"Incomplete” Determination of the 2020 Groundwater Sustainability Plans Submitted for the San Joaquin Valley – Madera Subbasin

California Department of Water Resources (DWR) | September 22nd, 2022

The Department of Water Resources (Department) has evaluated the four groundwater sustainability plans (GSPs) submitted for the San Joaquin Valley – Madera Subbasin (Su

The Department of Water Resources (Department) has evaluated the four groundwater sustainability plans (GSPs) submitted for the San Joaquin Valley – Madera Subbasin (Subbasin), as well as the materials considered to be part of the required coordination agreement. Collectively, the four GSPs and the coordination agreement are referred to as the Plan for the Subbasin. The Department has determined that the Plan is “incomplete” pursuant to Section 355.2(e)(2) of the GSP Regulations. The Department based its incomplete determination on recommendations from the Staff Report, included as an enclosure to the attached Statement of Findings, which describes that the Subbasin’s Plan does not satisfy the objectives of the Sustainable Groundwater Management Act (SGMA) nor substantially comply with the GSP Regulations. The Staff Report also provides corrective actions which the Department recommends the Subbasin’s 7 groundwater sustainability agencies (GSAs) review while determining how and whether to address the deficiencies in a coordinated manner. The Subbasin’s GSAs have 180 days, the maximum allowed by the GSP Regulations, to address the identified deficiencies. Where addressing the deficiencies requires modification of the Plan, the GSAs must adopt those modifications into their respective GSPs and all applicable coordination agreement materials, or otherwise demonstrate that those modifications are part of the Plan before resubmitting it to the Department for evaluation no later than March 21, 2023.

“Good Luck Fixing the Problem”: Small Low-Income Community Participation in Collaborative Groundwater Governance and Implications for Drinking Water Source Protection

Society and Natural Resources (Routledge) | June 10th, 2020

There is increasing interest in the potential of source water protection to address chronic challenges with small systems and rural drinking water provision. Such a plann

There is increasing interest in the potential of source water protection to address chronic challenges with small systems and rural drinking water provision. Such a planning and management approach to increasing safe drinking water access, however, will likely require leveraging multi-stakeholder collaborative governance venues to this effect. This paper investigates the prospects of doing so using the case of California’s groundwater reform process known as the Sustainable Groundwater Management Act or SGMA. Interviews with drinking water stakeholders from small low-income communities in the San Joaquin Valley show how existing power and resource disparities limit the prospects of integrating rural drinking water priorities into regional planning. Long-term, more fundamental changes will be needed to meaningfully transform water management in this direction. Short-term state intervention is needed to protect equity and public good goals, raising potential contradictions between devolved water management and improved drinking water access that need to be addressed.

2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps

Monterey County Water Resources Agency (MCWRA) | April 24th, 2018

2017 SGMA Annual Report South American Subbasin (5-021.65) Sacramento Central Groundwater Authority

Sacramento Central Groundwater Authority | April 1st, 2018

The Sacramento Central Groundwater Authority (SCGA) has prepared an Annual Report describing groundwater conditions in the South American Subbasin for the 2017

The Sacramento Central Groundwater Authority (SCGA) has prepared an Annual Report describing groundwater conditions in the South American Subbasin for the 2017 Water Year (i.e., inclusive of months October 2016 to September 2017) in support of their pending Alternative Submittal. The Annual Report is intended for conveying monitoring and water use data to the State DWR on an annual basis to gauge performance of the groundwater subbasin relative to the sustainability goal set forth in a Groundwater Sustainability Plan (GSP) or, for SCGA, the Alternative Submittal. As such, SCGA is including sufficient information to provide interested parties with sufficient background and supporting details to serve as a public communications document for subbasin management and to take the place of historic biennial reporting available on the SCGA website.

2022-2023 Engineer’s Report on the Groundwater Conditions, Water Supply and Basin Utilization in the Orange County Water District

Orange County Water District (OCWD) | February 21st, 2024

Total water demands within Orange County Water District (OCWD) were 351,719 acre feet (AF) for the 2022-23 water year (beginning on July 1, 2022 and ending on June 30, 20

Total water demands within Orange County Water District (OCWD) were 351,719 acre feet (AF) for the 2022-23 water year (beginning on July 1, 2022 and ending on June 30, 2023). Groundwater production for the water year totaled 245,210 AF including any available In-Lieu Program water. The use of supplemental water in OCWD’s service area during the 2022-23 water year totaled 107,723 AF of which 88,441 AF resulted from the direct use by water agencies and districts and 19,282 AF were used for the purpose of groundwater basin replenishment and maintenance of seawater intrusion control barriers. For the water year which ended on June 30, 2023, the “annual overdraft” (annual basin storage decrease without supplemental replenishment water) was 52,250 AF. The accumulated overdraft decreased from 258,000 AF on June 30, 2022 to 189,000 AF on June 30, 2023. Precipitation within the groundwater basin was one hundred fifty eight percent of the long-term average during this water year, totaling 21.12 inches. Based on the groundwater basin conditions for the water year ending on June 30, 2023, OCWD may purchase up to 123,000 AF of water for groundwater replenishment during the ensuing water year, beginning on July 1, 2024, pursuant to the District Act.

A 350,000-year history of groundwater recharge in the southern Great Basin, USA

Nature Portfolio (Springer Nature) | March 31st, 2023

Estimating groundwater recharge under various climate conditions is important for predicting future freshwater availability. This is especially true for the water-limited

Estimating groundwater recharge under various climate conditions is important for predicting future freshwater availability. This is especially true for the water-limited region of the southern Great Basin, USA. To investigate the response of groundwater recharge to different climate states, we calculate the paleo recharge to a groundwater basin in southern Nevada over the last 350,000 years. Our approach combines a groundwater model with paleo-water-table data from Devils Hole cave. The minimum water-table during peak interglacial conditions was more than 1.6 m below modern levels, representing a recharge decline of less than 17% from present-day conditions. During peak glacial conditions, the water-table elevation was at least 9.5 m above modern levels, representing a recharge increase of more than 233–244% compared to present-day conditions. The elevation of the Devils Hole water-table is 3–4 times more sensitive to groundwater recharge during dry interglacial periods, compared to wet glacial periods. This study can serve as a benchmark for understanding long-term effects of past and future climate change on groundwater resources.

A Basin-Scale Approach to Estimating Recharge in the Desert: Anza-Cahuilla Groundwater Basin, CA

American Water Resources Association (AWRA) | November 2nd, 2021

The Anza-Cahuilla groundwater basin located mainly in the semi-arid headwaters of the Santa Margarita River watershed in southern California is the principle source of g

The Anza-Cahuilla groundwater basin located mainly in the semi-arid headwaters of the Santa Margarita River watershed in southern California is the principle source of groundwater for a rural disadvantaged community and two Native American Tribes, the Ramona Band of Cahuilla and the Cahuilla. Groundwater in the study area is derived entirely from precipitation and managing groundwater sustainably requires an accurate assessment of the water balance components, yet long-term estimates do not exist. Demand for groundwater in the region has increased and groundwater quality has decreased due to population growth and increased irrigated cropland. To characterize monthly long-term natural recharge and runoff estimates, a physically-based water balance model (Basin Characterization Model) was locally calibrated and validated using nearby streamgages and published estimates of climatic and hydrologic variables. The average modeled annual recharge and runoff from 1981 to 2010 was 5.4 × 106 and 1.2 × 107 m3, respectively, for the study area. Recharge and runoff do not reliably occur in large amounts every year and recharge rarely occurs in the groundwater basin footprint. These long-term estimates can be used by water managers, stakeholders, and Native American Tribes to develop plans for sustainable management of future water resources, and as inputs to a three-dimensional groundwater model.

A Bayesian approach to infer nitrogen loading rates from crop and land-use types surrounding private wells in the Central Valley, California

European Geosciences Union (EGU) | May 7th, 2018

This study is focused on nitrogen loading from a wide variety of crop and land-use types in the Central Valley, California, USA, an intensively farmed region with high�

This study is focused on nitrogen loading from a wide variety of crop and land-use types in the Central Valley, California, USA, an intensively farmed region with high agricultural crop diversity. Nitrogen loading rates for several crop types have been measured based on field-scale experiments, and recent research has calculated nitrogen loading rates for crops throughout the Central Valley based on a mass balance approach. However, research is lacking to infer nitrogen loading rates for the broad diversity of crop and land use types directly from groundwater nitrate measurements. Relating groundwater nitrate measurements to specific crops must account for the uncertainty about and multiplicity in contributing crops (and other land uses) to individual well measurements, and for the variability of nitrogen loading within farms and from farm to farm for the same crop type. In this study, we developed a Bayesian regression model that allowed us to estimate land-use-specific groundwater nitrogen loading rate probability distributions for 15 crop and land-use groups based on a database of recent nitrate measurements from 2149 private wells in the Central Valley. The water and natural, rice, and alfalfa and pasture groups had the lowest median estimated nitrogen loading rates, each with a median estimate below 5 kg N ha -1 yr -1. Confined animal feeding operations (dairies) and citrus and subtropical crops had the greatest median estimated nitrogen loading rates at approximately 269 and 65 kg N ha -1 yr-1, respectively. In general, our probability-based estimates compare favorably with previous direct measurements and with mass-balance-based estimates of nitrogen loading. Nitrogen mass-balance-based estimates are larger than our groundwater nitrate derived estimates for manured and non-manured forage, nuts, cotton, tree fruit, and rice crops. These discrepancies are thought to be due to groundwater age mixing, dilution from infiltrating river water, or denitrification between the time when nitrogen leaves the root zone (point of reference for mass-balance derived loading) and the time and location of groundwater measurement.

A brief geologic and hydrologic reconnaissance of the Furnace Creek Wash area, Death Valley National Monument, California

U.S. Geological Survey (USGS) | July 1st, 1964

A case study of canal seepage quantification using gain/loss method and electrical resistivity tomography in an intensively managed water resource system in the Treasure Valley, Idaho, United States

Elsevier | November 12th, 2024

Monitoring groundwater-surface water (GW-SW) interactions is essential for effectively managing the available water resources in semi-arid and arid environments. The focu

Monitoring groundwater-surface water (GW-SW) interactions is essential for effectively managing the available water resources in semi-arid and arid environments. The focus of this study was to quantify how much SW is being exchanged with the shallow GW aquifer in the Treasure Valley (TV), Idaho, USA. Previous water budgets estimated regional canal seepage without incorporating canal variability and flow measurement uncertainty. To address this, we applied both direct (gain/loss) and indirect (electrical resistivity tomography (ERT)) techniques. Direct seepage measurements were taken on canals capturing a range of different characteristics in the TV. The discrete measurements were then used to estimate the total seepage anticipated to be lost from these canals during the irrigation season. Our findings showed high seepage variability across the canals. The ERT inversion approach was utilized before and after the irrigation season by applying an advanced inversion scheme to better constrain the canal seepage spatial variability and uncertainty by quantifying changes in the saturated zone with 2D-ERT results. Temporal changes in the subsurface resistivity were observed due to the lateral flow from the nearby surface canal during the irrigation season. The combination of these approaches improves our understanding of SW-GW interactions in intensively managed irrigation systems.