Public Update for Drought Response Groundwater Basins with Potential Water Shortages and Gaps in Groundwater Monitoring

California Department of Water Resources (DWR) | June 30th, 2014

Year 2013 closed as the driest in recorded history for many areas of California. On January 17, 2014, Governor Brown signed a Proclamation of a State of Emergency in resp

Year 2013 closed as the driest in recorded history for many areas of California. On January 17, 2014, Governor Brown signed a Proclamation of a State of Emergency in response to the drought. This Public Update addresses Order #11 of the Governor’s Proclamation and provides information regarding groundwater basins with potential water shortages and gaps in groundwater monitoring. Groundwater is a vital resource in California providing close to 60 percent of the state’s water supply in a dry year. Drought conditions typically result in an increase of groundwater well activity and pumping to compensate for water supply shortages. Increased groundwater pumping can lead to adverse conditions including dry wells, subsidence, decreased water quality, saline intrusion, and stream depletion. Evaluation of available data produced the following: Groundwater levels have decreased in nearly all areas of the state since spring 2013, and more notably since spring 2010. Since spring 2008, groundwater levels have experienced all-time historical lows (for period of record) in most areas of the state and especially in the northern portion of the San Francisco Bay Hydrologic Region, the southern San Joaquin Valley, and also for the South Lahontan and South Coast hydrologic regions. In many areas of the San Joaquin Valley, recent groundwater levels are more than 100 feet below previous historical lows. The greatest concentration of recently deepened wells is in the fractured bedrock foothill areas of Nevada, Placer, and El Dorado counties. The Kaweah and Kings subbasins have the greatest numbers of deepened wells in an alluvial groundwater basin. Thirty-six alluvial groundwater basins that have a high degree of groundwater use and reliance may possess greater potential to incur water shortages as a result of drought. The basins exist in the North Coast, Central Coast, Sacramento River, Tulare Lake, and South Coast hydrologic regions. Of California’s 515 alluvial groundwater basins, 169 are fully or partially monitored under the California Statewide Groundwater Elevation Monitoring (CASGEM) Program. Forty of the 126 High and Medium priority basins are not monitored under CASGEM. There are significant CASGEM groundwater monitoring data gaps in the Sacramento, San Joaquin River, Tulare Lake, Central Coast, and South Lahontan hydrologic regions. Although there are 4,122 CASGEM wells and 39,429 Voluntary wells in the Water Data Library groundwater level database, gaps in groundwater monitoring persist. Several areas of the state lack a current groundwater management plan that addresses all related requirements of the California Water Code. DWR is contracting with National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory for use of satellite-based radar data to measure subsidence in the Sacramento and San Joaquin valleys. NASA, the U.S. Geological Survey, and U.S. Department of Agriculture are developing an automated system for estimating fallowed agricultural acreage.

Public Update for Drought Response: Groundwater Basins with Potential Water Shortages, Gaps in Groundwater Monitoring, Monitoring of Land Subsidence, and Agricultural Land Fallowing

California Department of Water Resources (DWR) | November 25th, 2014

California’s Water Year 2014 (October 1, 2013 through September 30, 2014) was one of the driest in decades and followed two consecutive dry years throughout the state.

California’s Water Year 2014 (October 1, 2013 through September 30, 2014) was one of the driest in decades and followed two consecutive dry years throughout the state. Water year 2014 was the fourth driest year on record after 1924, 1931, and 1977, based on the Sacramento Valley water year index, and the second driest year on record after 1977, based on the San Joaquin Valley water year index. On January 17, 2014, Governor Brown signed a Proclamation of a State of Emergency in response to the drought. In accordance with the proclamation, the Department of Water Resources (DWR) prepared Public Update for Drought Response, Groundwater Basins with Potential Water Shortages and Gaps in Groundwater Monitoring, dated April 30, 2014. On April 25, 2014, the governor issued a second emergency proclamation to strengthen the state’s ability to manage water and habitat effectively in drought conditions and called on all Californians to redouble their efforts to conserve water. In accordance with Order #11 of the April proclamation, this report provides additional and expanded information on groundwater basins with potential water shortages, gaps in groundwater monitoring, monitoring of land subsidence, and agricultural land fallowing.

Pulse Flows Component of the Water Storage Investment Program Groundwater Projects Supplemental Environmental Impact Report

California Department of Water Resources (DWR) | July 30th, 2024

This final supplemental environmental impact report (Final SEIR) has been prepared for the Pulse Flows Component of the Water Storage Investment Program (WSIP) Groundwate

This final supplemental environmental impact report (Final SEIR) has been prepared for the Pulse Flows Component of the Water Storage Investment Program (WSIP) Groundwater Projects (Pulse Flows Component). The Final SEIR is a supplement to three certified environmental impact reports (EIRs) prepared pursuant to the California Environmental Quality Act (CEQA) for three independent WSIP projects (referred to herein as the “WSIP Groundwater Projects”): (1) the Chino Basin Program, (2) the Kern Fan Groundwater Storage Project (Kern Fan), and (3) the Willow Springs Water Bank Project (Willow Springs).

Pumping and Ground-Water Storage Depletion in Las Vegas Valley, Nevada, 1955-1974

U.S. Geological Survey (USGS) | July 1st, 1976

Pumping for the masses: evolution of groundwater management in metropolitan Los Angeles

Geo Journal (Springer) | August 7th, 2015

Groundwater supports many aspects of human life. In cities, groundwater can provide a cost-effective source of water for drinking and industrial uses, while groundwater b

Groundwater supports many aspects of human life. In cities, groundwater can provide a cost-effective source of water for drinking and industrial uses, while groundwater basins provide storage. The role of groundwater in a city’s water supply tends to change over time. In the Los Angeles metropolitan area, groundwater is critical. Over decades, users in the region’s many basins allocated annual pumping rights to groundwater among users through adjudications. These rights were determined through collective processes over decades, which contributed to the complex array of public and private organizations involved in water management. The rights also continue to evolve. We analyzed changes in the distribution of groundwater rights over time for adjudicated basins in Southern Los Angeles County. Results indicate that groundwater rights are increasingly: (1) controlled or regulated by public institutions and municipalities, and (2) consolidated among larger users. Yet, both the percentage of total supplies provided by groundwater, as well as the distribution of groundwater rights, varies widely among cities and communities throughout Los Angeles. As metropolitan Los Angeles faces reduced water imports and emphasizes local water reliance, access to pumping rights and storage capacity in groundwater basins will become even more vital. We discuss implications of our results for future urban water management.

Pure Water Soquel Groundwater Model Simulation Results

Soquel Creek Water District | June 22nd, 2018

This technical memorandum discusses model simulation groundwater levels, groundwater budget, and particle tracking results to support the Environmental Impact Rep

This technical memorandum discusses model simulation groundwater levels, groundwater budget, and particle tracking results to support the Environmental Impact Report of the Pure Water Soquel project involving replenishment of advanced purified recycled water within Soquel Creek Water District’s (SqCWD’s) service area. Six model simulations have been run using the calibrated GSFLOW model for the Santa Cruz Mid- County Basin (the Basin) where SqCWD’s service area is located. These simulations have different pumping and active replenishment distributions, as follows: Two Projected Existing Conditions (No Project) simulations with SqCWD’spumping distribution reflecting future demand without additional replenishment at proposed recharge wells. Two Project simulations with SqCWD’s pumping distribution reflecting future demand and pumping re-distribution with the addition of replenishment at the Monterey and Cabrillo College Dr. sites (referred to as the Cabrillo-Monterey simulations). These simulations also represent potential replenishment at the Twin Lakes Church site instead of one of the two Cabrillo College Dr. sites. The Twin Lakes Church site is approximately 500-750 feet to the west of the Cabrillo College Dr. sites. Two Project simulations with the same pumping distribution as the Cabrillo- Monterey simulations, but with replenishment at the Monterey and Willowbrook sites (referred to as the Monterey-Willowbrook simulations).Simulation groundwater levels are evaluated for the following effects: Comparison of groundwater levels at coastal monitoring wells to protective elevations estimated to prevent seawater intrusion from further occurring in groundwater supply aquifers. Groundwater levels in the recharge wells to assess whether model results are consistent with estimated capacities for the well, recognizing that site specific testing will be needed to confirm recharge well capacities. Groundwater levels at nearby wells to evaluate effects on operation of those municipal, private, and institutional wells.Simulation groundwater budgets are evaluated for following effects: • Flows entering and leaving the Basin, including flows to and from groundwater in storage and flows offshore to prevent seawater intrusion. • Flows between groundwater and surface water. This memo does not include results for a Cumulative simulation. Information from the City of Santa Cruz to define its Aquifer Storage and Recovery project to be cumulative with Pure Water Soquel is not available or developed at this time. This memo includes results from particle tracking based on the above simulations performed to support the Salt and Nutrient Anti-degradation Study and permitting of the recharge wells. This involves particle tracking of simulated purified, replenishment water to evaluate the fate of the water as it travels in subsurface aquifers. Particle tracking is also used to evaluate travel times of purified, replenishment water, which requires refined analysis near the recharge wells. A scope to superimpose analytic element solutions for recharge and nearby extraction wells onto GSFLOW results to facilitate travel time calculations was approved by SqCWD Board December 18, 2017 and results should be forthcoming in July 2018.

Putting Adaptive Management into Practice: Incorporating Quantitative Metrics into Sustainable Groundwater Management

Stanford University | March 4th, 2019

Groundwater is a critical resource in California, serving as a reserve during droughts that are expected to be increasingly frequent and severe as climate change progres

Groundwater is a critical resource in California, serving as a reserve during droughts that are expected to be increasingly frequent and severe as climate change progresses. Adaptive management – revising management practices based on monitoring of progress toward pre-established quantitative metrics of performance – is widely viewed as an effective approach to managing water and other natural resources under conditions of uncertainty. However, linking performance metrics effectively with decision-making processes is often challenging, requiring careful consideration of institutional factors that may limit an agency’s ability to act based on new information. Governance arrangements that enable adaptive management must balance the need for flexibility as conditions change with a preference among water users for stable rules. The Sustainable Groundwater Management Act (SGMA) of 2014 – California’s first statewide framework for managing groundwater – incorporates many elements of adaptive management, including requirements to manage groundwater according to quantitative metrics of performance. Under regulations guiding the development of Groundwater Sustainability Plans (GSPs), newly formed Groundwater Sustainability Agencies (GSAs) must define measurable objectives, minimum thresholds and interim milestones to eliminate six “undesirable results” by 2040 or 2042, depending upon the basin. Yet, the creation of these metrics alone will be insufficient to achieve sustainable management of California’s groundwater; institutional arrangements must support their use to guide management actions. To provide insight into the design and use of metrics as guides to decision-making, this report draws upon the experiences of four special act districts that had authority to manage groundwater prior to SGMA. These include two primarily urban water agencies, Santa Clara Valley Water District (SCVWD) and Zone 7 Water Agency (Zone 7) and two agencies with significant pumping for agricultural use, Fox Canyon Groundwater Management Agency (FCGMA) and Pajaro Valley Water Management Agency (PVWMA). This report analyzes how these agencies used quantitative metrics in their groundwater management plans prior to SGMA and identifies institutional factors that constrained or enabled the adjustment of management actions in response to changing conditions during the 2012-2016 drought. Although the metrics employed by these agencies differ from those required under GSP regulations, these agencies’ experiences still offer important insights for GSAs seeking to develop metrics and integrate them into decision making.

Quality of Groundwater Used for Domestic Drinking-Water Supply in the Coachella Valley, 2020

U.S. Geological Survey (USGS) | January 13th, 2023

Quality of groundwater used for domestic supply in the eastern Sacramento Valley and adjacent foothills, California

U.S. Geological Survey (USGS) | November 1st, 2024

More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domes

More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domestic and small-system drinking-water supply wells in the eastern Sacramento Valley and adjacent foothills where more than 25,000 residents are estimated to use privately owned domestic wells. Study results show that inorganic and organic constituents in groundwater were present above regulatory (maximum contaminant level, MCL) benchmarks for public drinking-water quality in 8 and 3 percent, respectively, of the aquifer area used for domestic drinking-water supply. The only inorganic constituent detected above regulatory benchmarks was arsenic. The only organic constituent exceeding regulatory benchmarks was the fumigant 1,2,3-trichloropropane (1,2,3-TCP). Three additional organic constituents— the disinfection by-product chloroform, the gasoline oxygenate methyl tert-butyl ether (MTBE), and the solvent tetrachloroethene (PCE)—were detected at low concentrations below one-tenth of regulatory benchmarks in 34, 10, and 10 percent of domestic groundwater resources, respectively. Total dissolved solids (TDS), iron, and manganese exceeded non-regulatory aesthetic guidelines for drinking water in 5, 10, and 26 percent of domestic groundwater resources, respectively. Per- and polyfluoroalkyl substances (PFASs) were detected in 29 percent of domestic groundwater resources, with 5 percent exceeding the recently enacted (April 2024) U.S. Environmental Protection Agency MCLs. Total coliform and enterococci bacteria were detected in 13 and 8 percent of domestic groundwater resources, respectively. Redox sensitive constituents in this study included arsenic, manganese, nitrate, and iron. In the lower elevation portions of the eastern Sacramento Valley study area, reducing conditions in groundwater aquifers promote elevated arsenic, iron, and manganese, and conversely lower concentrations of nitrate. The presence of the volatile organic compound (VOC) 1,2,3-TCP was related to its past history in select agricultural land uses (on orchards or vineyards) in the Sacramento Valley; however, unlike in the San Joaquin Valley where orchards and vineyards are more common, its detection frequency was low (only detected in one well in this study). Chloroform was frequently detected in this study at low levels. Chloroform is a disinfection byproduct commonly found in domestic wells treated by shock chlorination. The solvent PCE is among the most frequently detected VOCs in groundwater, which is primarily related to its long history of use and its persistence in groundwater in oxic conditions. The gasoline oxygenate MTBE was a contaminant introduced to groundwater through atmospheric exchange when it was used as a fuel additive to decrease smog inducing emissions from vehicles. Its occurrence in groundwater at low levels is expected and makes it a potentially useful tracer of relatively recent recharge water being withdrawn from wells. The PFASs are anthropogenic chemicals with hundreds of uses, and they have been incorporated into many different products, processes, and applications worldwide. Like MTBE, the occurrence of PFASs in groundwater may be in part due to atmospheric exchange, but there are several other pathways that contribute PFASs to the environment.

Quality of Groundwater Used for Domestic Supply in the Modesto, Turlock, and Merced Subbasins of the San Joaquin Valley, California

U.S. Geological Survey (USGS) | January 6th, 2023

More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domes

More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domestic and small-system drinking-water supply wells in the Modesto, Turlock, and Merced subbasins of the San Joaquin Valley where more than 78,000 residents are estimated to use privately owned domestic wells. Results indicate that inorganic and organic constituents in groundwater were respectively present above regulatory (maximum contaminant level, MCL) benchmarks for public drinking-water quality in 37 percent and 9 percent of the aquifer area used for domestic drinking-water supplies (herein, “domestic groundwater resources”). The most prevalent inorganic constituents exceeding regulatory benchmarks were nitrate, uranium, and arsenic. The only organic constituents exceeding regulatory benchmarks were the fumigant constituents 1,2,3-trichloropropane (1,2,3-TCP) and 1,2-dibromo-3-chloropropane (DBCP), but the herbicides atrazine and simazine were detected at low concentrations below one-tenth of regulatory benchmarks in 30 percent of domestic groundwater resources. Total dissolved solids (TDS) and manganese exceeded aesthetic-based (secondary maximum contaminant level [SMCL]) benchmarks for drinking water in 3 percent and 13 percent of domestic groundwater resources, respectively. Per- and polyfluoroalkyl substances (PFAS) were detected in 23 percent of domestic groundwater resources, with 4 percent exceeding California state notification or response levels for specific compounds. Total coliform bacteria were detected in 20 percent of domestic groundwater resources. Elevated concentrations of nitrate, uranium, TDS, and pesticides (fumigant constituents and herbicides) are related to agricultural land use and were typically present at shallow depths up to 75 meters below land surface. Agriculturally derived constituents were detected in wells screened below the Corcoran Clay Member of the Tulare Formation (herein, “Corcoran Clay”) in the southeastern part of the study area, where the Corcoran Clay tends to be shallower and thinner than in areas to the northwest. Nitrate, uranium, and TDS were most prevalent in the northwest part of the study area proximal to the valley trough where soils are poorly drained and agricultural land uses are predominantly grain, alfalfa, and dairy farms. Pesticides tended to occur in groundwater below coarse-grained surficial deposits and within a northwest to southeast trending band along the eastern extent of the Corcoran Clay that typically demarcates the western extent of well-drained soils associated with perennial orchard crops. Elevated concentrations of arsenic tended to occur west of this band in reducing groundwater but also sometimes co-occurred with elevated nitrate in oxic groundwater, most likely because of geochemical conditions in agriculturally affected groundwater that can enhance the mobility of arsenic from aquifer sediments.