Statement Post-2026 Operational Guidelines and Strategies for Lake Powell and Lake Mead

U.S. Bureau of Reclamation (USBR) | July 31st, 2026

The Colorado River Basin (Basin) provides essential water supplies to approximately 40 million people, nearly 5.5 million acres of agricultural lands, and habitat for eco

The Colorado River Basin (Basin) provides essential water supplies to approximately 40 million people, nearly 5.5 million acres of agricultural lands, and habitat for ecological resources across seven states which includes broad areas in the Southwestern United States (U.S.) and Northwestern United Mexican States (Mexico). Prudent management of the Basin is critically important because the Colorado River is the foundation for diverse resources across a large geographic region and faces exceptional challenges from prolonged drought and future uncertainty. States, tribes, and Mexico rely on the Colorado River to support essential municipal, agricultural, environmental, cultural, and hydropower needs. These resources are now at significant risk: since the onset of the current drought in 2000, the Basin’s primary reservoirs, Lake Powell and Lake Mead, have fallen to historically low elevations. Several of the major reservoir- and water-management documents and agreements developed to guide Colorado River operations through the persistently dry conditions expire in 2026, including the 2007 Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead (2007 Interim Guidelines; Reclamation 2007), the 2019 Colorado River Drought Contingency Plans (Reclamation 2019), and key international agreements between the U.S. and Mexico. Despite the significance of these agreements, actions taken over the past two decades have not been sufficiently robust to prevent continued decline of the reservoirs through the prolonged drought. The Secretary of the Interior (Secretary), acting through the Bureau of Reclamation (Reclamation), proposes adoption of new guidelines and coordinated management strategies to address Lake Powell and Lake Mead through their full operating ranges to take effect when the current agreements expire in 2026. Volume I Executive Summary Cover, Abstract, Table of Contents, and Acronyms Chapter 1. Purpose and Need Chapter 2: Description of Alternatives Chapter 3: Affected Environment and Environmental Consequences Chapter 4: Consultation and Coordination Volumes II,  III, IV Click here to be taken to Reclamation for Supporting Appendices, Preparers, References, Glossary, and Index

Decadal trends in the quality of groundwater used for public drinking-water supply in California, 2004–23

U.S. Geological Survey (USGS) | July 30th, 2026

This study provides a comprehensive assessment of decadal changes in the quality of groundwater used for public drinking- water supply at 444 monitoring sites across Cali

This study provides a comprehensive assessment of decadal changes in the quality of groundwater used for public drinking- water supply at 444 monitoring sites across California during 2004–23. We assessed decadal step trends in groundwater quality for 145 water- quality constituents and geochemical indicators statewide and across geographic and land- use based network groups. We evaluated the statistical significance of directional changes (predominant increase or decrease of constituent concentrations) and the magnitude of those changes across all network groups.

Abrupt transition to irreversible damage in the overdrafted Sacramento Valley aquifer system

National Academy of Sciences (NAS) | July 27th, 2026

Groundwater extraction can cause both reversible and irreversible ground deformation, with the latter leading to permanent land subsidence and loss of groundwater storage

Groundwater extraction can cause both reversible and irreversible ground deformation, with the latter leading to permanent land subsidence and loss of groundwater storage capacity. Satellite observations of land surface deformation reveal that large areas of the Sacramento Valley abruptly transitioned from reversible to irreversible compaction over the 2020–2022 California drought—a transition not anticipated from the groundwater monitoring network alone. Subsidence rates reaching several decimeters per year and not following groundwater levels indicate lasting damage to the aquifer system and underscore the need for more conservative groundwater management. By imaging this sharp transition at the regional scale, our analysis demonstrates the potential of space-based monitoring for early detection of groundwater overdraft and the resulting loss of aquifer storage capacity worldwide.

Simulation of the Impacts of Spring Diversions on Streamflow in the Strawberry Creek Watershed, San Bernardino County, California, Using an Integrated Hydrological Model

U.S. Geological Survey (USGS) | July 27th, 2026

The Strawberry Creek watershed, in the San Bernardino Mountains of southern California, features a group of natural springs known as Arrowhead Springs that have been augm

The Strawberry Creek watershed, in the San Bernardino Mountains of southern California, features a group of natural springs known as Arrowhead Springs that have been augmented with diversions in the form of sub-horizontal borings and tunnels. Understanding the effects of these structures on streamflow through groundwater capture is crucial for managing surface-water resources in this watershed. In this study, we constructed the Strawberry Creek integrated hydrological model to increase this understanding. The Strawberry Creek integrated hydrological model is an integrated surface runoff and groundwater model, GSFLOW to simulate surface runoff and infiltration and groundwater flow. The model has 263 rows and 176 columns in each of its three layers. The model area includes the Strawberry Creek and four adjacent watersheds. The precipitation- runoff modeling system was calibrated using two streamflow gaging stations, and the groundwater and surface-water flow model was calibrated to the reported spring diversion discharge and a sparse number of groundwater- level measurements. The Strawberry Creek integrated hydrological model was run with and without diversions active, and simulated streamflow was compared, indicating that in the headwaters of Strawberry Creek, about 35 percent of the diversion flow was captured from base flow.

Marine heatwaves in the Northeast Pacific intensify landfalling atmospheric rivers on the west coast of North America

Nature Portfolio (Springer Nature) | July 23rd, 2026

Extreme precipitation along the west coast of North America is often associated with atmospheric rivers (ARs), fueled by evaporation from the ocean. When ARs interact wit

Extreme precipitation along the west coast of North America is often associated with atmospheric rivers (ARs), fueled by evaporation from the ocean. When ARs interact with marine heatwaves (MHWs), they can form compound extreme events with amplified hydrological impacts. Here, we quantify how MHWs influence the intensity and precipitation of landfalling ARs through thermodynamic air–sea interaction processes. We use high-resolution regional coupled ocean–atmosphere ensemble simulations to isolate the influence of large-scale MHW-related sea surface temperature (SST) anomalies while constraining the synoptic-scale atmospheric circulation. Focusing on well-documented AR events during the 2013–16 Northeast Pacific MHW, we show that anomalously warm SSTs enhance evaporation and lower-tropospheric moisture availability, leading to a robust increase in integrated vapor transport and intensified landfalling ARs. The enhanced moisture transport results in earlier onset and substantially increased coastal precipitation, particularly over drought-vulnerable regions of California. Moisture-budget diagnostics demonstrate that this amplification arises from a direct thermodynamic response to SST anomalies, rather than indirect modulation through changes in large-scale atmospheric circulation. Insights gained from this case study identify a thermodynamic pathway linking MHWs and ARs, highlighting the role of persistent oceanic thermal anomalies in shaping compound hydrological extremes under continued climate warming.

Urban water affordability crisis exacerbated by climate change

NATure Portfolio (Springer Nature) | July 8th, 2026

Physical water system consolidation alone cannot resolve drinking water failure in California’s San Joaquin Valley

Nature Portfolio (Springer Nature) | July 2nd, 2026

Small community water systems in California’s San Joaquin Valley disproportionately fail to provide safe drinking water, with most serving disadvantaged communities and

Small community water systems in California’s San Joaquin Valley disproportionately fail to provide safe drinking water, with most serving disadvantaged communities and lacking the technical, managerial, and financial capacity to maintain compliance. The State Water Board designates such systems as failing when they have documented violations of drinking water standards or cannot reliably deliver safe water. Physical consolidation, which involves connecting a smaller failing system to a larger provider through new pipeline infrastructure, is the primary long-term solution promoted by state regulators. Here, we assess consolidation feasibility and capital costs across four counties (Kern, Kings, Tulare, and Fresno) via the state’s 2024 screening methodology. The methodology identifies smaller failing and at-risk systems as candidates for joining a larger receiving system with sufficient capacity. Among the 210 eligible systems, 114 (54%) matched a receiving system within three miles, with an estimated total capital need of $413.5 million. Nearly all identified pairs met state funding viability thresholds. The remaining 96 systems, including 49 classified as failing, lacked an eligible receiving partner and will require alternative solutions. Physical consolidation is necessary but insufficient for achieving safe drinking water access across the region.

Loss and Transformation of Coastal Wetlands due to Global Change in the Conterminous United States: Past, Present, and Future

Publisher not available | June 26th, 2026

Coastal wetlands are being transformed by global change, impacting the ecological and societal benefits provided by these ecosystems. Synthesizing knowledge of historical

Coastal wetlands are being transformed by global change, impacting the ecological and societal benefits provided by these ecosystems. Synthesizing knowledge of historical and expected future transformations in coastal wetlands can help inform forward-looking planning and stewardship efforts. Here, we review anticipated future ecological transformations in coastal wetlands of the conterminous United States and contrast them with past transformations. We examine trends at the national scale but focus in detail on the following six wetland-rich regions: (1) Everglades, (2) Mississippi River delta, (3) Chesapeake Bay, (4) San Francisco Estuary, (5) Puget Sound, and (6) Great Lakes. This review is among the first to integrate and compare coastal wetland transformations in the Great Lakes with their oceanic counterparts. Between 1850 and 1970, wetland losses across the nation were high because coastal wetlands were viewed as flooded wastelands needing to be drained, filled, or excavated to make room for other land uses. Over the last 50 years, growing public and scientific appreciation of the ecological and societal benefits provided by coastal wetlands has fostered tremendous gains in wetland restoration and legal protection. Looking to the future, climate change and accelerated sea-level rise have become critical threats to coastal wetlands and are emerging as major drivers of ecological loss and transformation. This review synthesizes regional knowledge regarding past, present, and future changes to help coastal scientists, environmental managers, and the public better anticipate and prepare for future coastal wetland transformations due to climate change, accelerated sea-level rise, land-use change, and other aspects of global change.

Evaluating groundwater quality influences from oil field operations and other anthropogenic activities in an urban setting, Santa Fe Springs, California

Science of the Total Environment (Elsevier) | June 22nd, 2026

Groundwater quality is often affected by anthropogenic activities in urban settings. This study examines groundwater quality in and around the Santa Fe Springs Oil Field

Groundwater quality is often affected by anthropogenic activities in urban settings. This study examines groundwater quality in and around the Santa Fe Springs Oil Field in Los Angeles County, California, where oil and gas production commonly intersects with high density industrial, commercial and residential land uses. Utilizing a combination of new and historical data, we evaluated potential pathways that would allow for oil field formation fluids to migrate into groundwater and whether mixing may have occurred based on the distribution of groundwater and oil field formation fluid tracers in samples. Samples were analyzed for a wide array of constituents including volatile organic compounds, light hydrocarbons, major ions, and various isotopic compositions. Despite evidence of oil field infrastructure providing potential pathways of migration via uncemented annular spaces, casing breaches and historical disposal of oil field formation water in surface ponds, the distribution and occurrence of stable isotopes of water, chloride, boron, and total dissolved solids do not indicate mixing of oil field formation water and groundwater. However, methane isotopic signatures and the presence of heavier alkanes suggest gas from oil-bearing formations have migrated from depth via oil field well infrastructure. Volatile organic compound detections were mainly from manufactured compounds unrelated to oil and gas production, with a relatively limited number of petroleum hydrocarbons also detected. Volatile organic compounds were generally found in wells tapping shallow, modern aged groundwater, indicating anthropogenic activities occurring at or near land surface as the source. Study results suggest that while oil field infrastructure provides migration pathways for oil field formation fluids to be introduced into groundwater, urban land uses not related to oil and gas production are the primary drivers of groundwater quality degradation.