Thirstwaves: Prolonged Periods of Agricultural Exposure to Extreme Atmospheric Evaporative Demand for Water

American Geophysical Union (AGU) | March 20th, 2025

Global atmospheric evaporative demand has increased, impacting agricultural productivity and water use. Traditionally, trend assessments have been limited to total evapor

Global atmospheric evaporative demand has increased, impacting agricultural productivity and water use. Traditionally, trend assessments have been limited to total evaporative demand, overlooking shifts in daily extremes, which are meaningful for agrohydrological outcomes yet largely unknown. Here, using a fully physical metric of evaporative demand, that is, standardized short crop reference evapotranspiration, we introduce the concept of thirstwaves—prolonged periods of extremely high evaporative demand—and analyze their characteristics during 1981–2021 growing seasons for the conterminous US. Findings show that long-term mean spatial patterns demonstrated by thirstwave characteristics do not follow that of total or mean evaporative demand. Weighted for cropland area harvested, thirstwave intensity, duration, and frequency have increased by 0.06 mm d−1 decade−1, 0.10 days decade−1, and 0.39 events decade−1, respectively during 1981–2021. Statistically significant trends appear across 17%, 7%, and 23% of cropland area for intensity, frequency, and duration. Not only have thirstwaves increased in severity, but the likelihood of no thirstwaves occurring during the growing season has significantly decreased. Our work proposes a novel metric to describe periods of extremely elevated evaporative demand and presents a systematic analysis of such conditions historically for US croplands.

Thirty-Five Years of Water Policy: The 1973 National Water Commission and Present Challenges

Congressional Research Service (CRS) | May 11th, 2009

Concern about the availability and use of water to support the nation’s people, economy, and environment has bolstered interest in establishing a national water commiss

Concern about the availability and use of water to support the nation’s people, economy, and environment has bolstered interest in establishing a national water commission. The commission structure proposed in recent legislation (e.g., H.R. 135) is similar to that of the 1968-1973 National Water Commission (NWC or Commission). As proposed in H.R. 135, the commission would assess future water demands, study current management programs, and develop recommendations for a comprehensive water strategy. Questions about a commission as an effective model and which topics a commission might consider have raised interest in assessing what the NWC recommended in its 1973 report, Water Policies for the Future, and how the issues that it identified have evolved. The NWC recommended addressing the interconnection between water development and the natural environment, implementing a “users pay” or “beneficiary pays” approach, accomplishing water quality improvements, and adapting governance and organizations to meet water challenges. Since 1973, progress has been made in some of these areas; however, few actions can be traced directly to the NWC’s recommendations. Nonetheless, the influence of the NWC on the evolution of water policy cannot be dismissed. Many of the problems that the Commission identified remain today, and some actions since 1973 have moved water policy toward alignment with NWC recommendations; others have moved it in the opposite direction of NWC recommendations. Shifts in institutional arrangements in general have reduced coordination of federal water agency activities and in many ways have moved away from NWC-recommended multi-objective or river basin planning. State-federal tensions over proper and respective roles continue to cloud resolution of difficult water resource issues and complicate coordination efforts. While many support better coordination of federal water activities and a clearer national “vision” for water management, Congress has not enacted overarching water policy legislation since the 1965 Water Resources Planning Act. Instead, water policy has largely evolved through executive and judicial actions, in many cases in response to piecemeal legislation. Congress continually modifies federal water projects through amendments to existing projects and programs through Water Resources Development Acts (WRDAs), Reclamation acts, water quality legislation, and appropriations decisions. Incremental and ad hoc evolution of water policy, however, is not surprising. Water management is complicated by past decisions and investments affecting a wide range of stakeholders pursuing different goals. Specifically, federal and state laws and regulations, local ordinances, tribal treaties, contractual obligations, and economies dependent on existing water use patterns and infrastructure all affect water management. Attempts to untangle such complexities involve many constituencies with differing interests, and success is difficult to achieve. Expectations for a commission to achieve change in a complex system resistant to transformation may be unreasonable; instead, the influence of a commission may lie in how its recommendations combine with other drivers to support policy evolution. This CRS report presents the NWC’s recommendations and analyzes how issues targeted by the recommendations have evolved during the intervening years. The report focuses on key federal-level recommendations, thereby targeting what has been accomplished since 1973, what issues remain unresolved, and what additional concerns have developed.

Thousands of domestic and public supply wells face failure despite groundwater sustainability reform in California’s Central Valley

Nature Portfolio (Springer Nature) | September 8th, 2023

Three-dimensional geologic mapping of the Cenozoic basin fill, Amargosa Desert basin, Nevada and California

U.S. Geological Survey (USGS) | July 1st, 2014

Understanding the subsurface geologic framework of the Cenozoic basin fill that underlies the Amargosa Desert in southern Nevada and southeastern California has been impr

Understanding the subsurface geologic framework of the Cenozoic basin fill that underlies the Amargosa Desert in southern Nevada and southeastern California has been improved by using borehole data to construct three-dimensional lithologic and interpreted facies models. Lithologic data from 210 boreholes from a 20-kilometer (km) by 90-km area were reduced to a limited suite of descriptors based on geologic knowledge of the basin and distributed in three-dimensional space using interpolation methods. The resulting lithologic model of the Amargosa Desert basin portrays a complex system of interfingered coarse- to fine-grained alluvium, playa and palustrine deposits, eolian sands, and interbedded volcanic units. Lithologic units could not be represented in the model as a stacked stratigraphic sequence due to the complex interfingering of lithologic units and the absence of available time-stratigraphic markers. Instead, lithologic units were grouped into interpreted genetic classes, such as playa or alluvial fan, to create a three-dimensional model of the interpreted facies data. Three-dimensional facies models computed from these data portray the alluvial infilling of a tectonically formed basin with intermittent internal drainage and localized regional groundwater discharge. The lithologic and interpreted facies models compare favorably to resistivity, aeromagnetic, and geologic map data, lending confidence to the interpretation.

Three-Dimensional Hydrogeologic Framework Model of the Russian River Watershed, California

U.S. Geological Survey (USGS) | December 19th, 2024

The U.S. Geological Survey (USGS) was invited by the California State Water Resources Control Board and Sonoma County Water Agency to cooperate on a scientific investigat

The U.S. Geological Survey (USGS) was invited by the California State Water Resources Control Board and Sonoma County Water Agency to cooperate on a scientific investigation to evaluate the groundwater resources of the Russian River watershed and to develop tools to better understand and manage the groundwater system. The purpose of this report is to describe the development of a digital 3D HFM of the Russian River watershed. Such a model will help fully conceptualize the 3D subsurface configuration of aquifers and also may be used as the primary geologic input to numerical simulations of the hydrologic system. The 3D HFM, and data used to construct the 3D HFM, can be found in the following data release (Fenton and others, 2022).

Tijuana River Contamination Crisis: A Five-Pillar Framework for Binational Solutions

San Diego Regional Chamber of Commerce | March 14th, 2026

The persistent contamination of the Tijuana River and nearby Pacific coastline stems from historic chronic infrastructure failures, insufficient operations and maintenanc

The persistent contamination of the Tijuana River and nearby Pacific coastline stems from historic chronic infrastructure failures, insufficient operations and maintenance (O&M), and fragmented binational governance. This report presents both a synopsis of the problem and a comprehensive, long-term, and binational solution built around five mutually reinforcing pillars. Together, these pillars create a roadmap for eliminating dry-weather transboundary sewage flows, restoring coastal water quality, and establishing accountable and financially sustainable wastewater management in the San Diego-Tijuana region. By addressing these challenges comprehensively, the roadmap safeguards public health, supports economic resilience, and improves the overall quality of life for the communities and businesses across the San Diego-Tijuana binational region. 

Tijuana River Valley Historical Ecology Investigation

San Francisco Estuary Institute (SFEI) | January 2nd, 2017

The Tijuana River Valley Historical Ecology Investigation addresses a regional data gap by reconstructing the landscape and ecosystem characteristics of the river valley

The Tijuana River Valley Historical Ecology Investigation addresses a regional data gap by reconstructing the landscape and ecosystem characteristics of the river valley prior to the major modifications of the late 19th and 20th centuries. The research presented here, funded by the California State Coastal Conservancy, supplies foundational information at the regional and system scale about how the Tijuana Estuary, River, and valley looked and functioned in the recent past, as well as how they have changed over time. The ultimate goal of this study is to provide a new tool and framework that, in combination with contemporary research and future projections, can support and guide ongoing restoration design, planning, and management efforts in the valley.

Time Limits for Western Water Rights

Natural Resources and Environment (SSRN) | November 1st, 2022

Time-lagged impacts of extreme, multi-year drought on tidal salt marsh plant invasion

Ecological Society of America (ESA) | June 11th, 2020

Climate change is projected to increase the frequency of extreme drought events, which can have dramatic consequences for ecosystems. Extreme drought may interact with o

Climate change is projected to increase the frequency of extreme drought events, which can have dramatic consequences for ecosystems. Extreme drought may interact with other stressors such as invasion by non-native species, yet little research has explored these dynamics. Here, we examine the physical mechanisms and temporal scale underlying a dieback of an invasive non-native plant, Lepidium latifolium, in tidal salt marshes of the San Francisco Bay, California, USA, during an extreme, multi-year drought occurring from 2012 to 2015. Using generalized additive mixed models (GAMMs), we explored the relationship between eight years of estuarine salinity data and five years of L. latifolium density data from three marshes spanning a gradient of salinity across the San Francisco Bay. We found a significant time-lagged (3 yr) effect of estuarine salinity on L. latifolium density, with high salinities preceding reductions in L. latifolium densities and low salinities preceding increases. The most dramatic change in stem density, a 54% reduction in 2015, was preceded by a salinity increase of 43% from 2011 to 2012. We found the L. latifolium decline was driven by impacts on mature, rather than young, plants. Additionally, we tested the importance of local precipitation in driving L. latifolium densities in a one-season rain exclusion experiment. We found 100% exclusion of precipitation during one rainy season (January–mid-May) did not have a significant impact on densities of mature stands of L. latifolium. Our finding that estuarine salinity was a key driver of L. latifolium invasion dynamics suggests sea level rise, like extreme drought, may hinder L. latifolium invasion, as it will also raise estuarine salinities. Further, our study highlights the importance of temporal lags in understanding climate change impacts on biological invasions, which has received very little study to date.

Time-varying land subsidence detected by radar altimetry: California, Taiwan and north China

Nature Portfolio (Springer Nature) | June 21st, 2016

Contemporary applications of radar altimetry include sea-level rise, ocean circulation, marine gravity, and icesheet elevation change. Unlike InSAR and GNSS, which are wi

Contemporary applications of radar altimetry include sea-level rise, ocean circulation, marine gravity, and icesheet elevation change. Unlike InSAR and GNSS, which are widely used to map surface deformation, altimetry is neither reliant on highly temporally-correlated ground features nor as limited by the available spatial coverage, and can provide long-term temporal subsidence monitoring capability. Here we use multi-mission radar altimetry with an approximately 23 year data-span to quantify land subsidence in cropland areas. Subsidence rates from TOPEX/POSEIDON, JASON-1, ENVISAT, and JASON-2 during 1992–2015 show time-varying trends with respect to displacement over time in California’s San Joaquin Valley and central Taiwan, possibly related to changes in land use, climatic conditions (drought) and regulatory measures affecting groundwater use. Near Hanford, California, subsidence rates reach 18 cm yr with a cumulative subsidence of 206 cm, which potentially could adversely affect operations of the planned California High-Speed Rail. The maximum subsidence rate in central Taiwan is 8 cm yr. Radar altimetry also reveals time-varying subsidence in the North China Plain consistent with the declines of groundwater storage and existing water infrastructure detected by the Gravity Recovery and Climate Experiment (GRACE) satellites, with rates reaching 20 cm yr and cumulative subsidence as much as 155 cm.