San Joaquin River

Characterization of Groundwater Recharge and Flow in California's San Joaquin Valley From InSAR-Observed Surface Deformation

American Geophysical Union (AGU) | March 4th, 2021

Surface deformation in California's Central Valley (CV) has long been linked to changes in groundwater storage. Recent advances in remote sensing have enabled the mappin

Surface deformation in California's Central Valley (CV) has long been linked to changes in groundwater storage. Recent advances in remote sensing have enabled the mapping of CV deformation and associated changes in groundwater resources at increasingly higher spatiotemporal resolution. Here, we use interferometric synthetic aperture radar (InSAR) from the Sentinel-1 missions, augmented by continuous Global Positioning System (cGPS) positioning, to characterize the surface deformation of the San Joaquin Valley (SJV, southern two-thirds of the CV) for consecutive dry (2016) and wet (2017) water years. We separate trends and seasonal oscillations in deformation time series and interpret them in the context of surface and groundwater hydrology. We find that subsidence rates in 2016 (mean −42.0 mm/yr; peak −345 mm/yr) are twice that in 2017 (mean −20.4 mm/yr; peak −177 mm/yr), consistent with increased groundwater pumping in 2016 to offset the loss of surface-water deliveries. Locations of greatest subsidence migrated outwards from the valley axis in the wetter 2017 water year, possibly reflecting a surplus of surface-water supplies in the lowest portions of the SJV. Patterns in the amplitude of seasonal deformation and the timing of peak seasonal uplift reveal entry points and potential pathways for groundwater recharge into the SJV and subsequent groundwater flow within the aquifer. This study provides novel insight into the SJV aquifer system that can be used to constrain groundwater flow and subsidence models, which has relevance to groundwater management in the context of California's 2014 Sustainable Groundwater Management Act (SGMA).

Characterizing and quantifying nutrient sources, sinks and transformations in the Delta: synthesis, modeling, and recommendations for monitoring

San Francisco Estuary Institute (SFEI) | January 5th, 2016

The Sacramento-San Joaquin Delta (the Delta) receives high loads of the nutrients nitrogen (N) and phosphorous (P) from wastewater treatment effluent and agricultural run

The Sacramento-San Joaquin Delta (the Delta) receives high loads of the nutrients nitrogen (N) and phosphorous (P) from wastewater treatment effluent and agricultural runoff. Flows from the Sacramento River, San Joaquin River, and other tributaries transport these loads through a complex network of rivers, channels and flooded islands, before entering San Francisco Bay. Excessive loads of N and P can adversely impact ecosystem health by causing excessive algal blooms and low dissolved (Valiela et al, 1992; Kamer and Stein 2003). Excessive nutrients may also contribute to the occurrence of harmful algal blooms (Bates et al, 1989) and overgrowth of nuisance aquatic macrophytes (Valiela et al, 1992). Major nutrient management decisions are being considered in both the Delta and San Francisco Bay, and those decisions require the best-available science to understand the factors that regulate ambient conditions, and the effects of loads and ambient conditions on ecosystem health. A mechanistic and quantitative understanding of nutrient cycling and fate in the Delta is essential both for informed decisions related to current conditions and also because of major anticipated changes in both loads to the Delta (upgrades at wastewater treatment facilities) and habitat function due to restoration efforts and water management. We hypothesized that the Delta is an important biogeochemical reactor, and that transformations or losses strongly regulate ambient nutrient concentrations within the Delta and modulate nutrient loads to San Francisco Bay. Both N and P have complex cycles and require careful investigation. In this paper, we focus on nitrogen, including loads, cycling, and losses or transformations that influence its ultimate fate.

Characterizing pyrethroid and fipronil concentrations in biosolids

Science of the Total Environment (Elsevier) | February 28th, 2025

Pesticides are prevalent in wastewater, yet few studies have measured pesticides in biosolids and aqueous media from samples collected concurrently. Seventeen California

Pesticides are prevalent in wastewater, yet few studies have measured pesticides in biosolids and aqueous media from samples collected concurrently. Seventeen California wastewater treatment plants (WWTPs) were sampled in May 2020. Biosolids samples were analyzed for 27 analytes, and paired aqueous samples (influent and effluent) were analyzed for 23 analytes. Analytes included fipronil and its transformation products (fiproles), pyrethroids, novaluron, and several other pesticides with down-the-drain transport potential. Of the 27 compounds analyzed in biosolids samples, 16 were detected in at least one sample, and 10 had a detection frequency (DF) of at least 25 %. Fipronil sulfone, fipronil sulfide, and fipronil were the most frequently detected fiproles (DF = 100 %, 94 %, and 67 %, respectively); permethrin was the most frequently detected pyrethroid (DF = 100 %), followed by bifenthrin (DF = 94 %), cyhalothrin (DF = 89 %), and etofenprox (DF = 78 %). To elucidate fipronil transformation pathways within the treatment system, data from the three sample types were compared; findings were generally consistent with transformation pathways reported previously (e.g., some fiproles were rarely detected in influent or biosolids, but frequently detected in effluent, indicating their formation during the treatment process). No correlations were found between WWTP characteristics and pesticide concentrations in biosolids. The fraction of organic carbon (fOC) of each biosolids sample was measured, and a statistically significant negative correlation was observed between fOC and some fiproles, but not fipronil; possible explanations are discussed. Additional analysis for two major agricultural pesticides (bifenthrin and permethrin) indicated that estimated mass loads of these pesticides in biosolids applied to land as a soil amendment are minimal (approximately 2 to 3 orders of magnitude lower) compared to inputs from agricultural applications. This study provides insight on the magnitude of pesticides entering the environment via land-applied biosolids; existing regulations surrounding agricultural pesticide applications are expected to also be protective of the relatively low inputs from biosolids.

Chowchilla Subbasin Staff Assessment

California State Water Resources Control Board (SWRCB) | April 1st, 2025

The state intervention process for the Chowchilla Subbasin was triggered in March 2023 when DWR determined the subbasin’s 2022 GSP was inadequate and identified multipl

The state intervention process for the Chowchilla Subbasin was triggered in March 2023 when DWR determined the subbasin’s 2022 GSP was inadequate and identified multiple deficiencies in the GSP. DWR identified issues regarding the local agencies’ plans for managing for the chronic lowering of groundwater levels and land subsidence (land sinking due to groundwater pumping). State Water Board staff reviewed the 2022 GSP and determined that implementing the 2022 GSP would result in additional groundwater level declines, potential impacts to drinking water wells, and damage to subbasin infrastructure, such as canals and levees, through continued land subsidence. The GSAs released a revised draft GSP in August 2024, which they adopted with slight revisions in March 2025 (2025 GSP). State Water Board staff evaluated the 2025 GSP to determine if identified deficiencies were addressed. The GSAs made significant progress through the 2025 GSP and adequately addressed deficiencies. Through the 2025 GSP, the GSAs show a greater commitment to protecting drinking water users and improved groundwater management. State Water Board staff concludes the GSAs amended the GSP such that a probationary designation of the Chowchilla Subbasin is unnecessary and recommends the Board return the Subbasin to DWR’s jurisdiction for continued evaluation of local management under SGMA.

Chowchilla Subbasin Sustainable Groundwater Management Act (SGMA) Groundwater Sustainability Plan (3rd Revision)

Madera County | January 3rd, 2025

In 2024-2025, the GSAs revised the Subbasin GSP to:  Amend the Domestic Well Mitigation Program Refine the Groundwater Level Representative Monitoring Sites (RMS

In 2024-2025, the GSAs revised the Subbasin GSP to:  Amend the Domestic Well Mitigation Program Refine the Groundwater Level Representative Monitoring Sites (RMS) Network Refine Groundwater Level Sustainable Management Criteria (SMC)  Backstop Projects and Management Actions Refine Subsidence SMC and Provide for Subsidence Mitigation

Chowchilla Subbasin Sustainable Groundwater Management Act (SGMA) Groundwater Sustainability Plan (Revised)

Chowchilla Subbasin GSP Advisory Committee | July 27th, 2022

Due to file size, this document has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 12, Part 13, Part 14, Par

Due to file size, this document has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 12, Part 13, Part 14, Part 15, Part 16, Part 17  

Chowchilla Subbasin Sustainable Groundwater Management Act (SGMA) Groundwater Sustainablity Plan

Chowchilla Subbasin GSP Advisory Committee | January 1st, 2020

Civic Engagement and Water Data: How Can California Make Data Work for Decision Makers?

University of California, Berkeley (UC Berkeley) | September 1st, 2020

 Much attention is focused on water data in California, and for good reason. California is struggling to make decisions that adapt its water systems to pressures such as

 Much attention is focused on water data in California, and for good reason. California is struggling to make decisions that adapt its water systems to pressures such as climate change and population growth. Fully informed decisions are impossible without accurate and accessible data and information to support them. California already produces immense amounts of water-related data. However, agencies and stakeholders currently struggle to bring these data together to support routine decision making. Overall, we lack any systematic understanding of whether and how existing data can support the needs of decision makers. 

Classifying California’s stream thermal regimes for cold-water conservation

PLOS | August 20th, 2021

Stream temperature science and management is rapidly shifting from single-metric driven approaches to multi-metric, thermal regime characterizations of streamscapes. Giv

Stream temperature science and management is rapidly shifting from single-metric driven approaches to multi-metric, thermal regime characterizations of streamscapes. Given considerable investments in recovery of cold-water fisheries (e.g., Pacific salmon and other declining native species), understanding where cold water is likely to persist, and how coldwater thermal regimes vary, is critical for conservation. California’s unique position at the southern end of cold-water ecosystems in the northern hemisphere, variable geography and hydrology, and extensive flow regulation requires a systematic approach to thermal regime classification. We used publicly available, long-term (> 8 years) stream temperature data from 77 sites across California to model their thermal regimes, calculate three temperature metrics, and use the metrics to classify each regime with an agglomerative nesting algorithm. Then, we assessed the variation in each class and considered underlying physical or anthropogenic factors that could explain differences between classes. Finally, we considered how different classes might fit existing criteria for cool- or cold-water thermal regimes, and how those differences complicate efforts to manage stream temperature through regulation. Our results demonstrate that cool- and cold-water thermal regimes vary spatially across California. Several salient findings emerge from this study. Groundwater-dominated streams are a ubiquitous, but as yet, poorly explored class of thermal regimes. Further, flow regulation below dams imposes serial discontinuities, including artificial thermal regimes on downstream ecosystems. Finally, and contrary to what is often assumed, California reservoirs do not contain sufficient cold-water storage to replicate desirable, reach-scale thermal regimes. While barriers to cold-water conservation are considerable and the trajectory of cold-water species towards extinction is dire, protecting reaches that demonstrate resilience to climate warming remains worthwhile.

Climate Action Plan Phase 1 Greenhouse Gas Emissions Reduction Plan Update 2023

California Department of Water Resources (DWR) | March 22nd, 2024

DWR developed the Greenhouse Gas Emissions Reduction Plan Update 2023 (Update 2023) to review its GHG reductions since Update 2020 and to update strategies for further re

DWR developed the Greenhouse Gas Emissions Reduction Plan Update 2023 (Update 2023) to review its GHG reductions since Update 2020 and to update strategies for further reduction consistent with legislative changes, including the GHG emissions reduction targets established in SB 1020 (2022) and SB 1203 (2022). It also includes DWR’s new role in emergency energy generation. Since the 2012 Plan was adopted, California’s wholesale electricity market has also seen a significant increase in renewable resources. To reflect this change and to align with industry practice in emission reporting, Update 2023 incorporates updated emission factors to determine emissions from unspecified market resources.