Source, Movement, and Age of Ground Water in a Coastal California Aquifer

U.S. Geological Survey (USGS) | July 11th, 1996

Understanding the contribution of recharge from different sources is important to the management of ground-water supply in coastal aquifers in California especial

Understanding the contribution of recharge from different sources is important to the management of ground-water supply in coastal aquifers in California especially where water-supply or water-quality problems have developed as a result of ground-water pumping. In areas where water levels have changed greatly as a result of pumping and no longer reflect predevelopment conditions, an analysis of isotopic data can provide information about the source, movement, and age of ground water that is not readily obtained from a more traditional analysis of ground-water data This information can be used to develop management strategies that incorporate the availability of natural and artificial recharge to control water-level declines and water-quality degradation. In this study, the ratios of the stable isotopes of oxygen and hydrogen were used to determine the source and trace the movement of ground water in the Santa Clara-Calleguas basin, Ventura County, California Tritium and carbon-14 data were used to estimate the age (time since recharge) of ground water.

Sources of high-chloride water and managed aquifer recharge in an alluvial aquifer in California, USA

Hydrogeology Journal (Springer) | July 3rd, 2015

South American Subbasin Groundwater Sustainability Plan

Sacramento County | October 29th, 2021

Groundwater management in the South American Subbasin (SASb) has been occurring for decades. Stable groundwater conditions in terms of groundwater levels, storage volume

Groundwater management in the South American Subbasin (SASb) has been occurring for decades. Stable groundwater conditions in terms of groundwater levels, storage volume, and interconnected surface waters have been achieved due to a variety of historically implemented projects and management actions. To ensure continued sustainable conditions allowing for future groundwater use to the benefit of all users in the SASb over the next 50-years, with climate change considered, a groundwater sustainability plan (GSP) has been developed and will be implemented to achieve the sustainability goal for the basin in the next 20 years. Due to size, this file has been divided into eight parts. Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8

South Kings Groundwater Sustainability Agency Groundwater Sustainability Plan

South Kings Groundwater Sustainability Agency | December 19th, 2019

South Kings Groundwater Sustainability Agency Groundwater Sustainability Plan (Revised)

South Kings Groundwater Sustainability Agency | July 13th, 2022

State of the Salinas River Groundwater Basin

Monterey County Water Resources Agency (MCWRA) | January 16th, 2015

From 6.3 Steps Appropriate to Address Water Supply under Continued Drought Conditions:  Based on the continued large storage declines in the East Side and Pressure Su

From 6.3 Steps Appropriate to Address Water Supply under Continued Drought Conditions:  Based on the continued large storage declines in the East Side and Pressure Subareas (and resulting groundwater head declines and seawater intrusion), the current distribution of groundwater extractions is not sustainable. Seawater intrusion can account for up to 18,000 afy of the total storage loss of up to 24,000 afy. Sustainable use of groundwater can only be achieved by aggressive and cooperative water resources management. The consequences of no-action under continued drought conditions will be the imminent advancement of seawater intrusion within the next few years and the continued decline of groundwater head. Both of these conditions would necessitate the drilling of deeper groundwater wells, which may not be feasible in some areas because of lower groundwater yield and water quality in the Pressure Deep Aquifer. A more sustainable long-term management practice would encourage the Basin-wide redistribution and reduction of groundwater pumping, which would require cooperative and aggressive resource management. The unsustainability of the current distribution of groundwater extractions has long been recognized by various investigators, and a Basin-wide redistribution and reduction in pumping has been recommended previously (e.g. DWR, 1946). 6.3.1 Technical Option 1:  The large storage declines that have occurred in the Basin in the past, especially in the East Side Subarea, have created a significant landward groundwater head gradient that must be reversed before seawater intrusion can be halted. Reduction of pumping in the Pressure and East Side Subareas could help mitigate some of the anticipated effects of extended drought on groundwater storage and water quality in the study area. Shifting of pumping to areas further away from the coast would also be helpful, as long as it is shifted south of the current head trough (Figure ES3) that exists in the East Side Subarea. One of the main reasons that substantial steps must be taken to curtail seawater intrusion is that the large storage declines that have occurred in the Basin in the past (especially in the East Side Subarea) have created a significant landward groundwater head gradient that must be reversed before seawater intrusion can be halted. 6.3.2 Technical Option 2: The shifting of some pumping from the P-180 and P-400 Aquifers to the Pressure Deep Aquifer would reduce the storage deficit in the shallower aquifers; however, this would necessarily lead to head declines in the Pressure Deep Aquifer. Unlike the P-180 and P-400 Aquifers, it is not known whether or not the Pressure Deep Aquifer is hydraulically connected to the ocean in Monterey Bay, so it is not known whether this pumping shift would lead to the onset of regional seawater intrusion. Also unknown is the likelihood of localized interaquifer seawater mixing between the Pressure 400- Foot Aquifer and the Pressure Deep Aquifer. Hence, this Management Option requires more investigation to determine its feasibility. 6.3.3 Evaluation of Potential Solutions: The numerical modeling analysis to be performed as a second part of this Basin Investigation will consider the effects of various management decisions on the water supply and water quality in the study area. The primary questions to be assessed for each scenario are: 1) what will be the rate of groundwater head decline; and, 2) what will be the rate of increase in acreage with impaired water quality due to the advancement of the seawater intrusion front. We can then assess the economic effects of 1) and 2) due to water supply wells becoming inoperable (i.e. dry), and the further loss of aquifer storage capacity due to the advancement of seawater intrusion. The numerical model should be used to predict groundwater head declines under different management scenarios, including implementing targeted pumping rates and optimizing the distribution of pumping. Future declines in groundwater head must be evaluated by simulated groundwater conditions so that “trigger (groundwater) head levels” can be used as a measure of safe yield and an early alert system as part of Basin Management Objectives. That analysis will extend the discussions and conclusions presented in this report.

Statement of Findings Regarding the Periodic Review and Approval of the Santa Clara Valley – Niles Cone Subbasin Alternative Groundwater Sustainability Plan

California Department of Water Resources (DWR) | June 27th, 2024

Statement of Findings regarding the Approval of the Sacramento Valley – Antelope Subbasin 2024 Groundwater Sustainability Plan

California Department of Water Resources (DWR) | February 27th, 2025

Statement of Findings regarding the Determination of Incomplete Status of the San Joaquin Valley - Merced Subbasin Groundwater Sustainability Plan

California Department of Water Resources (DWR) | January 28th, 2022

The Department of Water Resources (Department) is required to evaluate whether a submitted groundwater sustainability plan (GSP or Plan) conforms to specific requirements

The Department of Water Resources (Department) is required to evaluate whether a submitted groundwater sustainability plan (GSP or Plan) conforms to specific requirements of the Sustainable Groundwater Management Act (SGMA or Act), is likely to achieve the sustainability goal for the basin covered by the Plan, and whether the Plan adversely affects the ability of an adjacent basin to implement its GSP or impedes achievement of sustainability goals in an adjacent basin. (Water Code   10733.) The Department is directed to issue an assessment of the Plan within two years of its submission. (Water Code 10733.4.) This Statement of Findings explains the Department’s decision regarding the Plan submitted jointly by the Merced Irrigation-Urban Groundwater Sustainability Agency (GSA), Merced Subbasin GSA, and Turner Island Water District GSA #1 (collectively, the GSAs) for the San Joaquin Valley – Merced Subbasin (No. 5-022.04). Department management has reviewed the enclosed Staff Report, which recommends that the identified deficiencies should preclude approval of the GSP. Based on its review of the Staff Report, Department management is satisfied that staff have conducted a thorough evaluation and assessment of the Plan and concurs with, and hereby adopts, staff’s recommendation and all the corrective actions provided. The Department thus deems the Plan incomplete based on the Staff Report and the findings contained herein.

Statistical Clustering of Major Solutes: Use as a Tracer for Evaluating Interbasin Groundwater Flow into Indian Wells Valley, California

Geological Society of America (GSA) | February 9th, 2006

Many previous studies have demonstrated use of specific solutes or isotopes as tracers of groundwater flow. We present a technique that uses standard hydrochemical inform

Many previous studies have demonstrated use of specific solutes or isotopes as tracers of groundwater flow. We present a technique that uses standard hydrochemical information to create statistically based hydrochemical facies, which are then used as tracers of groundwater flow. This approach reduces potential subjective bias during interpretation of single tracer data in complex systems with multiple sources or conflicting multiple tracer data. Standard hydrochemical data from 1,368 water samples that spanned more than 80 years were analyzed using cluster analysis to decipher groundwater flow paths in Indian Wells Valley (IWV), California. The statistically derived hydrochemical facies form distinct spatial patterns in which all major-ion concentrations increase progressively from Sierra Nevada (recharge) to China Lake playa (discharge), consistent with the topographically driven flow of groundwater (the typical case for basin and range flow systems). However, once individual samples could be placed in the context of the normal hydrochemical evolution, anomalies are readily identifiable. The distribution of water chemistry in the southeastern part of the IWV does not conform to the regional trend. Groundwater from that part of the IWV is statistically more similar to waters from the Kern Plateau area (in the high Sierra Nevada outside the local watershed) than to waters from the local watershed. The groundwater is interpreted to originate from the fracture-directed interbasin flow from the Kern Plateau area that is directly recharging the alluvial aquifer in the subsurface. Inclusion of this flow could substantially alter current water budgets and water resources management approaches.