Mapping the global threat of land subsidence

American Association for the Advancement of Science (AAAS) | January 1st, 2021

Subsidence, the lowering of Earth's land surface, is a potentially destructive hazard that can be caused by a wide range of natural or anthropogenic triggers but mainly r

Subsidence, the lowering of Earth's land surface, is a potentially destructive hazard that can be caused by a wide range of natural or anthropogenic triggers but mainly results from solid or fluid mobilization underground. Subsidence due to groundwater depletion is a slow and gradual process that develops on large time scales (months to years), producing progressive loss of land elevation (centimeters to decimeters per year) typically over very large areas (tens to thousands of square kilometers) and variably affects urban and agricultural areas worldwide. Subsidence permanently reduces aquifer-system storage capacity, causes earth fissures, damages buildings and civil infrastructure, and increases flood susceptibility and risk. During the next decades, global population and economic growth will continue to increase groundwater demand and accompanying groundwater depletion  and, when exacerbated by droughts, will probably increase land subsidence occurrence and related damages or impacts. To raise awareness and inform decision-making, we evaluate potential global subsidence due to groundwater depletion, a key first step toward formulating effective land-subsidence policies that are lacking in most countries worldwide.

Maps, Models, and Mystery: Interconnected Groundwater and the Public Trust

American Bar Association (ABA) | August 10th, 2019

Walk into the office of any water law practitioner, anywhere, and you might think you made a wrong turn and walked into the office of your local cartographer. We are a p

Walk into the office of any water law practitioner, anywhere, and you might think you made a wrong turn and walked into the office of your local cartographer. We are a profession that depends on, and you might even say reveres, a good map. Rights to water flowing in surface streams are fundamentally defined by geography, and maps have long been a requirement of appropriation and essential evidence of riparian ownership. In turn, injury to a surface water right is determined by physics, as the topography of the land establishes the linear relation of impacts from other diversions, whether it be upstream (cause), or downstream (affected). In homage to these principles, some hydrologists will orient their maps top-to-bottom as upstream to downstream, rather than north to south. In our practice, gravity is our compass. Upending the convenient simplicity of rivers and streams flowing from mountaintop to ocean are alluvial and glacial valleys, in which unconsolidated sediment serve as giant sponges and blocks of fractured rock contain hidden stores of oftentimes ancient waters. Through these geologic features, hidden beneath the surface, water percolates, flows, and moves across the landscape. These subsurface waterbodies interconnect with surface streams and changes in the groundwater basin, whether due to drought or artificial extractions, and influence surface flow on a time scale ranging from minutes to centuries. To understand the relationship with any hope of precision, we need much more than a map; we need a hydrogeologist and a whole lot of data. All of this is by way of introducing two themes of emerging law in California that stand to influence trends beyond the state: (1) the legal relevance of interconnected groundwater to surface flows in protecting instream uses, and (2) recognition in the law of the need to understand and manage these interconnected waters.

Marine heat wave and multiple stressors tip bull kelp forest to sea urchin barrens

Nature Portfolio (Springer Nature) | October 21st, 2019

Extreme climatic events have recently impacted marine ecosystems around the world, including foundation species such as corals and kelps. Here, we describe the

Extreme climatic events have recently impacted marine ecosystems around the world, including foundation species such as corals and kelps. Here, we describe the rapid climate-driven catastrophic shift in 2014 from a previously robust kelp forest to unproductive large scale urchin barrens in Northern California. Bull kelp canopy was reduced by >90% along more than 350 km of coastline. Twenty years of kelp ecosystem surveys reveal the timing and magnitude of events, including mass mortalities of sea stars (2013-), intense ocean warming (2014–2017), and sea urchin barrens (2015-). Multiple stressors led to the unprecedented and long-lasting decline of the kelp forest. Kelp deforestation triggered mass (80%) abalone mortality (2017) resulting in the closure in 2018 of the recreational abalone fishery worth an estimated $44 M and the collapse of the north coast commercial red sea urchin fishery (2015-) worth $3 M. Key questions remain such as the relative roles of ocean warming and sea star disease in the massive purple sea urchin population increase. Science and policy will need to partner to better understand drivers, build climate-resilient fisheries and kelp forest recovery strategies in order to restore essential kelp forest ecosystem services.

Marine heatwaves need clear definitions so coastal communities can adapt

Nature Portfolio (Springer Nature) | April 3rd, 2023

Mark/Recapture Experiments at Clifton Court Forebay to Estimate Pre-Screening Loss to Juvenile Fishes: 1976-1993

California Department of Fish and Wildlife (CDFW) | September 30th, 1997

From October 1976 through November 1993, the California Department of Fish and Game conducted mark/recapture experiments at Clifton Court Forebay, designed to estimate pr

From October 1976 through November 1993, the California Department of Fish and Game conducted mark/recapture experiments at Clifton Court Forebay, designed to estimate pre-screen loss to entrained juvenile fishes. Ten studies were conducted; eight evaluated losses to hatchery-reared juvenile chinook salmon, and two evaluated losses to hatchery-reared juvenile striped bass. Pre-screen loss was calculated from the proportion of marked fish released at the radial gates that were subsequently recaptured during salvage operations at Skinner Fish Facility. The proportion was adjusted for handling mortality, fish facility louver effiCiency, and any subsampling at the facility. Studies were conducted across a wide range of environmental conditions and State Water Project operations, with a wide range in the size ofexperimental fish. Pre-screen loss estimates for juvenile chinook salmon were 63-99%. Potential biases in estimates of pre-screen loss may be due to (1) the calculation for pre-screen loss, (2) underrepresentative and over-representative salvage of experimental fish at Skinner Fish Facility, and (3) the introduction of experimental fish directly into Clifton Court Forebay. A multiple-regression analysis of pre-screen loss to juvenile salmon showed that 91% of the variance in pre-screen loss can be explained by export rate, experimental fish size, and water temperature. 

Marsh Sediment in Translation: A Review of Sediment Transport Across a Natural Tidal Salt Marsh in Northern San Francisco Bay

University of California, Davis (UC Davis) | March 15th, 2025

Deposition of inorganic sediment is essential for the sustainability of tidal salt marshes. Understanding variability in sediment sources and the processes of sediment de

Deposition of inorganic sediment is essential for the sustainability of tidal salt marshes. Understanding variability in sediment sources and the processes of sediment delivery to salt marshes are high priorities for decision-makers responsible for managing sediment and conserving and restoring marshes.

Martis Valley Groundwater Basin Sustainable Groundwater Management Act Alternative Submittal

Truckee Donner Public Utility District (TDPUD) | December 22nd, 2016

Matching Water Quality to Use (Resource Management Strategy)

California Department of Water Resources (DWR) | July 29th, 2016

Matching water quality to use is a management strategy that recognizes that not all water uses require the same water quality. One common measure of water quality is its

Matching water quality to use is a management strategy that recognizes that not all water uses require the same water quality. One common measure of water quality is its suitability for an intended use; a water quality constituent often is only considered a contaminant when that constituent adversely affects the intended use of the water. High-quality water sources can be used for drinking and industrial purposes that benefit from higher quality water and lesser quality water can be adequate for some uses. For example, a water supplier chooses to use a groundwater source for municipal use, which requires less treatment before delivery, rather than a natural stream. The potential benefit to the municipal user could be reduced disinfection byproducts in the delivered drinking water source and a secondary benefit would accrue to the natural riparian system because water would be left instream. Further, some new water supplies, such as recycled water, can be treated to a wide range of purities that can be matched to different uses. The use of other water sources, like recycled water, can serve as a new source of water that substitutes for uses not requiring potable water quality. Instream uses are directly influenced by discharges from wastewater treatment and stormwater flows and these source discharges can provide benefits and challenges to uses such as aquatic life and recreation.

Maxey-Eakin Methods for Estimating Groundwater Recharge in the Fenner Watershed, Southeastern California

U.S. Department of Energy (DOE) | May 15th, 2000

Recent review comments by the U.S. Geological Survey, Water Resources Division on the Cadiz Groundwater Storage and Dry-Year Supply Program Draft Environmental Planning

Recent review comments by the U.S. Geological Survey, Water Resources Division on the Cadiz Groundwater Storage and Dry-Year Supply Program Draft Environmental Planning Report were accompanied by an independent recharge estimate to the Fenner Basin based on a Maxey-Eakin method. The following report has analyzed WRD's recharge estimates and concludes that those results greatly underestimate annual recharge and lack credibility. Among the reasons outlined are 1) WRDÕs lack of geographic scale and context when analyzing precipitation-elevation data, 2) WRD's use of an uncalibrated Maxey-Eakin model, and 3) WRD's lack of direct observational experience in the eastern Mojave-Fenner Basin region. This report presents a more exhaustive analysis of data, supported by direct field observations, and estimates recharge using a calibrated Maxey-Eakin model. This report concludes that the possible range in annual groundwater replenishment rates to the Fenner Basin are between 7864 acre-ft and 29,185 acre-ft. The lower limit is a worst-case-scenario. This range is consistent with original recharge estimates calculated and presented in the Cadiz Groundwater Storage and Dry-Year Supply Program Draft Environmental Planning Report.

Maximizing ENSO as a source of western US hydroclimate predictability

Climate Dynamics (Springer) | October 16th, 2019

Until recently, the El Niño–Southern Oscillation (ENSO) was considered a reliable source of winter precipitation predictability in the western US, with a historically

Until recently, the El Niño–Southern Oscillation (ENSO) was considered a reliable source of winter precipitation predictability in the western US, with a historically strong link between extreme El Niño events and extremely wet seasons. However, the 2015–2016 El Niño challenged our understanding of the ENSO-precipitation relationship. California precipitation was near-average during the 2015–2016 El Niño, which was characterized by warm sea surface temperature (SST) anomalies of similar magnitude compared to the extreme 1997–1998 and 1982–1983 El Niño events. We demonstrate that this precipitation response can be explained by El Niño’s spatial pattern, rather than internal atmospheric variability. In addition, observations and large-ensembles of regional and global climate model simulations indicate that extremes in seasonal and daily precipitation during strong El Niño events are better explained using the ENSO Longitude Index (ELI), which captures the diversity of ENSO’s spatial patterns in a single metric, compared to the traditional Niño3.4 index, which measures SST anomalies in a fixed region and therefore fails to capture ENSO diversity. The physically-based ELI better explains western US precipitation variability because it tracks the zonal shifts in tropical Pacific deep convection that drive teleconnections through the response in the extratropical wave-train, integrated vapor transport, and atmospheric rivers. This research provides evidence that ELI improves the value of ENSO as a predictor of California’s seasonal hydroclimate extremes compared to traditional ENSO indices, especially during strong El Niño events.