One‐dimensional simulation of aquifer system compaction near Pixley, California: 1. Constant parameters

American Geophysical Union (AGU) | June 12th, 1975

Aggregate one‐dimensional compaction (consolidation) of a series of aquitards in a compacting aquifer system has been simulated through use of a finite difference repre

Aggregate one‐dimensional compaction (consolidation) of a series of aquitards in a compacting aquifer system has been simulated through use of a finite difference representation of the vertical stress distribution within an idealized aquitard. Among the parameters affecting the simulated compaction are two storage coefficients (compressibility values), one for recoverable and the other for nonrecoverable compression. These two storage coefficients introduce a transient heterogeneity within an aquitard that is generally ignored by hydrologists. A computer program with two sets of constant coefficients calculates the daily deformation due to observed changes in applied stress near Pixley, California. Although water levels fluctuate annually, no long‐term water level decline occurred near Pixley between January 1, 1959, and February 4, 1971. During this period, 3.19 ft (0.972 m) of compaction was observed. The net difference between simulated and observed compaction on February 4, 1971, was 1.3% of the observed value. Maximum deviation occurred in mid‐1964 and equaled 7% of the observed compaction.

Origin of methane and sources of high concentrations in Los Angeles groundwater

American Geophysical Union (AGU) | February 12th, 2018

High dissolved methane gas concentrations were measured in 37 groundwater samples collected in the Los Angeles Basin, California. The origin of the methane was identified

High dissolved methane gas concentrations were measured in 37 groundwater samples collected in the Los Angeles Basin, California. The origin of the methane was identified as microbial activity rather than from the burial and heating of organic material. The source of the methane was microbial production in shallow, oxygen-depleted aquifers rather than the upward migration or leakage of methane associated with oil fields in the basin.

Over‐pumping leads to California groundwater arsenic threat

Nature Portfolio (Springer Nature) | June 5th, 2018

Water resources are being challenged to meet domestic, agricultural, and industrial needs. To complement finite surface water supplies that are being stressed b

Water resources are being challenged to meet domestic, agricultural, and industrial needs. To complement finite surface water supplies that are being stressed by changes in precipitation and increased demand, groundwater is increasingly being used. Sustaining groundwater use requires considering both water quantity and quality. A unique challenge for groundwater use, as compared with surface water, is the presence of naturally occurring contaminants within aquifer sediments, which can enter the water supply. Here we find that recent groundwater pumping, observed through land subsidence, results in an increase in aquifer arsenic concentrations in the San Joaquin Valley of California. By comparison, historic groundwater pumping shows no link to current groundwater arsenic concentrations. Our results support the premise that arsenic can reside within pore water of clay strata within aquifers and is released due to overpumping. We provide a quantitative model for using subsidence as an indicator of arsenic concentrations correlated with groundwater pumping.

Overpumping leads to California groundwater arsenic threat

Nature Portfolio (Springer Nature) | June 5th, 2018

Water resources are being challenged to meet domestic, agricultural, and industrial needs. To complement finite surface water supplies that are being stressed b

Water resources are being challenged to meet domestic, agricultural, and industrial needs. To complement finite surface water supplies that are being stressed by changes in precipitation and increased demand, groundwater is increasingly being used. Sustaining groundwater use requires considering both water quantity and quality. A unique challenge for groundwater use, as compared with surface water, is the presence of naturally occurring contaminants within aquifer sediments, which can enter the water supply. Here we find that recent groundwater pumping, observed through land subsidence, results in an increase in aquifer arsenic concentrations in the San Joaquin Valley of California. By comparison, historic groundwater pumping shows no link to current groundwater arsenic concentrations. Our results support the premise that arsenic can reside within pore water of clay strata within aquifers and is released due to overpumping. We provide a quantitative model for using subsidence as an indicator of arsenic concentrations correlated with groundwater pumping.

Owens Valley Groundwater Basin Final Groundwater Sustainability Plan

Owens Valley Groundwater Authority | December 9th, 2021

The Owens Valley Groundwater Basin and Fish Slough subbasin (Basin) were assigned a low priority status by the California Department of Water Resources (DWR) and are not

The Owens Valley Groundwater Basin and Fish Slough subbasin (Basin) were assigned a low priority status by the California Department of Water Resources (DWR) and are not required to be managed by a Groundwater Sustainability Agency (GSA). GSAs in low priority basins are encouraged to complete a GSP. Following the adoption of the Sustainable Groundwater Management Act (SGMA), the Basin was originally ranked as medium priority, but DWR proposed it be assigned high priority and ultimately ranked the Basin as low priority in December 2019. Despite the uncertainty in the Basin ranking before the final ranking was announced the Owens Valley Groundwater Authority (OVGA) elected to prepare a GSP for the Basin. This document is the GSP, and it was developed in accordance with Sustainable Groundwater Management Act (SGMA) statutory and regulatory requirements. This GSP describes the Basin, develops quantifiable management objectives that account for the interests of beneficial groundwater uses and users, and identifies a group of management actions that will maintain sustainable conditions in the Basin for 20 years after plan adoption. This GSP also contains steps a GSA could undertake to manage pumping to address declining water levels in a portion of the Basin. Preparation and implementation of the GSP by the OVGA is discretionary as long as the Basin remains very low or low priority. This GSP does not pertain to lands in the Basin that are exempt from SGMA, e.g. Federal and state owned lands, Tribal Reservations, and Los Angeles Department of Water and Power (LADWP) lands managed pursuant to the Long Term Water Agreement (LTWA). LADWP lands in Inyo County are referred to as adjudicated; other lands in the Basin are referred to as GSP lands in this document. Los Angeles-owned lands in the Basin in Mono County are not exempt from SGMA. Due to size, the file has been divided into five parts. Part 1, Part 2, Part 3, Part 4, Part 5

Pajaro Valley Basin Management Plan Groundwater Sustainability Update 2022

Pajaro Valley Water Management Agency (PVWMA) | November 17th, 2021

Pajaro Valley Water Management Agency Basin Management Plan Update

Pajaro Valley Water Management Agency (PVWMA) | February 14th, 2014

Pajaro Valley Water Management Agency Revised Management Plan

Pajaro Valley Water Management Agency (PVWMA) | February 14th, 2002

Paso Robles Subbasin Groundwater Sustainability Plan

Paso Robles Subbasin Cooperative Committee | November 13th, 2019

Paso Robles Subbasin Groundwater Sustainability Plan (Revised)

Paso Robles Subbasin Groundwater Sustainability Agencies | June 13th, 2022

This Groundwater Sustainability Plan (GSP) fulfills the requirements of the Sustainable Groundwater Management Act (SGMA) for the Paso Robles Subbasin of the Salinas Vall

This Groundwater Sustainability Plan (GSP) fulfills the requirements of the Sustainable Groundwater Management Act (SGMA) for the Paso Robles Subbasin of the Salinas Valley Basin. The sustainability goal of this GSP is to sustainably manage the groundwater resources of the Paso Robles Subbasin for long-term community, financial, and environmental benefit of Subbasin users. This GSP outlines the approach to achieve a sustainable groundwater resource free of undesirable results within 20 years, while maintaining the unique cultural, community, and business aspects of the Subbasin. In adopting this GSP, it is the express goal of the GSAs to balance the needs of all groundwater users in the Subbasin, within the sustainable limits of the Subbasin’s resources. The GSP describes the Paso Robles Subbasin, develops quantifiable management objectives that consider the interests of the Subbasin’s beneficial groundwater uses and users, and identifies management actions and conceptual projects that will allow the Subbasin to achieve sustainability by 2040. This GSP covers the entire Paso Robles Subbasin. The Paso Robles Subbasin GSP has been jointly developed by four Groundwater Sustainability Agencies (GSAs): • City of Paso Robles GSA • Paso Basin - County of San Luis Obispo GSA • San Miguel Community Services District (CSD) GSA • Shandon - San Juan GSA Submitted to the California Department of Water Resources (DWR) in January 2021, the first version of this GSP was reviewed by DWR in January 2022 and determined to be incomplete (DWR, 2022). Corrective actions were provided by DWR for two identified deficiencies; these corrective actions are incorporated into this June 13, 2022 GSP for resubmittal to DWR. Due to size, this file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6