Source, movement and age of groundwater in the upper part of the Mojave River Basin, California, USA

Proceedings of the 1994 International Symposium on Application of Tracers in Arid Zone Hydrology | August 22nd, 1996

Water samples from wells were collected and analysed for oxygen-18, deuterium, tritium, carbon-14, and carbon-13 to determine the source, movement and age of groundwate

Water samples from wells were collected and analysed for oxygen-18, deuterium, tritium, carbon-14, and carbon-13 to determine the source, movement and age of groundwater in the upper part of the Mojave River basin. Water in the alluvial aquifer has a median deuterium composition of — 66% and contains tritium, and was recently recharged by water from the Mojave River. Water in the regional aquifer near the Mojave River, near Summit Valley, and underlying several small washes has deuterium compositions heavier than — 60 %. Although some water in the regional aquifer near the Mojave River contains tritium, most of this water does not contain tritium. Carbon-14 data indicate that this water was recharged less than 2400 years ago. Water in the remainder of the regional aquifer has a median deuterium composition of — 84 %, which is as much as 20 % lighter than the volume-weighted deuterium composition of present-day precipitation. These data show that this water was recharged under climatic conditions different from average conditions today. Carbon-14 data indicate that some water in the regional aquifer was recharged more than 20,000 years ago.

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 Coast Hydrologic Region Groundwater Update

California Department of Water Resources (DWR) | April 1st, 2015

The primary goal of the South Coast Hydrologic Region (South Coast region) groundwater update is to expand information about region-specific groundwater conditions for Ca

The primary goal of the South Coast Hydrologic Region (South Coast region) groundwater update is to expand information about region-specific groundwater conditions for California Water Plan Update 2013 and to guide more informed groundwater management actions and policies. A second goal is to steadily improve the quality of groundwater information in future California Water Plan (CWP) updates to a level that will enable regional water management groups (RWMGs) to accurately evaluate their groundwater resources and implement management strategies that can meet local and regional water resource objectives within the context of broader statewide objectives. The final goal is to identify data gaps and groundwater management challenges that will guide prioritizing of future data collection and funding opportunities relevant to the region. This regional groundwater update is not intended to provide a comprehensive and detailed examination of local groundwater conditions, or be a substitute for local studies and analysis. Nonetheless, where information is readily available, this update does report some aspects of the regional groundwater conditions in greater detail.

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

South Lahontan Hydrologic Region Groundwater Update

California Department of Water Resources (DWR) | April 1st, 2015

The primary goal of the South Lahontan Hydrologic Region (South Lahontan region) groundwater update is to expand information about region-specific groundwater conditions

The primary goal of the South Lahontan Hydrologic Region (South Lahontan region) groundwater update is to expand information about region-specific groundwater conditions for California Water Plan Update 2013, and to guide more informed groundwater management actions and policies. A second goal is to steadily improve the quality of groundwater information in future California Water Plan (CWP) updates to a level that will enable regional water management groups (RWMGs) to accurately evaluate their groundwater resources and implement management strategies that can meet local and regional water resource objectives within the context of broader statewide objectives. The final goal is to identify data gaps and groundwater management challenges that will guide prioritizing of future data collection and funding opportunities relevant to the region. This regional groundwater update is not intended to provide a comprehensive and detailed examination of local groundwater conditions, or be a substitute for local studies and analysis. Nonetheless, where information is readily available, this update does report some aspects of the regional groundwater conditions in greater detail.

South of Kern River Groundwater Sustainability Plan (GSP) for Certain Lands Overlying the Kern County Subbasin

South of the Kern River Groundwater Sustainability Agencies (SoKR GSAs) | July 27th, 2022

Special Issue: The Sustainable Groundwater Management Act

California Agriculture (UCANR) | March 13th, 2018

This special issue of California Agriculture focuses on the implications of the Sustainable Groundwater Management Act, or SGMA, the package of bills signed into law by C

This special issue of California Agriculture focuses on the implications of the Sustainable Groundwater Management Act, or SGMA, the package of bills signed into law by California Gov. Jerry Brown in September 2014. The legislation puts California on a path to the sustainable management of a resource that accounts for between one-third (in wet years) and two-thirds (in dry years) of the state’s water use. In dry years, statewide overdraft is in the range of 3 to 7 million acre-feet. Some of that is recharged in wet years, but in many basins, including some of the state’s top-producing agricultural regions, the long-term trend has been falling water tables (see groundwater.ucdavis.edu for links to UC video introductions to groundwater in California and SGMA). Sustainable management under the act is defined as the avoidance of “significant and unreasonable” levels of six impacts: (1) lowering of groundwater levels, (2) reduction in groundwater storage, (3) seawater intrusion, (4) water quality degradation, (5) land subsidence and (6) impacts on beneficial uses of interconnected surface waters. Regulation of groundwater in California was long in coming. The state has often been a national leader in environmental policy, for instance on air quality and greenhouse gas emissions. But it was the last state to adopt statewide groundwater regulations (Cannon Leahy 2016). In most basins, groundwater use was unrestricted beyond the basic requirement in the state constitution that all water use be reasonable and beneficial. Of the state’s 515 groundwater basins, SGMA applies to the 127 judged to be high- or medium-priority based on a combination of factors related to current and future groundwater demand and the consequences of overdraft. These 127 basins account for 96% of the state’s groundwater extraction (CASGEM 2018). Twenty-seven of these basins have previously been adjudicated — meaning that they are under a court order to limit overdraft. The act mandated the creation, by June 30, 2017, of a new set of local agencies, groundwater sustainability agencies (GSAs), responsible for complying with SGMA’s directives. To date, 266 groundwater sustainability agencies have been formed, accounting for 378 areas in 141 basins statewide (in many cases there is more than one GSA in a basin; also, GSAs may be formed in low-priority basins even though the law does not require it). The next step is the preparation of groundwater sustainability plans. These plans must put the basin on a path that will lead to sustainable management within 20 years, with interim milestones subject to state review every 5 years. Critically overdrafted basins (map) must submit plans by January 31, 2020; other basins must submit by January 31, 2022. Two state agencies have primary responsibility for supporting the implementation of SGMA. The Department of Water Resources acts as facilitator and evaluator, while the State Water Resources Control Board has an enforcement role, ensuring compliance with the law (see article page 18).