Replenishing Groundwater in the San Joaquin Valley

Public Policy Institute of California (PPIC) | April 1st, 2018

The San Joaquin Valley—which has the biggest imbalance between groundwater pumping and replenishment in the state—is ground zero for implementing the 2014 Sustainable

The San Joaquin Valley—which has the biggest imbalance between groundwater pumping and replenishment in the state—is ground zero for implementing the 2014 Sustainable Groundwater Management Act (SGMA). Expanding groundwater recharge could help local water users bring their basins into balance and make a dent in the long-term deficit of nearly 2 million acre-feet per year. The experience with recharge in 2017?the first wet year since the enactment of SGMA?offers valuable insights in how to expand recharge. A survey of valley water districts’ current recharge efforts revealed strong interest in the practice, and a number of constraints. The following actions are needed to better capitalize on future opportunities: Clarify rules on water available for recharge. The State Water Board needs to develop an expeditious process for enabling water users to capture surface water when it is available. Beyond the legal aspects of establishing rights for diversion and storage, an essential part of this process is technical: developing a simple, rapid way to determine when river flows exceed water required for environmental purposes and downstream users. Evaluate infrastructure capacity. One of the key challenges for expanding recharge is that most available flows are in the northern part of the valley, while most of the overdraft?and best recharge lands?are in the south. In addition, these flows are mainly available for just a few months. A top priority is to evaluate opportunities for improving the use of existing infrastructure (conveyance facilities, surface reservoirs, and recharge basins) and determine where additional investments are warranted. A big bottleneck is likely to be regional conveyance, which is inadequate for capturing and moving high flows to suitable recharge locations. Improve recharge on farmland. Active recharge on farmland may be one of the most promising ways to capture water cost-effectively in wetter years, but it is low relative to its potential. Significantly ramping up this practice will require addressing a suite of technical issues and establishing incentives. Address regulatory barriers. State and federal agencies need to improve processes for approving construction of new recharge projects, moving recharge water through their conveyance facilities, and enabling more flexibility in where water is stored. Water managers and growers also need guidelines from the state for implementing on-farm recharge in ways that are consistent with water quality rules. Strengthen groundwater accounting. Better accounting of water going into and out of groundwater basins is key to sustainable management. It is also needed for developing incentives for growers to recharge, encouraging recharge partnerships, and informing decisions on new investments. Making the most of recharge opportunities will require high levels of cooperation among a wide variety of stakeholders. Local and regional partnerships?for capturing and moving water efficiently, making new investments, and devising projects that bring multiple benefits?are key to helping the region manage this critical resource over the long-term.

Report of Waste Discharge and Technical Report

Westlands Water District | July 10th, 2019

This Technical Report is in support of a Report of Waste Discharge (ROWD) for an agricultural aquifer storage and recovery (Ag-ASR) program for Westlands Water District

This Technical Report is in support of a Report of Waste Discharge (ROWD) for an agricultural aquifer storage and recovery (Ag-ASR) program for Westlands Water District (Westlands or District). The District is located in western Fresno and Kings Counties in the San Joaquin Valley. With the new Sustainable Groundwater Management Act (SGMA) signed into law in 2014, Westlands is pursuing means to recharge groundwater within the District’s boundaries, which coincide with the Westside Subbasin (Groundwater Subbasin Number 5-22.09). Due to the presence of poor quality shallow groundwater, fine-grained soils, and the Corcoran Clay restrictive layer, surface recharge opportunities are limited (Schmidt, 2009). Direct injection using Ag-ASR wells holds promise as a more widely implementable recharge method in the District.

Report on Feasibility of Feather River Project and Sacramento-San Joaquin Delta Diversion Projects Proposed as Features of the California Water Plan

California Department of Water Resources (DWR) | May 17th, 1951

Response of the upper ocean to northeast Pacific atmospheric rivers under climate change

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

Click here for a plain language summary from the National Center for Atmospheric Research

Click here for a plain language summary from the National Center for Atmospheric Research

Responses and impacts of atmospheric rivers to climate change

Nature Portfolio (Springer Nature) | March 9th, 2020

Atmospheric rivers (ARs) are characterized by intense moisture transport, which, on landfall, produce precipitation which can be both beneficial and destructive. ARs in C

Atmospheric rivers (ARs) are characterized by intense moisture transport, which, on landfall, produce precipitation which can be both beneficial and destructive. ARs in California, for example, are known to have ended drought conditions but also to have caused substantial socio-economic damage from landslides and flooding linked to extreme precipitation. Understanding how AR characteristics will respond to a warming climate is, therefore, vital to the resilience of communities affected by them, such as the western USA, Europe, East Asia and South Africa. In this Review, we use a theoretical framework to synthesize understanding of the dynamic and thermodynamic responses of ARs to anthropogenic warming and connect them to observed and projected changes and impacts revealed by observations and complex models. Evidence suggests that increased atmospheric moisture (governed by Clausius–Clapeyron scaling) will enhance the intensity of AR-related precipitation — and related hydrological extremes — but with changes that are ultimately linked to topographic barriers. However, due to their dependency on both weather and climate-scale processes, which themselves are often poorly constrained, projections are uncertain. To build confidence and improve resilience, future work must focus efforts on characterizing the multiscale development of ARs and in obtaining observations from understudied regions, including the West Pacific, South Pacific and South Atlantic.

Review of Science Used to Estimate Water Supply Reliability Involving the Delta

Delta Stewardship Council (Delta Council) | April 3rd, 2018

Review of the Long-Term Operations of the Central Valley Project and the State Water Project

National Academy of Sciences (NAS) | November 10th, 2025

The CVP and SWP (referred to collectively as “the Projects”) rarely deliver their full contracted  amount of water. Some of this is inherent in the operation of larg

The CVP and SWP (referred to collectively as “the Projects”) rarely deliver their full contracted  amount of water. Some of this is inherent in the operation of large water projects with diverse demands in a dry and highly variable climate. A growing, complex regulatory environment of state and federal laws, some of which were created to protect fish species endemic to the Delta, has further restricted CVP and SWP operations.  These fish include the southern distinct population segment of North American green sturgeon, California Central Valley steelhead, Central Valley spring-run Chinook salmon, Sacramento River winter-run Chinook salmon, longfin smelt, and Delta smelt. Operating the Projects while trying to prevent species extinction can be a source of conflict if the actions to prevent extinction reduce the amount of water that can be exported. Project operation into the future will likely become more challenging as changes in various climatic factors push the listed species closer to their thresholds of survivability. Hence, in late 2023 USBR contracted with the National Academies of Sciences, Engineering, and Medicine (NASEM) to form an expert committee that could serve as an independent review for the CVP and SWP as they operate into the future. The Committee’s statement of task appears in Box S-1. The three actions chosen for the study—the Shasta Coldwater Pool Management Action, the Old and Middle River Flow Management Action, and the Summer-Fall Habitat Action for Delta Smelt— are perceived as consequential for species survival and controversial for their effects on water deliveries to contractors.

Review of Water Supply Reliability Estimation Related to the Sacramento-San Joaquin Delta

Delta Stewardship Council (Delta Council) | June 16th, 2022

Ridging associated with drought in western and southwestern United States: characteristics, trends and predictability

American Meteorological Society (AMS) | April 1st, 2020

Persistent winter ridging events are a consistent feature of meteorological drought across the western and southwestern United States. In this study, a ridge detection al

Persistent winter ridging events are a consistent feature of meteorological drought across the western and southwestern United States. In this study, a ridge detection algorithm is developed and applied on daily geopotential height anomalies to track and quantify the diversity of individual ridge characteristics (e.g., position, frequency, magnitude, extent, and persistence). Three dominant ridge types are shown to play important, but differing, roles for influencing the location of landfalling atmospheric rivers (ARs), precipitation, and subsequently meteorological drought. For California, a combination of these ridge types is important for influencing precipitation deficits on daily through seasonal time scales, indicating the various pathways by which ridging can induce drought. Furthermore, both the frequency of ridge types and reduced AR activity are necessary features for explaining drought variability on seasonal time scales across the western and southwestern regions. The three ridge types are found to be associated in different ways with various remote drivers and modes of variability, highlighting possible sources of subseasonal-to-seasonal (S2S) predictability. A comparison between ridge types shows that anomalously large and persistent ridging events relate to different Rossby wave trains across the Pacific with different preferential upstream locations of tropical heating. For the “South-ridge” type, centered over the Southwest, a positive trend is found in both the frequency and persistence of these events across recent decades, likely contributing to observed regional drying. These results illustrate the utility of feature tracking for characterizing a wider range of ridging features that collectively influence precipitation deficits and drought.

Risk-Informed Future Climate Scenario Development for the State Water Project Delivery Capability Report

California Department of Water Resources (DWR) | August 24th, 2023

This report introduces and documents an extensive effort undertaken by the California Department of Water Resources (DWR) to develop risk-informed future climate scenario

This report introduces and documents an extensive effort undertaken by the California Department of Water Resources (DWR) to develop risk-informed future climate scenarios for the State Water Project (SWP) Delivery Capability Report (DCR), a report issued by the SWP every two years. These reports present DWR’s analysis of the SWP system and planning information for users of SWP water. The analysis provides information about how climate change, regulatory, and operational considerations affect SWP delivery capability. Specifically, the report must provide “…under a range of hydrologic conditions, the then existing overall delivery capability of the project facilities and the allocation of that capacity to each contractor. The range of hydrologic conditions shall include the historic extended dry cycle and long-term average.” (Settlement Agreement 2003).