Stratigraphic controls on seawater intrusion and implications for groundwater management, Dominguez Gap area of Los Angeles, California, USA

Hydrogeology Journal (Springer) | May 30th, 2009

Groundwater pumping has led to extensive waterlevel declines and seawater intrusion in coastal Los Angeles, California (USA). A SUTRA-based solute-transport model was dev

Groundwater pumping has led to extensive waterlevel declines and seawater intrusion in coastal Los Angeles, California (USA). A SUTRA-based solute-transport model was developed to test the hydraulic implications of a sequence-stratigraphic model of the Dominguez Gap area and to assess the effects of water-management scenarios. The model is two-dimensional, vertical and follows an approximate flow line extending fromthe Pacific Ocean through the Dominguez Gap area. Results indicate that a newly identified fault system can provide a pathway for transport of seawater and that a stratigraphic boundary located between the Bent Spring and Upper Wilmington sequences may control the vertical movement of seawater. Three 50-year water-management scenarios were considered: (1) no change in water-management practices; (2) installation of a slurry wall; and (3) raising inland water levels to 7.6m above sea level. Scenario 3 was the most effective by reversing seawater intrusion. The effects of an instantaneous 1-m sealevel rise were also tested using water-management scenarios 1 and 3. Results from two 100-year simulations indicate that a 1-m sea-level rise may accelerate seawater intrusion for scenario 1; however, scenario 3 remains effective for controlling seawater intrusion.

Strawberry Case Study: What If Farmers Had to Pay for Water?

New York Times | December 29th, 2023

While American farmers elsewhere have watered their crops by freely pumping the groundwater beneath their land, growers in Pajaro must pay hefty fees for irrigation water

While American farmers elsewhere have watered their crops by freely pumping the groundwater beneath their land, growers in Pajaro must pay hefty fees for irrigation water — making it one of the most expensive places to grow food in the country, if not the world. The cost: Up to $400 per acre-foot, a standard measurement equal to water covering one acre, one foot deep. The fees bring in $12 million a year, which is used to recycle, restore and conserve the region’s groundwater.

Streamflow depletion by wells—Understanding and managing the effects of groundwater pumping on streamflow

U.S. Geological Survey (USGS) | December 21st, 2012

Groundwater provides drinking water for millions of Americans and is the primary source of water to irrigate cropland in many of the Nation’s most productive agricultur

Groundwater provides drinking water for millions of Americans and is the primary source of water to irrigate cropland in many of the Nation’s most productive agricultural regions. Withdrawals in many aquifers throughout the United States have led to significant groundwater-level declines, resulting in growing concerns about sustainability and higher pumping costs. The U.S. Geological Survey’s (USGS) Groundwater Resources Program has been instrumental in documenting groundwater declines and in developing groundwater-flow models for use in sustainably managing withdrawals. Groundwater withdrawals also can lead to a reduction in streamflow, affecting both human uses and ecosystems. The first clear articulation of the effects of groundwater pumping on surface water was by the well-known USGS hydrologist C.V. Theis. In a paper published in 1940 entitled "The Source of Water Derived from Wells," Theis pointed out that pumped groundwater initially comes from reductions in aquifer storage. As pumping continues, the effects of groundwater withdrawals can spread to distant connected streams, lakes, and wetlands through decreased rates of discharge from the aquifer to these surface-water systems. In some settings, increased rates of aquifer recharge also occur in response to pumping, including recharge from the connected surface-water features. Associated with this decrease in groundwater discharge to surface waters is an increased rate of aquifer recharge. Pumping-induced increased inflow to and decreased outflow from an aquifer is now called "streamflow depletion" or "capture." Groundwater discharge is a significant component of streamflow, with groundwater contributing as much as 90 percent of annual streamflow volume in some parts of the country. In order to effectively manage the entire water resource for multiple competing uses, hydrologists and resource managers must understand the effects (magnitude, timing, and locations) of ground-water pumping on rivers, streams, springs, wetlands, and groundwater-dependent vegetation. This circular, developed as part of the USGS Groundwater Resources Program, presents concepts relating to streamflow depletion, methods for quantifying depletion, and common misconceptions regarding depletion. Approaches for monitoring, understanding, and managing streamflow depletion also are described. The report is written for a wide audience interested in the development, management, and protection of the Nation's water resources. The Groundwater Resources Program provides objective scientific information and develops the interdisciplinary understanding necessary to assess and quantify the availability of the Nation's groundwater resources. Detailed assessments of regional aquifers have been completed in seven of the Nation’s major aquifers, with several additional assessments ongoing or planned. The research and understanding developed through this program for issues such as streamflow depletion can provide the Nation’s water-resource managers with the tools and information needed to manage this important natural resource.

Study of Potential for Groundwater Contamination from Past Dry Cleaner Operations in Santa Clara County

Santa Clara Valley Water District | September 20th, 2007

The threat of groundwater contamination posed by dry cleaning operations is primarily a legacy issue. Dry cleaners today have greatly improved usage and handling of solve

The threat of groundwater contamination posed by dry cleaning operations is primarily a legacy issue. Dry cleaners today have greatly improved usage and handling of solvents. Perchloroethylene (PCE) remains the most prevalent solvent used for dry cleaning. Dry cleaning machinery has evolved substantially and is designed to be leak-proof, air-tight, and to minimize waste generation. Dry cleaning facilities are subject to multiple permits, and are regularly inspected. A few dry cleaners have switched to “environmentally safe” solvents in their operations. Failures and operator error can nonetheless occur, representing a minor continuing threat to groundwater. The greater threat to groundwater quality is from past dry cleaning operations from as long as 50 years ago, a threat which remains significant today. This study catalogued the locations and years of operations for current and former dry cleaning operations in Santa Clara County. Past dry cleaner operational practices, solvent usage, groundwater subbasin vulnerability, and municipal supply well vulnerability are explored to develop a system to rank the relative risk of groundwater contamination from dry cleaner solvent releases. The systematic ranking of the threat posed by dry cleaners provides a means of prioritizing dry cleaning sites for further investigation. The ranking system will be useful to regulatory agencies for determining which cases warrant more aggressive investigation and remediation.

Submittal of Report – Status Report on Implementation of the California Statewide Groundwater Elevation Monitoring Program Years 2012-2015

California Department of Water Resources (DWR) | April 1st, 2016

Senate Bill X7 6 (SBX7 6) (Chapter 1, Statutes of 2009) added provisions for groundwater monitoring to Division 6 of the Water Code (Water Code § 10920 et seq.). The bil

Senate Bill X7 6 (SBX7 6) (Chapter 1, Statutes of 2009) added provisions for groundwater monitoring to Division 6 of the Water Code (Water Code § 10920 et seq.). The bill authorized the Department of Water Resources (DWR) to establish permanent, locally managed, groundwater elevation monitoring and reporting for all 515 groundwater basins identified in DWR Bulletin 118, California’s Groundwater, as shown in Figure 1. Groundwater elevation data are foundational to improving the management and sustainability of California's groundwater resources. DWR developed the California Statewide Groundwater Elevation Monitoring (CASGEM) Program to implement SBX7 6. Water Code section 12924(c) requires DWR to report the status of the CASGEM Program to the Governor and Legislature by January 1, 2012, and thereafter in years ending in “5” or “0”. This report covers calendar years 2012 through 2015. The overall purpose of the CASGEM Program is to track seasonal and long-term groundwater elevation trends in groundwater basins statewide. The Water Code directs DWR to rely on, and build upon, the many established local agency groundwater monitoring and management efforts throughout the state. DWR works cooperatively with local agencies, referred to as CASGEM “Monitoring Entities,” to collect and maintain groundwater elevation data in a manner that is readily and widely available to the public. During 2010 and 2011, the first two years of the CASGEM Program, DWR focused its efforts on initiating the CASGEM Program and ensuring that Monitoring Entities would, by January 2012, be able to submit groundwater elevation data electronically.

Subsidence (2004-2009) in and near lakebeds of the Mojave River and Morongo groundwater basins, southwest Mojave Desert, California

U.S. Geological Survey (USGS) | July 1st, 2014

Subsidence: A critical challenge to Friant-Kern canal water deliveries

Friant Water Authority | January 17th, 2018

The Friant Water Authority is facing a critical challenge right now - one that has reduced our ability to deliver water to many Friant Division Contractor’s

The Friant Water Authority is facing a critical challenge right now - one that has reduced our ability to deliver water to many Friant Division Contractor’s by nearly 60%. It is a challenge that must be met today if we are to ensure our long-term commitment to delivering high-quality, dependable water, in the amounts needed by farmers and cities in the San Joaquin Valley.

Subsurface water flux in California's Central Valley and its source watershed from space geodesy

American Geophysical Union (AGU) | September 29th, 2022

We combine measurements from Global Positioning System positioning and Gravity Recovery and Climate Experiment gravity to infer change in water components in Central Vall

We combine measurements from Global Positioning System positioning and Gravity Recovery and Climate Experiment gravity to infer change in water components in Central Valley and its source watershed, the Sacramento-San Joaquin-Tulare River basin better than possible with either technique separately. We find that the Central Valley has lost groundwater from 2006 to 2021 at 2.2 ± 0.7 km 3/ yr (95% confidence limits follow the “±” sign), with 2/3 of the groundwater loss occurring in the southern part of the Valley. We estimate the seasonal recharge and loss of subsurface water in the Central Valley. Comparison to a model accounting for precipitation, evapotranspiration, and river water entering and leaving the Central Valley suggests that deep groundwater may be flowing from the Sierra Nevada mountains into the Central Valley.

Summary of Hydrologic Testing, Wellbore-Flow Data, and Expanded Water-Level and Water-Quality Data, 2011–15, Fort Irwin National Training Center, San Bernardino County, California

U.S. Geological Survey (USGS) | October 29th, 2019

In view of the U.S. Army’s historical reliance and plans to increase demands on groundwater to supply its operations at Fort Irwin National Training Center (NTC), Calif

In view of the U.S. Army’s historical reliance and plans to increase demands on groundwater to supply its operations at Fort Irwin National Training Center (NTC), California, coupled with the continuing water-level declines in some developed groundwater basins as a result of pumping, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army, evaluated the water resources, including water quality and potential groundwater supply, of undeveloped basins in the NTC. Previous work in the three developed groundwater basins—Langford, Bicycle, and Irwin—provided information to support water-resources management of those basins. During 2009–12, the USGS installed 41 wells at the NTC; 34 wells were at 14 single- or multiple-well monitoring sites, and 7 wells were long-screen test wells. The majority of the wells were installed in previously undeveloped or minimally developed groundwater basins (Cronise, Red Pass, the Central Corridor area, Superior, Goldstone, and Nelson Basins). During 2012–15, the USGS tested hydrologic properties at 32 wells in 8 basins to help characterize the aquifer system. This report presents data and analyses from core samples; slug tests and single-well aquifer tests; coupled measurements of wellbore flow, water levels, and water-quality constituents; and results from two-dimensional numerical modeling. This information provides a basis for developing and constraining basin-scale hydrogeologic framework and groundwater-flow models to further evaluate water resources in each groundwater basin.Core samples were tested for vertical saturated hydraulic conductivity, physical properties, and particle-size distribution. Vertical saturated hydraulic conductivities of the cores ranged from less than 0.00001 to 18.13 feet per day, and porosities ranged from 0.15 to 0.56. These physical properties and particle-size analyses indicate the high degree of heterogeneity of the hydrogeologic deposits penetrated by the boreholes. Horizontal hydraulic conductivities estimated from slug tests in 22 monitoring wells in 6 basins (Cronise, Central Corridor area, Goldstone, Langford, Bicycle, and Nelson Basins) ranged from less than 0.1 to 40 feet per day. Results of the aquifer tests at six test wells in the Goldstone, Nelson, and Superior Basins indicate hydraulic conductivities ranged from 0.37 to 66 feet per day; associated transmissivity values ranged from 130 to 28,000 feet squared per day. Wellbore-flow data, collected from the six test wells under unpumped and pumped conditions, generally showed downward movement of water. Flow data collected under unpumped conditions indicate groundwater entered the well through the upper part of the screened interval and exited to aquifer zones in the lower part of the screened interval at rates ranging from 1 to 3 gallons per minute. Flow data collected under pumping conditions show increased flow downward in the test wells, indicating higher yields from deeper aquifers. Water levels, measured periodically between 2011 and 2015, remained stable during this period in the majority of the wells measured since 2011, except at two monitoring sites in developed basins (Bicycle and Langford). Vertical hydraulic gradients were generally low throughout the NTC, but ranged from –0.0003 to 0.27 during the summer of 2015. Multiple-well monitoring sites in Bicycle, Central Corridor area, Cronise, Goldstone, Nelson, and Superior Basins, had downward vertical gradients.  Groundwater in wells in Nelson and Superior Basins, and wells BLA5, CCT1, and GOLD2 #2, was characterized as sodium-bicarbonate water, whereas groundwater from the remaining wells in Goldstone Basin was characterized as sodium-chloride water and Cronise Basin, and well LL04 was characterized by sodium-sulfate water. Total dissolved solids (TDS) ranged from 285 to 13,400 milligrams per liter (mg/L) TDS and chloride concentrations ranged from 19 to 1,030 mg/L chloride, with lowest concentrations of each in groundwater from Superior and Nelson Basins and highest concentrations in Cronise Basin. Nitrate plus nitrite as nitrogen ranged from less than 0.040 mg/L in groundwater from Cronise and Goldstone Basins to about 20 mg/L in Nelson Basin. Groundwater from wells in Nelson Basin was isotopically light, whereas groundwater samples from wells CRTH1, CRTH2, and LL04 were isotopically heavier and plotted along an evaporative trend line. No measurable tritium was detected in groundwater from 13 wells sampled in 2015, indicating that groundwater was recharged prior to 1952. Measured carbon-14 (14C) activities in groundwater from four wells sampled in 2015 ranged from about 7.9 to 23.5 percent modern carbon and had apparent (uncorrected) ages of 11,970–20,980 years. Arsenic concentrations were above the maximum contaminant level of 10 micrograms per liter in groundwater from all wells, except those in Goldstone Basin and the two deepest wells in Langford Basin (LL04); likewise, fluoride concentrations were above the California maximum contaminant level of 2 mg/L in groundwater from most wells, except those in Goldstone and Superior Basins, the middle well in Langford Basin, middle and deep wells in two locations in Cronise Basin, and two wells in Nelson Basin. Wellbore flow was simulated for each well by using an integrated-flow analysis tool, AnalyzeHOLE, to evaluate aquifer properties and heterogeneity. Horizontal layers in the model (hydrogeologic units) were defined by lithostratigraphic‐geophysical units, interpreted from lithologic and geophysical logs for each well, and were adjusted during calibration. The saturated hydraulic conductivities derived from the calibrated simulations ranged from less than 0.01 to 60 feet per day in Nelson, Goldstone, and Superior Basins.

Supporting sustainable groundwater management

California Agriculture (UCANR) | March 13th, 2018

Implementation of the 2014 Sustainable Groundwater Management Act is on schedule. The first phase, completed in 2017, created a new layer of local government —

Implementation of the 2014 Sustainable Groundwater Management Act is on schedule. The first phase, completed in 2017, created a new layer of local government — groundwater sustainability agencies. Now, these new agencies must prepare groundwater sustainability plans. These plans will lay out a basic reckoning for every overdrafted basin: without additional water to replace groundwater pumping or to recharge aquifers, there will be less available to produce food, supply homes and businesses, and ensure there is enough water for the environment.