Improved Imaging of the Large-Scale Structure of a Groundwater System with Airborne Electromagnetic Data

American Geophysical Union (AGU) | March 17th, 2022

A groundwater model is a representation of a groundwater system used to both understand the properties and processes of the subsurface, and to manage the groundwater reso

A groundwater model is a representation of a groundwater system used to both understand the properties and processes of the subsurface, and to manage the groundwater resource. An important step in developing a groundwater model is describing the large-scale structure, the "plumbing system" that controls the groundwater flow. Given the size of many groundwater models, obtaining an accurate description of the large-scale structure can be a challenging task. The traditional approach has involved the drilling of wells. While wells can provide accurate information at the location of the wells, the spatial sampling of the subsurface that can be accomplished through the drilling of wells is limited. An airborne electromagnetic (AEM) method provides an alternative by using a geophysical measurement to map out the electrical resistivity to depths of hundreds of meters. Working with AEM data acquired in the Kaweah Subbasin in the Central Valley of California, we were able to image the large-scale structure - the bedrock surface and a thick clay layer. The key improvement was made by incorporating prior knowledge into the inversion of the data. Once we had obtained the large-scale structure, we found that this could be used to improve the imaging of the smaller-scale structure.

Inaction’s Economic Cost for California’s Water Supply Challenges

University of California, Davis (UC Davis) | May 14th, 2025

California’s water system is in for challenges in coming decades as climate, groundwater policy, and environmental regulations reduce availability and increase variabil

California’s water system is in for challenges in coming decades as climate, groundwater policy, and environmental regulations reduce availability and increase variability in water supplies for agricultural and urban uses. A previous report estimated 4 to 9 million acre-feet (maf) per year of unavoidable reductions in existing water supplies, 12% to 25% of today’s water use (Lund et al. 2024). This report estimates the economic costs of not responding to these reductions in water availability.

Increased drought and extreme events over continental United States under high emissions scenario

Nature Portfolio (Springer Nature) | December 6th, 2023

Increased flood exposure due to climate change and population growth in the United States

American Geophysical Union (AGU) | October 30th, 2021

Precipitation extremes are increasing globally due to anthropogenic climate change. However, there remains uncertainty regarding impacts upon flood occurrence and subseq

Precipitation extremes are increasing globally due to anthropogenic climate change. However, there remains uncertainty regarding impacts upon flood occurrence and subsequent population exposure. Here, we quantify changes in population exposure to flood hazard across the contiguous United States. We combine simulations from a climate model large ensemble and a high‐resolution hydrodynamic flood model—allowing us to directly assess changes across a wide range of extreme precipitation magnitudes and accumulation timescales. We report a mean increase in the 100‐year precipitation event of ~20% (magnitude) and >200% (frequency) in a high warming scenario, yielding a ~30–127% increase in population exposure. We further find a nonlinear increase for the most intense precipitation events—suggesting accelerating societal impacts from historically rare or unprecedented precipitation events in the 21st century.

Increasing importance of 2021 temperature as a driver of streamflow drought spatial extent

Environmental Research Letters (IOP) | February 9th, 2021

Widespread streamflow droughts can pose substantially greater societal challenges than spatially less extensive events because of the complex realities of trans-regional

Widespread streamflow droughts can pose substantially greater societal challenges than spatially less extensive events because of the complex realities of trans-regional water management. In a warming climate, drought spatial extent may change along with changes in underlying hydro-meteorological contributors. Here, we assess changes in streamflow drought spatial extent over the period 1981–2018 across the conterminous United States, and how the importance of potential hydro-meteorological contributors has changed over time. We first derive a monthly time series of drought spatial extent and look at trends in streamflow drought spatial extent. We then determine the spatial percentage 'overlap' of precipitation droughts, temperature anomalies, snow-water-equivalent deficits, and soil moisture deficits with the area under streamflow drought to look at the changing influence of these contributors on spatial extent. Our results show that (1) the spatial extent of droughts has increased, mainly because of increases in the extent of small droughts; (2) streamflow drought extents overall substantially overlap with soil moisture deficits and the relationship of drought to precipitation and temperature anomalies varies seasonally; and (3) the importance of temperature as a contributor to drought extent has increased over time. We therefore conclude that continued global warming may further increase drought extents, requiring adaptation of regional drought management strategies.

Indicators of Climate Change in California

California Environmental Protection Agency (CalEPA) | May 16th, 2018

From record temperatures to proliferating wildfires and rising seas, climate change poses an immediate and escalating threat to California’s environment, public health,

From record temperatures to proliferating wildfires and rising seas, climate change poses an immediate and escalating threat to California’s environment, public health, and economic vitality. Recent climate-related events – such as the devastating 2017 wildfires and the record-setting 2012-16 drought – have highlighted the challenges that confront the state as its climate continues to evolve.  California has been a pioneer in addressing climate change. This report helps support policy decisions and facilitates communication about climate change by providing, in a single document, indicators characterizing its multiple aspects in California.  Indicators are scientifically-based measurements that track trends in various aspects of climate change. Many indicators reveal discernable evidence that climate change is occurring in California and is having significant, measurable impacts in the state.  The report’s 36 indicators are grouped into four categories, as listed below. The report discusses what these indicators show, why they are important, and the factors that may be influencing them.  * Human-influenced (anthropogenic) drivers of climate change, such as greenhouse gas emissions * Changes in the state’s climate * Impacts of climate change on physical systems, such as oceans, lakes and snowpack * Impacts of climate change on biological systems – humans, vegetation and wildlife

Inflation Reduction Act of 2022

United States Congress | August 6th, 2022

Click "get document" for the entire bill. Scroll below to see its drought relief amendment.

Click "get document" for the entire bill. Scroll below to see its drought relief amendment.

Integrated Coastal Groundwater Monitoring Program and Plan

Monterey County Water Resources Agency (MCWRA) | May 19th, 2019

California American Water Company (CalAm) is working to increase sustainability of their water supply portfolio to meet the long-term needs of customers in their

California American Water Company (CalAm) is working to increase sustainability of their water supply portfolio to meet the long-term needs of customers in their service area on the Monterey Peninsula. Accordingly, CalAm has proposed the Monterey Peninsula Water Supply Project (MPWSP). The MPWSP includes a desalination plant, distribution pipelines, aquifer storage and recovery and in-lieu use of desalinated water. Feedwater for the desalination plant would be from a seawater intake system consisting of slant wells constructed into the shallow aquifers at the coastal margin of the Salinas Valley Groundwater Basin (SVGB). The objective of the MPWSP is to meet CalAm’s long-term water demands and comply with state imposed regulatory requirements1. A MPWSP Test Slant Wells Study (HWG, 2017) was conducted to evaluate project effects and support preparation of a draft and Final Environmental Impact Statement/Environmental Impact Report (EIR/EIS) (ESA, 2017). CalAm has received a Certificate of Public Convenience and Necessity CPCN) for the MPWSP from the California Public Utilities Commission (CPUC)2. The EIR/EIS supported the CPUC decision. This document presents a proposed Coastal Monitoring Plan (Monitoring Plan) to continue observing the MPWSP effects, if any, on the SVGB.

Integrated Water Availability in the Conterminous United States, 2010–20, Chapter F of U.S. Geological Survey Integrated Water Availability Assessment—2010–20

U.S. Geological Survey (USGS) | January 15th, 2025

The following are the key points of this chapter:  At the national scale, water supply is much higher than human demand, but regions with lower water supply show sm

The following are the key points of this chapter:  At the national scale, water supply is much higher than human demand, but regions with lower water supply show smaller differences and greater potential for imbalances in supply relative to demand. Eight percent of the conterminous United States (CONUS) population (26.7 million people) live in areas with chronic stress from water-supply and use imbalances. The Southern High Plains, Texas, Central High Plains, and Mississippi Embayment hydrologic regions had the most widespread coverage of 12 digit hydrologic unit code (HUC12) watersheds with water stress from supply-use limitations. Several fish species of conservation concern have large proportions of their habitat range in areas with chronic imbalances between surface-water supply and human use. Streams with elevated nutrient concentrations greater than reference conditions were widespread across the CONUS. Limitation of ecological water availability occurred even in humid areas of the CONUS without water-supply and use imbalances, primarily because of flow alterations associated with urban areas, other land uses, and water-management and infrastructure. The California–Nevada, Southwest Desert, Central High Plains, Southern High Plains, Texas, Mississippi Embayment, and Florida hydrologic regions showed high or severe stress in multiple aspects of water availability. A high proportion of the population living in areas with water-availability limitations are considered to be socially vulnerable, although this is a small percentage of the total CONUS population. Companion chapters: U.S. Geological Survey Integrated Water Availability Assessment—2010–20, Chapter A Water Supply in the Conterminous United States, Alaska, Hawaii, and Puerto Rico, Water Years 2010–20, Chapter B Status of Water-Quality Conditions in the United States, 2010–20, Chapter C  Water Use Across the Conterminous United States, Water Years 2010–20, Chapter D  Climate Change and Future Water Availability in the United States, Chapter E   

Inter-Basin Transfers Extend the Benefits of Water From Forests to Population Centers Across the Conterminous U.S.

American Geophysical Union (AGU) | May 12th, 2022

Clean water from forests is commonly used to supply drinking water to communities both within and outside basin boundaries through inter-basin transfers (IBTs). Here, we

Clean water from forests is commonly used to supply drinking water to communities both within and outside basin boundaries through inter-basin transfers (IBTs). Here, we modified the Water Supply Stress Index (WaSSI) model to provide estimates of mean water yield and the proportion of mean flow originating on forested lands at the 12-Digit Hydrologic Unit Code scale across the conterminous United States (CONUS). We accounted for the benefits of forests for drinking water supply and receiving populations through IBTs by incorporating a new IBT database, surface intake location information for public drinking water systems, and modeled water yield from forests. We compiled the new database of 594 IBTs ranging from 0.01 million m3 yr−1 to 8,900 million m3 yr−1, for a total transferred volume of 116,894 million m3 yr−1. According to our results, forested lands comprised 28.7% of the total land area across CONUS, but contributed 46% of the total surface water yield. Approximately 125.5 million people derived more than 10% of their surface drinking water supply from forested lands, and 83.1 million people received more than 50% of their surface drinking water supply from forested lands. Of those 83.1 million people receiving more than 50% of their surface drinking water supply from forested lands, 19.4 million people obtained some (≥0.01%) of that water through IBTs. We conclude that accounting for IBTs is critical to accurately assess the contribution of forested watersheds for surface drinking water supply. Hydrologic models for assessment and decision making must include IBTs to fully account for the effects of climate change and human population dynamics on water resource availability at watershed to regional scales. Results from this study can aid water resource and forest managers in developing integrated watershed management plans at a time when climate change, population growth, and land use change threaten water supplies.