Airborne Geophysical Method Images Fast Paths for Managed Recharge of California’s Groundwater

Environmental Research Letters (IOP) | November 17th, 2022

Given the substantial groundwater level declines in the Central Valley of California, there is an urgent need to supplement the recharge of the groundwater systems by imp

Given the substantial groundwater level declines in the Central Valley of California, there is an urgent need to supplement the recharge of the groundwater systems by implementing managed aquifer recharge. With approximately 170 km3 (140 million acre-feet) of available groundwater storage space, water deemed to be excess during wet years could be spread on the ground surface at selected locations allowing it to move downward to recharge the underlying aquifer system. Along the eastern edge of the Central Valley there are large paleovalleys that can act as fast paths expediting the downward movement of water. These paleovalleys, incised and then filled with coarse-grained materials – sand, gravel, cobbles – at the end of the last glacial period, are referred to as incised valley fill (IVF) deposits. An IVF deposit has been mapped at one location in the Kings River alluvial fan, with others proposed to exist in the fans of major rivers. If located, these deposits would be optimal sites for managed recharge. In this study, we assessed the use of a helicopter-deployed geophysical method to efficiently locate IVF deposits throughout the Central Valley. We acquired 542 line-kilometers of airborne electromagnetic (AEM) data in the Kings River alluvial fan, with dense line-spacing over the Kings River IVF deposit which had been mapped as ~2 km wide, extending over 20 km into the Central Valley, from the ground surface to a depth of 30 m. The IVF deposit was unambiguously imaged in the AEM data as an extensive linear feature that was more electrically resistive than the surrounding materials due to the high percentage of coarse-grained sediments. This study provides the evidence to support the rapid adoption of the AEM method to locate IVF deposits along the eastern edge of the Central Valley. These deposits provide valuable natural infrastructure for recharging California’s groundwater.

Aliso Water District Groundwater Sustainability Plan

Aliso Water District Groundwater Sustainability Agency | January 17th, 2020

Aliso Water District Groundwater Sustainability Plan (Amended)

Aliso Water District Groundwater Sustainability Agency | July 7th, 2022

The January 2020 AWD GSA GSP, along with the other GSPs of the Delta-Mendota Subbasin, was deemed incomplete by DWR January 21, 2022 (Appendix H). The incomplete determin

The January 2020 AWD GSA GSP, along with the other GSPs of the Delta-Mendota Subbasin, was deemed incomplete by DWR January 21, 2022 (Appendix H). The incomplete determination provided 180 days to respond to the deficiencies identified by DWR. Subsequently, multiple consultations with DWR and meetings of the Delta-Mendota GSP groups were held to develop a coordinated response. This GSP, including the Common Chapter (Appendix B), addresses the concerns of DWR’s January 2022 Determination Letter. Due to size, this file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5

Alternative management paradigms for the future of the Colorado and Green Rivers

U.S. Department of Agriculture (USDA) | January 28th, 2021

The Colorado River is among the most extensively managed river systems in the world. The river’s headwaters are within the Rocky Mountains in the United States. From t

The Colorado River is among the most extensively managed river systems in the world. The river’s headwaters are within the Rocky Mountains in the United States. From there, it flows through the arid lands of the Colorado Plateau and the Basin-and-Range to its delta in northwestern Mexico. Here, the river is the only significant water supply in an otherwise starkly arid landscape and has long been called “America’s Nile.” It provides a critical water supply for nearly four million acres of irrigated land, municipal supplies for 30 million people located within and outside the basin, and more than 4,200 MW of hydropower generation capacity. The Colorado River and some of its tributaries also provide an existing or potential water supply for at least 15 Native American tribes. The river flows through seven National Wildlife Refuges, four National Recreation Areas, and five National Parks. Today, the annual consumptive uses and losses of streamflow in the basin typically exceed the amount of water available, and the river rarely flows into the Gulf of California. The impacts of climate change are likely to decrease future runoff and intensify droughts, thereby threatening current and future uses in the basin. Clearly, new ways of thinking about and managing the river need to be sought and implemented.

Alternatives Report Post-2026 Operational Guidelines and Strategies for Lake Powell and Lake Mead

U.S. Bureau of Reclamation (USBR) | January 17th, 2025

In December 2007 the Secretary of the Interior adopted coordinated operating guidelines for operation of Glen Canyon Dam and Hoover Dam for an interim period that expires

In December 2007 the Secretary of the Interior adopted coordinated operating guidelines for operation of Glen Canyon Dam and Hoover Dam for an interim period that expires in 2026. To address long-term Colorado River operations after the expiration of these guidelines, the United States Department of the Interior initiated a National Environmental Policy Act process on June 16, 2023, to develop and adopt successor domestic guidelines and agreements for the operation of Glen Canyon Dam and Hoover Dam to take effect in mid-2026, before the current operational framework expires. On November 20, 2024, the Bureau of Reclamation published the range of alternatives planned for analysis in the draft environmental impact statement and committed to providing additional information in a subsequent report. This report describes these alternatives and the process for developing them in more detail. The alternatives were developed over the past year and incorporate considerable input received from the Colorado River Basin States, Colorado River Basin Tribes, conservation organizations, other federal agencies, and other stakeholders during that time. Throughout 2024, the Bureau of Reclamation worked extensively with these key partners to integrate their input into the range of alternatives. The alternatives identified in this report provide a reasonable and broad range of Colorado River operations that capture an appropriate range of potential environmental impacts from implementing new operational guidelines post-2026. Click here for USBR notes on the alternatives development process.

Amended Groundwater Sustainability Plan, Tri-County Water Authority - Tule Subbasin

Tri-County Water Authority | July 27th, 2022

The Tule Subbasin submitted six GSPs, including one for the Tri-County Water Authority, in January 2020 to the Department of Water Resources (DWR). DWR was required to de

The Tule Subbasin submitted six GSPs, including one for the Tri-County Water Authority, in January 2020 to the Department of Water Resources (DWR). DWR was required to determine whether the GSPs conformed to the specific requirements of SGMA. DWR issued a single determination letter for the Tule Subbasin commenting on all six GSPs. In a letter dated January 28, 2022, DWR determined that that the GSP is incomplete. DWR stated that the GSP was considered incomplete as “it does not define undesirable results or set sustainable management criteria for groundwater levels, subsidence, and water quality in the manner consistent with SGMA and the GSP regulations.” Upon receiving the incomplete determination, the Subbasin had 180 days to address the identified deficiencies and submit revised GSPs by July 27, 2022. The TCWA is submitting this 2022 Amended GSP to address the three deficiencies outlined in the determination letter. Due to size, this file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9

Amended Olcese Groundwater Sustainability Plan (GSP) for Certain Lands Overlying the Kern County Subbasin

Olcese Groundwater Sustainability Agency | July 27th, 2022

This GSP has been prepared by the Olcese GSA, which is the GSA for the portion of the Kern County Subbasin of the San Joaquin Valley Groundwater Basin (Department of Wate

This GSP has been prepared by the Olcese GSA, which is the GSA for the portion of the Kern County Subbasin of the San Joaquin Valley Groundwater Basin (Department of Water Resources [DWR] Basin No. 5-022.14, referred to herein as the “Kern Subbasin” or “Basin”) that underlies the Olcese Water District (“OWD” or “District”). The area that is covered by this GSP is referred to herein as the “Olcese Groundwater Sustainability Agency Area” or “Olcese GSA Area” and is located in the eastern portion of the Kern Subbasin. The Kern Subbasin is one of 21 basins and subbasins identified by the DWR as being critically overdrafted, a designation that triggers an accelerated timetable for GSP development by 2020 and achievement of sustainability by 2040. As of June 2022, a total of 14 GSAs, including the Olcese GSA, have been formed within the Kern Subbasin and a total of six GSPs have been prepared by these various GSAs. This Olcese GSP has been developed in coordination with the other GSPs for the Kern Subbasin to meet SGMA regulatory requirements1 while reflecting the unique hydrogeologic conditions within the Olcese GSA Area and preserving local control over water resources. Pursuant to the SGMA GSP submittal deadline, the Olcese GSP was originally submitted to DWR in January 2020; this amended Olcese GSP is in response to DWR’s 28 January 2022 letter entitled Incomplete Determination of the 2020 Groundwater Sustainability Plans Submitted for the San Joaquin Valley – Kern County Subbasin. Together, the Kern Subbasin GSPs provide a path to maintain the long-term sustainability of locally managed groundwater resources now and into the future. Due to size, this file has been divided. Part 1, Part 2

American River Group (ARG) Annual Report of Activities

Delta Stewardship Council (Delta Council) | November 14th, 2018

Amplified impacts of multi-year La Niñas on soil moisture compared to single-year La Niñas

Nature Portfolio (Springer Nature) | August 14th, 2025

This study examines December-January-February (DJF) soil moisture responses to multi-year (MY) and single-year (SY) La Niñas using a 2200-year CESM1 simulation, AGCM exp

This study examines December-January-February (DJF) soil moisture responses to multi-year (MY) and single-year (SY) La Niñas using a 2200-year CESM1 simulation, AGCM experiments, and observational data. Four regions where MY La Niñas amplify SY La Niñas’ impacts on soil moisture were identified: North America, Australia, the Middle East, and the Sahel. SY La Niñas typically cause soil moisture drying in the Middle East and North America and wetting in Australia and the Sahel. MY La Niñas enhance these effects in the second DJF due to the strengthening of precipitation anomalies or the accumulation of precipitation-induced soil moisture anomalies, except in the Sahel where wetting is driven in part by evapotranspiration anomalies. Soil moisture variations are linked to La Niña-induced sea surface temperature changes in the Indian Ocean (for Australia and the Middle East) and the Pacific Ocean (for North America). These amplified effects are largely supported by the observed MY La Niña events from 1948 to 2022. These findings emphasize the need to integrate MY La Niñas into regional agriculture and water resource management strategies to better anticipate and mitigate their impacts.

An Assessment of Urban Water Demand Forecasts in California

Pacific Institute | August 5th, 2020

In California, urban per capita water demand has declined dramatically over the past several decades, driven in part by greater uptake of water-efficient devices. These r

In California, urban per capita water demand has declined dramatically over the past several decades, driven in part by greater uptake of water-efficient devices. These reductions have important implications for estimating future water demand. However, failure to account for the long-term trend of declining per capita water demand has led to routine overestimation of future water demand. This can lead to unnecessary and costly investment in unneeded infrastructure and new sources of supply, higher costs, and adverse environmental impacts. This report examines the accuracy of long-range water demand forecasts for California’s 10 largest urban water suppliers. It finds that per capita water demand declined for all water suppliers between 2000 and 2015. In most cases, reductions in per capita water demand were so large that total water demand declined during this period. Additionally, all water suppliers overestimated demand, driven largely by inflated estimates of per capita water demand and, to a lesser extent, overestimates of population growth rates. The report offers recommendations on how to improve the accuracy of long-range water demand forecasts.