Groundwater Sustainability Plan for the Delta-Mendota Subbasin

Delta-Mendota Subbasin Coordination Committee | July 31st, 2024

1. Table of Contents 2. Executive Summary 3. Introduction 4. Plan Area 5. Basin Setting 6. Groundwater Conditions 7. Water Budget 8. Sustainability Criteria 9

1. Table of Contents 2. Executive Summary 3. Introduction 4. Plan Area 5. Basin Setting 6. Groundwater Conditions 7. Water Budget 8. Sustainability Criteria 9. Monitoring 10. Projects and Management 11. Plan Implementation 12. References 13. Appendices For a full history of basin GSPs, go to the Department of Water Resources Sustainable Groundwater Management Act portal.

Groundwater Sustainability Plan for the Las Posas Valley Basin

Fox Canyon Groundwater Management Agency (FCGMA) | December 13th, 2019

The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency), has developed this Groundwater Sustainability Plan (GSP) for the Las Posas Valley Basin (LPVB; DWR B

The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency), has developed this Groundwater Sustainability Plan (GSP) for the Las Posas Valley Basin (LPVB; DWR Basin 4-008) in compliance with the 2014 Sustainable Groundwater Management Act (SGMA) (California Water Code, Section 10720 et seq.). FCGMA is one of three Groundwater Sustainability Agencies (GSAs) in the LPVB. The other two GSAs are the Camrosa Water District GSA–Las Posas Valley and the Las Posas Valley Outlying Areas GSA. This GSP is the sole GSP prepared for the LPVB, and covers the entire LPVB, including all areas of the LPVB outside of FCGMA’s jurisdiction. The purpose of this GSP is to define the conditions under which the groundwater resources of the entire LPVB, which support agricultural, municipal and industrial, and environmental uses, will be managed sustainably in the future. Although the California Department of Water Resources (DWR) has defined the LPVB as a single groundwater basin, the western and eastern parts of the basin are hydraulically separated from each other by the Somis Fault, a geologic feature that inhibits groundwater flow across it. As a result, groundwater conditions on the west side of the fault in the Fox Canyon Aquifer and Grimes Canyon Aquifer, two primary aquifers in the LPVB, differ from conditions on the east side of the fault. Furthermore, the Epworth Gravels Aquifer, located on the east side of the fault is hydrologically separated from the Fox Canyon Aquifer and Grimes Canyon Aquifer. Hydrologic differences in the controls on, and responses to, both recharge and groundwater production necessitate the definition of three separate management areas in the LPVB. These three management areas are the West Las Posas Management Area (WLPMA), the East Las Posas Management Area (ELPMA), and the Epworth Gravels Management Area. The hydrologic conditions, sustainable yield, and sustainability criteria are discussed and defined by management area throughout this GSP. Historical groundwater production in the LPVB has resulted in chronic declines in groundwater levels and loss of groundwater in storage in parts of each of the three management areas. In the WLPMA, the average rate of groundwater production between 2015 and 2017 was approximately 14,000 acre-feet per year (AFY). In the ELPMA and the Epworth Gravels Management Area, the average rate of groundwater production between 2015 and 2017 was approximately 20,500 AFY and 1,500 AFY, respectively. Numerical groundwater simulations indicate that if these production rates were carried into the future, groundwater elevations in each of the management areas of the LPVB would not recover during multi-year cycles of drought and recovery. In order to determine the sustainable yield of each management area, combinations of projects and management actions were explored to estimate the rate of groundwater production that would prevent chronic declines in groundwater elevation and ongoing loss of groundwater storage in the future. Additionally, in the WLPMA, the numerical groundwater model simulations were used to assess the influence of groundwater conditions on the adjacent Oxnard Subbasin. In the ELPMA, numerical groundwater simulations were also used to assess zones of the Fox Canyon Aquifer that are most prone to conversion from confined to unconfined conditions. The rate of groundwater production that avoids chronic water level declines, loss of storage, potential land subsidence, and impacts to adjacent basins is referred to as the sustainable yield for each management area. With the currently available projects and management actions, the sustainable yield of the WLPMA is approximately 12,500 AFY, with an uncertainty estimate of ±1,200 AFY (Table ES-1). In the ELPMA, the total sustainable yield (including the Epworth Gravels Management Area) is estimated to be 17,800 AFY ±2,300 AFY. For the Epworth Gravels Management Area only, the sustainable yield is estimated to be approximately 1,300 AFY. Except for the Epworth Gravels Management Area, both the historical (1985–2015) and recent (2015–2017) groundwater production rates exceeded the upper end of the future sustainable yield estimates (Table ES-1). Adoption of this GSP represents the first step in achieving groundwater sustainability within the. LPVB, as required by SGMA. SGMA requires that groundwater in each of the management areas of the LPVB be managed sustainably within 20 years of adoption of the GSP. SGMA also requires that this GSP be evaluated at a minimum of every 5 years after adoption. As part of the 5-year evaluation process, the sustainable yield will be refined and adjusted. These refinements will be based on new data, additional studies undertaken to fill data gaps, and groundwater modeling. Refinements and adjustments will also be made to the minimum threshold groundwater levels developed to avoid undesirable results, the measurable objective groundwater levels that account for the need to continue groundwater production during drought cycles and the associated interim milestones to help gauge progress toward sustainability over the next 20 years. The required 5-year evaluations will also examine both new water supply projects, and the potential impacts of extractions rates on groundwater elevations and sustainability in the LPVB. Additional modeling is recommended during the 5-year update process to understand how changes in pumping and additional new water supply projects can increase the overall sustainable yield of the different management areas of the LPVB. As this understanding improves, projects to support increases in the overall sustainable yield can be developed.

Groundwater Sustainability Plan for the Northern and Central Delta-Mendota Regions

San Luis & Delta-Mendota Water Authority (SLDMWA) | November 30th, 2019

Table of Contents Executive Summary Introduction Plan Area Governance and Administration Outreach and Communication Basin Setting Sustainable M

Table of Contents Executive Summary Introduction Plan Area Governance and Administration Outreach and Communication Basin Setting Sustainable Management Criteria Sustainability Implementation Plan Implementation Technical Studies Appendices A. Coordination Agreements B. Common Chapter C. Outreach Documentation D. Water Budget Model Documentation E. Hydrographs for Sustainable Management Criteria F. Quality Assurance Program G. Noticing and Adoption Implementation H. Elements Guide

Groundwater Sustainability Plan for the Oxnard Subbasin

Fox Canyon Groundwater Management Agency (FCGMA) | December 13th, 2019

The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency) has developed this Groundwater Sustainability Plan (GSP) for the Oxnard Subbasin (Subbasin; DWR Basin

The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency) has developed this Groundwater Sustainability Plan (GSP) for the Oxnard Subbasin (Subbasin; DWR Basin 4-004.02) of the Santa Clara River Valley Groundwater Basin (DWR Basin 4-004), in compliance with the 2014 Sustainable Groundwater Management Act (SGMA; California Water Code, Section 10720 et seq.). The purpose of this GSP is to define the conditions under which the groundwater resources of the entire Oxnard Subbasin, which support agricultural, municipal and industrial, and environmental uses, will be managed sustainably in the future. Historical groundwater production has resulted in seawater intrusion in the five primary aquifers of the Subbasin. These aquifers have been divided into an Upper Aquifer System, which comprises the Oxnard and Mugu Aquifers, and a Lower Aquifer System, which comprises the Hueneme, Fox Canyon, and Grimes Canyon Aquifers. The average rate of groundwater production from the Upper Aquifer System between 2015 and 2017 was approximately 40,000 acre-feet per year (AFY). The average production from the Lower Aquifer System between 2015 and 2017 was approximately 29,000 AFY. Numerical groundwater simulations indicate that if these production rates were carried into the future, seawater intrusion would continue in the Subbasin and the area currently impacted by concentrations of chloride greater than 500 milligrams per liter would grow. The landward extent of this area is referred to as the saline water impact front. Combinations of projects and management actions were explored to estimate the rate of groundwater production that would prevent future expansion of the area of the Subbasin currently impacted by concentrations of chloride greater than 500 milligrams per liter. This rate of groundwater production is referred to as the sustainable yield. With the currently available projects and management actions, the sustainable yield of the Upper Aquifer System, was calculated to be approximately 32,000 AFY, with an uncertainty of ± 4,100 to 6,000 AFY. The sustainable yield of the Lower Aquifer System was calculated to be approximately 7,000 AFY, with an uncertainty of ± 2,300 to 3,600 AFY. Adoption of this GSP represents the first step in achieving groundwater sustainability within the Oxnard Subbasin by 2040, as required by SGMA. Evaluation of this GSP is required at a minimum of every 5 years following submittal to the California Department of Water Resources (DWR). As part of the 5-year evaluation process, the sustainable yield for each aquifer system will be refined and adjusted. These refinements will be based on new data, additional studies undertaken to fill data gaps, and groundwater modeling. Refinements and adjustments will also be made to the minimum threshold water levels developed to avoid undesirable results, the measurable objective water levels that account for the need to continue groundwater production during drought cycles and the associated interim milestones to help gauge progress toward sustainability over the next 20 years. In order to minimize the pumping reductions required to achieve sustainable management of the Subbasin, investment in large-scale projects to increase water supply, provide the infrastructure to redistribute pumping, and/or directly control seawater intrusion should be investigated. Basin optimization studies, groundwater modeling, and project feasibility studies will be conducted over the next 5 years to explore practicable processes and approaches to increasing the sustainable yield of the Oxnard Subbasin.

Groundwater Sustainability Plan for the Pleasant Valley Basin

Fox Canyon Groundwater Management Agency (FCGMA) | December 13th, 2019

The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency) has developed this Groundwater Sustainability Plan (GSP) for the Pleasant Valley Basin (PVB; DWR Basi

The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency) has developed this Groundwater Sustainability Plan (GSP) for the Pleasant Valley Basin (PVB; DWR Basin 4-006), in compliance with the 2014 Sustainable Groundwater Management Act (SGMA) (California Water Code, Section 10720 et seq.). FCGMA is one of three Groundwater Sustainability Agencies (GSAs) in the PVB. The other two GSAs are the Camrosa Water District–Pleasant Valley GSA and the Pleasant Valley Outlying Areas GSA. This GSP is the sole GSP prepared for the PVB, and covers the entire PVB, including all areas of the PVB outside of FCGMA’s jurisdiction. The purpose of this GSP is to define the conditions under which the groundwater resources of the entire PVB, which support agricultural, municipal and industrial, and environmental uses, will be managed sustainably in the future. The PVB shares a boundary and is in hydraulic communication with Oxnard Subbasin (Subbasin; DWR Basin 4-004.02) to the west. The boundary between the PVB and the Oxnard Subbasin is associated with a change in character of recent and older alluvial deposits. In the PVB, these deposits are finer grained and are, in general, less suitable for groundwater production than the coarser-grained sediments of the same age in the Oxnard Subbasin. There is no corresponding change in character in the deeper aquifers, including the Fox Canyon Aquifer, which are continuous across the boundary between the PVB and the Oxnard Subbasin. Groundwater production from wells on either side of the boundary between the PVB and the Oxnard Subbasin influences groundwater elevations and the direction of groundwater flow across this boundary. Historical groundwater production from the PVB and Oxnard Subbasin combined has resulted in seawater intrusion in the aquifers of the Subbasin. In the PVB, the average rate of groundwater production between 2015 and 2017 was approximately 13,200 acre-feet per year (AFY). In 2015, approximately 53% of the production from the Lower Aquifer System, which comprises the Hueneme, Fox Canyon, and Grimes Canyon Aquifers, and 47% of the production from the Upper Aquifer System, which comprises the older alluvium in the PVB, and the Oxnard and Mugu Aquifers in the Oxnard Subbasin. Numerical groundwater simulations indicate that if these production rates were carried into the future, groundwater elevations in the PVB would not recover during multi-year cycles of drought and recovery, and seawater intrusion would continue in the Oxnard Subbasin. The landward extent of the area in the Subbasin currently impacted by concentrations of chloride greater than 500 milligrams per liter is referred to as the “saline water impact front.” Combinations of projects and management actions were explored to estimate the rate of groundwater production that would allow groundwater elevations in the PVB to recover during multi-year cycles of drought and recovery, and prevent future landward migration of the saline water impact front. This rate of groundwater production is referred to as the sustainable yield. With the currently available projects and management actions, the sustainable yield of the PVB was estimated to be approximately 11,600 AFY, with an uncertainty of ± 1,200 AFY. At the upper bound of the uncertainty estimate (12,600 AFY), the estimated sustainable yield of the PVB is 600 AFY lower than the 2015–2017 average production rate. Adoption of this GSP represents the first step in achieving groundwater sustainability within the PVB by 2040, as required by SGMA. Evaluation of this GSP is required at a minimum of every 5 years following submittal to the California Department of Water Resources (DWR). As part of the 5-year evaluation process, the sustainable yield will be refined and adjusted. These refinements will be based on new data, additional studies undertaken to fill data gaps, and groundwater modeling. Refinements and adjustments will also be made to the minimum threshold groundwater levels developed to avoid undesirable results, the measurable objective groundwater levels that account for the need to continue groundwater production during drought cycles and the associated interim milestones to help gauge progress toward sustainability over the next 20 years. In order to minimize the pumping reductions required to achieve sustainable management of the PVB, investment in projects to increase water supply, provide the infrastructure to redistribute pumping, and/or directly control seawater intrusion in the Oxnard Subbasin should be investigated. Inter-basin optimization studies, groundwater modeling, and project feasibility studies are recommended over the next 5 years to explore practicable processes and approaches to increasing the sustainable yield of the PVB. Due to size, this file has been divided. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6

Groundwater Sustainability Plan for the San Joaquin River Exchange Contractors Groundwater Sustainability Plan (GSP) Group in the Delta-Mendota Subbasin

San Joaquin River Exchange Contractors GSA (SJREC GSA) | December 13th, 2019

Groundwater Sustainability Plan Greater Kaweah Groundwater Sustainability Agency

Greater Kaweah Groundwater Sustainability Agency (GKGSA) | January 22nd, 2020

Groundwater Sustainability Plan, County of Fresno Groundwater Sustainability Agency, Management Area A and Management Area B, Delta-Mendota Subbasin

County of Fresno | January 23rd, 2020

Groundwater Sustainability Plan, Olcese Groundwater Sustainability Agency, Kern County Subbasin

Olcese Groundwater Sustainability Agency | January 30th, 2020

Groundwater Transport: Handbook of Mathematical Models

American Geophysical Union (AGU) | January 1st, 1984

Published by the American Geophysical Union as part of the Water Resources Monograph Series, Volume 10. Concerns over groundwater pollution have resulted in the passag

Published by the American Geophysical Union as part of the Water Resources Monograph Series, Volume 10. Concerns over groundwater pollution have resulted in the passage of legislation during the last decade calling for pollution control and remedial measures to ensure proper drinking water quality. There are two main types of groundwater pollution caused by man: (1) pollution caused by the use of pesticides, herbicides, and fertilizers over agricultural lands, where the source of contamination covers a relatively large area, and (2) pollution caused by industries and municipalities, which is generally more localized. For the second type, because the contamination in the groundwater is localized, the design of any remedial measure requires knowledge of the extent of the contaminant plume. Various mathematical methods may be used for estimating the size, shape, and development of a localized contaminant plume. It is the need for these mathematical methodologies that forms the main impetus for the preparation of this monograph.