Quality of Groundwater Used for Domestic Supply in the Northern San Joaquin Valley, California

U.S. Geological Survey (USGS) | July 28th, 2021

 Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Moni

 Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project (PBP) of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and provides increased public access to groundwater-quality information. Private domestic and small-system drinking-water wells in the Northern San Joaquin Valley (NSJV) were the target for this assessment. These wells tend to pump water from shallower parts of alluvial aquifers compared to deeper, long-screened public-supply wells in the region. 

Quality of Groundwater Used for Public Supply in the Continental United States: A Comprehensive Assessment

American Chemical Society (ACS) | October 21st, 2022

Quantifying anthropogenic contributions to century-scale groundwater salinity changes, San Joaquin Valley, California, USA

Science of the Total Environment (Elsevier) | June 15th, 2018

Total dissolved solids (TDS) concentrations in groundwater tapped for beneficial uses (drinking water, irrigation, freshwater industrial) have increased on average by abo

Total dissolved solids (TDS) concentrations in groundwater tapped for beneficial uses (drinking water, irrigation, freshwater industrial) have increased on average by about 100 mg/L over the last 100 y ears in the San Joaquin Valley, California (SJV). D uring this period land use in the SJV changed from natural vegetation and dryland agriculture to dominantly irrigated agriculture with growing urban areas. Century-scale salinity trends were evaluated by comparing TDS concentrations and major ion compositions of groundwater from wells sampled in 1910 (Historic) to data from wells sampled in 1993 –2015 (Modern). TDS concentrations in subregions of the SJV, the southern (SSJV), western (WSJV), northeastern (NESJV), and southeastern (SESJV) were calculated using a cell-declustering method. TDS concentrations increased in all regions, with the greatest increases found in the SSJV and SESJV. Evaluation of the Modern data from the NESJV and SESJV found higher TDS concentrations in recently recharged (post-1950) groundwater from shallow (b50 m) wells surrounded predominantly by agricultural land uses, while premodern (pre-1950) groundwater from deeper wells, and recently recharged groundwater from wells surrounded by mainly urban, natural, and mixed land uses had lower TDS concentrations, approaching the TDS concentrations in the Historic groundwater. For the NESJV and SESJV, inverse geochemical modeling with PHREEQC indicated that weathering of primary silicate minerals accounted for the majority o f the increase in TDS concentrations, contributing more than nitrate from fertilizers and sulfate from soil amendments combined. Bicarbonate showed the greatest increase among major ions, resulting from enhanced silicate weathering due to recharge of irrigation water enriched in CO2 during the growing season. The results of this study demonstrate that large anthropogenic changes to the hydrologic regime, like massive development of irrigated agriculture in semi-arid areas like the SJV, can cause large changes in groundwater quality on a regional scale.

Regional nitrate and pesticide trends in ground water in the eastern San Joaquin Valley, California

American Society of Agronomy (ASA) | September 18th, 2008

Protection of ground water for present and future use requires monitoring and understanding of the mechanisms controlling long-term quality of ground water. In this stu

Protection of ground water for present and future use requires monitoring and understanding of the mechanisms controlling long-term quality of ground water. In this study, spatial and temporal trends in concentrations of nitrate and pesticides in ground water in the eastern San Joaquin Valley, California, were evaluated to determine the long-term effects of agricultural and urban development on regional ground-water quality. Trends in concentrations of nitrate, the nematocide 1,2-dibromo-3-chloropropane, and the herbicide simazine during the last two decades are generally consistent with known nitrogen fertilizer and pesticide use and with the position of the well networks in the regional ground-water fl ow system. Concentrations of nitrate and pesticides are higher in the shallow part of the aquifer system where domestic wells are typically screened, whereas concentrations are lower in the deep part of the aquifer system where public-supply wells are typically screened. Attenuation processes do not seem to significantly affect concentrations. Historical data indicate that concentrations of nitrate have increased since the 1950s in the shallow and deep parts of the aquifer system. Concentrations of nitrate and detection of pesticides in the deep part of the aquifer system will likely increase as the proportion of highly affected water contributed to these wells increases with time. Because of the time of travel between the water table and the deep part of the aquifer system, current concentrations in public-supply wells likely reflect the effects of 40- to 50-year-old management practices.

Responses of drinking water bulk and biofilm microbiota to elevated water age in bench-scale simulated distribution systems

Biofilms and Microbiomes (Nature) | January 22nd, 2024

Safe Drinking Water Plan for California

California State Water Resources Control Board (SWRCB) | June 9th, 2015

In 1993, the California Department of Health Services (CDHS) (now the California Department of Public Health (CDPH) submitted to the Legislature the report entitled, "Dri

In 1993, the California Department of Health Services (CDHS) (now the California Department of Public Health (CDPH) submitted to the Legislature the report entitled, "Drinking Water into the 21st Century: Safe Drinking Water Plan for California" (1993 Plan). In 1996, the California Legislature enacted Senate Bill (SB) 1307 (Chapter 755, Statutes of 1996). SB 1307 amended Health and Safety (H&S) Code Section 116355 to require a periodic update of the original Plan. The issues that were to be addressed were essentially the same as those included in the 1993 Plan. CDPH assembled a team of experts that conducted extensive reviews and analyses, resulting in a draft plan that included an overview of drinking water regulation, reviews and plans for drinking water quality/monitoring and threats, treatment technologies, funding aspects and financial assistance, and a focus on the challenges faced by small drinking water systems. Following the July 1, 2014 transition of the Drinking Water Program to the State Water Board, the draft plan’s recommendations and implementation plan has been enhanced based on the synergies and resources resulting from incorporation of the program into the State Water Board.  California continues to be dependent on a mixture of surface water and groundwater supplies for drinking water. The degree to which each type of supply is used in a given year is dependent upon the region of the state, water needs, water resource availability, and climatologic conditions within the state. During periods of normal to high rainfall, surface water sources make up a higher percentage of the overall drinking water supplies across the state. However, during periods of lower than average rainfall, use of groundwater increases and surface water supplies are strained. As California’s population has grown since the 1993 Plan was published, the demand on the State’s limited water resources have increased. To meet this demand, many public water systems (PWS) have promoted conservation measures as well as looked to other potential sources of supply such as recycled water and desalination. Mirroring the regulatory scope of the Division of Drinking Water, the scope of this Plan focuses on the state’s public water systems (PWS), as defined in Health and Safety Code 116275(h). These are systems that either have (a) 15 or more service connections or (b) systems that serve at least 25 individuals daily at least 60 days out of the year. There are currently more than 7,600 PWS in the state. This is a significant reduction from the more than 10,000 that were in existence in 1993.  However, California’s population has grown from approximately 29 million to over 38 million. Of those 7,600 PWS, approximately seven percent serve communities with more than 10,000 service connections (approximately 33,000 people). The majority of PWS serve smaller communities with more than 63 percent of PWS serving communities with less than 200 service connections (approximately 660 people). Many of the small PWS are challenged by lack of technical, managerial, and financial (TMF) capacity; many do not serve drinking water that meets standards (“safe drinking water”). In 2012, California became the first state to enact a Human Right to Water law, AB 685 (Chapter 524, Statutes of 2012). Public policy continues to be focused on the right of every human being to have safe, clean, affordable, and accessible water adequate for human consumption, cooking, and sanitation. Water supply, contaminants, costs of treatment and distribution systems, the number and nature of small PWSs, especially in disadvantaged communities, and many other factors will continue to challenge progress in addressing the Human Right to Water. The State Water Board is committed to actively pursuing initiatives to address the Human Right to Water, beginning with the state’s residents who are served by PWS but who do not receive safe drinking water.

Safe Drinking Water Plan for California: Report to the Legislature in Compliance with Health and Safety Code Section 116365

California State Water Resources Control Board (SWRCB) | June 8th, 2015

The State Water Board recognizes that to fulfill the Human Right to Water in California, every resident should have access to affordable, safe drinking water regardless

The State Water Board recognizes that to fulfill the Human Right to Water in California, every resident should have access to affordable, safe drinking water regardless of the water system size. Provided data become available on this topic, in a future update of the Safe Drinking Water Plan the Water Board could expand the scope to include systems below 15 service connections, but to do that would require new and expanded authority, significantly more resources, as well as commitment and involvement of other local and state agency partners. At this time, this report contains 32 practical recommendations in 9 areas that would expand the State Water Board’s efforts to bring a greater number of systems into compliance and contribute to realizing the Human Right to Water in California. Each chapter provides a background discussion covering the areas mandated by the Legislature including a description of problems and issues and a set of conclusions and recommendations with the basis and justification for them. A detailed five-year implementation plan addressing the major recommendations is provided in Appendix 10.

Salinity Effects on MUN‐Related Uses of Water

Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) | December 1st, 2016

Purpose: Summarize current state of knowledge regarding the effects of elevated conductivity, salinity or TDS and hardness on drinking water supply

Purpose: Summarize current state of knowledge regarding the effects of elevated conductivity, salinity or TDS and hardness on drinking water supply and other domestic purposes for water use. Identify/summarize unique concerns related to specific ions (e.g. sodium, chloride, boron, etc.).

San Fernando Groundwater Basin Remediation Program

Los Angeles Department of Water & Power (LADWP) | January 1st, 2018

San Gabriel Valley Superfund Sites Progress Updates

U.S. Environmental Protection Agency (EPA) | May 31st, 2021