Hydroclimatic Extremes as Challenges for the Water Management Community: Lessons from Oroville Dam and Hurricane Harvey

American Meteorological Society (AMS) | December 31st, 2018

Record-breaking extreme storms were a hallmark of 2017 in the United States. An extremely wet winter on the West Coast and brutally damaging hurricane season in

Record-breaking extreme storms were a hallmark of 2017 in the United States. An extremely wet winter on the West Coast and brutally damaging hurricane season in the U.S. Southeast and the Caribbean challenged communities and power-, water- and flood-management systems in ways that raised climate change concerns. Among the most severe were two periods of heavy precipitation and high runoff that exposed dangerous weaknesses in water management infrastructure and land use practices in California and Texas. In California, a record-breaking string of atmospheric river landfalls and remarkably wet winter conditions came close to causing a catastrophic failure of the emergency spillway at Oroville Dam (France et al. 2018; Abbott 2018; White et al. 2019) and less publicized concerns elsewhere (Holland et al. 2018; CNRFC 2017). In Texas, near record-doubling rainfall accumulations from Hurricane Harvey led to massive flooding (Blake and Zelinsky 2018) and dam safety challenges in Houston (Wax-Thibodeaux et al. 2017). We use these events as examples to ground the concept that attribution studies, with careful management-focused framing, can help water management better navigate such unprecedented extremes. *Chapter from the American Meteorological Society's Explaining Extreme Events of 2017 from a Climate Perspective.

Hydrological Intensification Will Increase the Complexity of Water Resource Management

American Geophysical Union (AGU) | March 9th, 2022

Climate change is intensifying the hydrologic cycle, resulting in an increase in floods and droughts. These changes increase the complexity of water resource management t

Climate change is intensifying the hydrologic cycle, resulting in an increase in floods and droughts. These changes increase the complexity of water resource management that must balance between releasing water to reduce flood risk and storing water for long periods without precipitation. Using updated climate model projections, we show that the amount of precipitation during events will become larger combined with longer dry periods where the daily evaporative demand exceeds precipitation for much of the Earth's surface. Additionally, for the late 21st century, a large portion of the years will be hydrologically intense in major river basins, resulting in conditions that deviate from those for which infrastructure and management policies were developed.

Hydrometeorological characteristics of rain-on-snow events associated with atmospheric rivers

American Geophysical Union (AGU) | March 29th, 2016

Atmospheric rivers (ARs) are narrow, elongated, synoptic corridors of enhanced water vapor transport that play an important role in regional weather/hydrology. Rain-on-s

Atmospheric rivers (ARs) are narrow, elongated, synoptic corridors of enhanced water vapor transport that play an important role in regional weather/hydrology. Rain-on-snow (ROS) events during ARs present enhanced flood risks due to the combined effects of rainfall and snowmelt. Focusing onCalifornia’s Sierra Nevada, the study identifies ROS occurrences and their connection with ARs during the 1998–2014 winters. AR conditions, which occur during 17% of all precipitation events, are associated with 50% of ROS events (25 of 50). Composite analysis shows that compared to ARs without ROS, ARs with ROS areon average warmer by ~2 K, with snow water equivalent loss of ~0.7 cm/d (providing 20% of the combined water available for runoff) and ~50% larger streamflow/precipitation ratios. Atmospheric Infrared Sounderretrievals reveal distinct offshore characteristics of the two types of ARs. The results highlight the potential value of observing these events for snow, rain, and flood prediction.

Identifying American climate change free riders and motivating sustainable behavior

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

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

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

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

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

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

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

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

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

Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans

American Association for the Advancement of Science (AAAS) | July 16th, 2004

Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed

Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell–forming species. CaCO3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO3 dissolution rate for the global oceans is approximately 0.5  0.2 petagrams of CaCO 3-C per year, which is approximately 45 to 65% of the export production of CaCO 3.

Impact of current and warmer climate conditions on snow cover loss in burned forests

American Association for the Advancement of Science (AAAS) | September 17th, 2025

Wildfires are increasingly burning in snow-dominated watersheds and can alter snowmelt dynamics. However, the spatial variability of snow cover loss in burned forests has

Wildfires are increasingly burning in snow-dominated watersheds and can alter snowmelt dynamics. However, the spatial variability of snow cover loss in burned forests has been under characterized. Here, we use remotely sensed snow data to show that, under average winter conditions, snow melts earlier in the first year postfire in 99% of the snow zone. Postfire snow cover loss is more extreme in relatively low-elevation, warm environments compared to that in high-elevation, cold regions. Under +2°C of warming, 73% of the snow zone would experience more extreme earlier postfire snowmelt compared to historically average conditions. Regions with the largest shift earlier in postfire snowmelt timing under average climate conditions also have the largest shift earlier in postfire snowmelt under +2°C warming. The spatial variability in postfire snowmelt timing and exacerbated impact in projected warmer winters affect ecosystem water availability, snow albedo feedbacks, and snowmelt runoff forecasting essential to water resource management.

Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming

Wiley | February 21st, 2013

Ocean acidification represents a threat to marine species worldwide, and forecasting the ecological impacts of acidification is a high priority for science, management, a

Ocean acidification represents a threat to marine species worldwide, and forecasting the ecological impacts of acidification is a high priority for science, management, and policy. As research on the topic expands at an exponential rate, a comprehensive understanding of the variability in organisms' responses and corresponding levels of certainty is necessary to forecast the ecological effects. Here, we perform the most comprehensive meta‐analysis to date by synthesizing the results of 228 studies examining biological responses to ocean acidification. The results reveal decreased survival, calcification, growth, development and abundance in response to acidification when the broad range of marine organisms is pooled together. However, the magnitude of these responses varies among taxonomic groups, suggesting there is some predictable trait‐based variation in sensitivity, despite the investigation of approximately 100 new species in recent research. The results also reveal an enhanced sensitivity of mollusk larvae, but suggest that an enhanced sensitivity of early life history stages is not universal across all taxonomic groups. In addition, the variability in species' responses is enhanced when they are exposed to acidification in multi‐species assemblages, suggesting that it is important to consider indirect effects and exercise caution when forecasting abundance patterns from single‐species laboratory experiments. Furthermore, the results suggest that other factors, such as nutritional status or source population, could cause substantial variation in organisms' responses. Last, the results highlight a trend towards enhanced sensitivity to acidification when taxa are concurrently exposed to elevated seawater temperature.

Impacts of Predicted Sea-Level Rise and Extreme Storm Events on the Transportation Infrastructure in the San Francisco Bay Region

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

Literature concerning the potential effect of climate change (sea‐level rise inundation and 100‐year storm events) on the San Francisco Bay region’s transportation

Literature concerning the potential effect of climate change (sea‐level rise inundation and 100‐year storm events) on the San Francisco Bay region’s transportation infrastructure is reviewed. Currently available geographical information system data is employed, and a review of how those datasets have been used in previous studies is reported. The second part of this paper presents methods. They include a higher‐resolution digital elevation model for the Bay Area; a new approach using a digital surface model is introduced to improve the surface elevations of features and better calculate the risk of over‐topping by sea level shifts and storm surges. A metric to assess change in the transportation infrastructure is introduced that calculates accessibility of first responders to the population at large. Sea level rise is incremented to the expected 1.4 meters in tandem with a 100‐year flood to analyze the extent to which transportation assets are at risk of inundation. The increased travel time from first responder locations to all neighborhoods in the region is measured for each iteration of the model. Local accessibility analysis for the entire San Francisco Bay region is performed to provide a synoptic view. Two localities are chosen to view in detail the impact on first‐responder accessibility caused by sea level rise and a 100‐year storm event. Next, the regional vulnerability of the transportation network to these events is assessed. This is accomplished by creating nodes that are the intersections of the major regional highways that surround the Bay. The loss of accessibility is measured by calculating the changes in travel time between these major nodes through iterations of our inundation model. Finally, the accessibility impacts to the hinterland from the major highway intersections for each peak water level iteration is determined, calculating the first and last 20 minutes of an origin‐destination journey.