Aquatic Life Study Final Report

San Joaquin Valley Drainage Authority | January 6th, 2016

Central Valley Salinity Alternatives for Long Term Sustainability (CV‐SALTS) is developing a comprehensive regulatory and programmatic approach to the management of sa

Central Valley Salinity Alternatives for Long Term Sustainability (CV‐SALTS) is developing a comprehensive regulatory and programmatic approach to the management of salt and nitrate in the Central Valley that is consistent with the State Recycled Water Policy (SRWP). This work is being carried out collaboratively with the Central Valley Regional Water Quality Control Board (Central Valley Water Board), the State Water Resources Control Board (State Water Board), the Central Valley Salinity Coalition and Stakeholders. As stated in the CV‐SALTS Strategy and Framework document, the strategy to fulfill the requirements of the SRWP is to adopt a Central Valley Salt and Nitrate Management Plan (SNMP) and revise the Basin Plans applicable to the Central Valley to facilitate implementation of the SNMP. This effort includes a technical review of the state of science with regards to the establishment of appropriate water quality objectives (WQO) to protect surface water beneficial uses. This Aquatic Life Study was undertaken to evaluate the technical basis for the establishment of salinity‐related WQOs to protect aquatic life in the Central Valley. The findings of this analysis will be considered by CV‐SALTS during development and adoption of the SNMP.

Basin-scale responses of groundwater-resource quality to drought and recovery, San Joaquin Valley, California

Hydrological Processes (Wiley) | April 15th, 2024

Groundwater-resource quality is assumed to be less responsive to drought compared to that of surface water due to relatively long transit times of recharge to drinking-su

Groundwater-resource quality is assumed to be less responsive to drought compared to that of surface water due to relatively long transit times of recharge to drinking-supply wells. Here, we evidence dynamic perturbations in aquifer pressure dynamics during drought and subsequent recovery periods cause dramatic shifts in groundwater quality on a basin scale. We used a novel application of time-series clustering on annual nitrate anomalies at >450 public-supply wells (PSWs) across California's San Joaquin Valley during 2000–22 to group subpopulations of wells with similar water-quality responses to drought. Additionally, we statistically evaluated the direction and magnitude of multi-constituent water-quality changes across the San Joaquin Valley using a broader dataset of >3000 PSWs with data during two select hydrologic stress periods representing an extreme drought (2012–16) and subsequent recovery (2016–19). Results of time-series clustering and stress-period change analyses corroborate a predominant regional response to pumping stress characterized by increased concentrations of anthropogenic constituents (nitrate, total dissolved solids) and decreased concentrations of geogenic constituents (arsenic, fluoride), which largely reversed during recovery. Cluster analysis also identified a secondary, less commonly occurring group of PSWs where nitrate decreased during drought, but explanatory factor analysis was not able to discern hydrogeologic drivers for these two divergent response patterns. Long-term tracer data support the hypothesis that the predominant regional signal of nitrate increase during drought is caused by enhanced capture of modern-aged groundwater by PSWs during periods of pumping stress, which can drive rapid changes in water quality on seasonal and multiannual timescales. Pumping-induced migration of modern, oxic groundwater to depth during drought may affect geochemical conditions in deeper portions of regional aquifers controlling the mobility of geogenic contaminants over the long term.

Bayesian nitrate source apportionment to individual groundwater wells in the Central Valley by use of elemental and isotopic tracers

American Geophysical Union (AGU) | July 31st, 2016

Groundwater quality is a concern in alluvial aquifers that underlie agricultural areas, such as in the San Joaquin Valley of California. Shallow domestic wells (less tha

Groundwater quality is a concern in alluvial aquifers that underlie agricultural areas, such as in the San Joaquin Valley of California. Shallow domestic wells (less than 150 m deep) in agricultural areas are often contaminated by nitrate. Agricultural and rural nitrate sources include dairy manure, synthetic fertilizers, and septic waste. Knowledge of the relative proportion that each of these sources contributes to nitrate concentration in individual wells can aid future regulatory and land management decisions. We show that nitrogen and oxygen isotopes of nitrate, boron isotopes, and iodine concentrations are a useful, novel combination of groundwater tracers to differentiate between manure, fertilizers, septic waste, and natural sources of nitrate. Furthermore, in this work, we develop a new Bayesian mixing model in which these isotopic and elemental tracers were used to estimate the probability distribution of the fractional contributions of manure, fertilizers, septic waste, and natural sources to the nitrate concentration found in an individual well. The approach was applied to 56 nitrate-impacted private domestic wells located in the San Joaquin Valley. Model analysis found that some domestic wells were clearly dominated by the manure source and suggests evidence for majority contributions from either the septic or fertilizer source for other wells. But, predictions of fractional contributions for septic and fertilizer sources were often of similar magnitude, perhaps because modeled uncertainty about the fraction of each was large. For validation of the Bayesian model, fractional estimates were compared to surrounding land use and estimated source contributions were broadly consistent with nearby land use types.

California regulation of agricultural runoff

American Bar Association (ABA) | November 1st, 2017

Agriculture in California is a multibillion dollar industry that produces more than half of the nation’s fruits, nuts, and vegetables. But this comes at a cost. Agricul

Agriculture in California is a multibillion dollar industry that produces more than half of the nation’s fruits, nuts, and vegetables. But this comes at a cost. Agriculture is the primary source of water pollution, with irrigation and rainfall sweeping excess fertilizers and pesticides off the fields into adjoining waters and, over time, leaching into groundwater. As a result, waterbodies—spanning roughly 8,000 miles of rivers and streams and 300,000 acres of lakes, bays, and wetlands—are impaired.

Central Valley Region Salt and Nitrate Management Plan

Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) | January 19th, 2017

Elevated salinity and nitrates in surface water and groundwater are increasing problems affecting much of California, other western states, and arid regions throughout th

Elevated salinity and nitrates in surface water and groundwater are increasing problems affecting much of California, other western states, and arid regions throughout the world. In California, as surface and groundwater supplies become scarcer, and as wastewater streams become more concentrated, salinity and nitrate impairments are occurring with greater frequency and magnitude. In 2006, the Central Valley Water Board, the State Water Board, and stakeholders began a joint effort to address salinity and nitrate problems in California’s Central Valley and adopt long-term solutions that will lead to enhanced water quality and economic sustainability. Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) is a collaborative basin planning effort aimed at developing and implementing a comprehensive salinity and nitrate management program. The goal of CV-SALTS is to maintain a healthy environment and a good quality of life for all Californians by protecting our most essential and vulnerable resource: WATER. In July 2008, the Central Valley Salinity Coalition (CVSC) was formed.  CVSC represents stakeholder groups working with the Board in the CV-SALTS effort.  Its purpose is to organize, facilitate and fund efforts needed to fulfill the goals of CV-SALTS.  CVSC coordinates the meetings of the CV-SALTS committees, maintains an independent web site, and manages the projects originating from this effort.  Information and materials regarding the stakeholder committees and other activity, including the meeting schedule, are posted on their website: www.cvsalinity.org. The Final SNMP for Central Valley Water Board Consideration was completed in December 2016. The Central Valley Water Board staff plans to release this version of the SNMP and all of its supporting attachments in January 2017 for a comment period so that the public has the opportunity to review the SNMP documentation before a general information workshop is held with the Central Valley Water Board, currently planned for March 2017.

Characterizing Nitrates in Central Coast Groundwater

Central Coast Groundwater Coalition (CCGC) | April 1st, 2016

The Central Coast Groundwater Coalition (CCGC) is a third-party cooperative groundwater monitoring program that was established for landowners/operators in the Ce

The Central Coast Groundwater Coalition (CCGC) is a third-party cooperative groundwater monitoring program that was established for landowners/operators in the Central Coast region as an alternative to the individual groundwater monitoring program. The cooperative program collects and synthesizes groundwater monitoring data on behalf of its members to fulfill requirements of the Irrigated Lands Regulatory Program. The Central Coast Regional Water Quality Control Board required that the CCGC characterize groundwater quality in the uppermost aquifer and identify and evaluate groundwater used for drinking water purposes. Specifically, the focus was on evaluating the spatial distribution of nitrate concentrations in ground- water basins used for drinking water and provide statistically-based estimates of where groundwater nitrate concentrations are likely to be above the maximum contaminant level (MCL) for nitrate.

Comparing Domestic and Public-Supply Groundwater Quality in the Northern San Joaquin Valley, 2019: California GAMA Priority Basin Project

U.S. Geological Survey (USGS) | June 5th, 2023

Analysis of construction data for wells included in the comparative assessment indicated that, although depth to top of perforations are comparable for domestic and publi

Analysis of construction data for wells included in the comparative assessment indicated that, although depth to top of perforations are comparable for domestic and public-supply wells in the Northern San Joaquin Valley (median depth about 60 meters [m]), public-supply wells have longer perforation intervals and extend to deeper parts of the aquifer system (exceeding 120 m) than domestic wells that typically draw exclusively from the shallower aquifer system in the upper 80 m of unconsolidated sediments. Analysis of the vertical and lateral distribution of constituents of interest (nitrate, fumigants, and arsenic) across domestic- and public-supply aquifers indicated that nitrate is prevalent in shallow aquifers throughout the Northern San Joaquin Valley but is potentially diluted by mixing with deeper, older groundwater at long-screened public-supply wells. Fumigants were prevalent in areas of urban and agricultural land use in the western part of the Northern San Joaquin Valley, particularly in areas near Lodi, California, but 1,2,3-TCP was more widespread than DBCP and was detected in shallow and deeper parts of the aquifer system, potentially because of its recalcitrance in groundwater and ability to be detected at low concentrations. Arsenic was most prevalent in the western part of the Northern San Joaquin Valley with proximity to deltaic sediments and was detected at high RCs in wells tapping shallow and deep parts of the aquifer system.

Comparison of potential drinking water source contamination across one hundred U.S. cities

Nature Portfolio (Springer Nature) | December 13th, 2021

Drinking water supplies of cities are exposed to potential contamination arising from land use and other anthropogenic activities in local and distal source watersheds. B

Drinking water supplies of cities are exposed to potential contamination arising from land use and other anthropogenic activities in local and distal source watersheds. Because water quality sampling surveys are often piecemeal, regionally inconsistent, and incomplete with respect to unregulated contaminants, the United States lacks a detailed comparison of potential source water contamination across all of its large cities. Here we combine national scale geospatial datasets with hydrologic simulations to compute two metrics representing potential contamination of water supplies from point and nonpoint sources for over a hundred U.S. cities. We reveal enormous diversity in anthropogenic activities across watersheds with corresponding disparities in the potential contamination of drinking water supplies to cities. Approximately 5% of large cities rely on water that is composed primarily of runoff from non-pristine lands (e.g., agriculture, residential, industrial), while four-fifths of all large cities that withdraw surface water are exposed to treated wastewater in their supplies.

Concentrations for total dissolved solids, arsenic, boron, fluoride, and nitrite-nitrate for wells sampled in the Mojave Water Agency Management Area

U.S. Geological Survey (USGS) | July 1st, 2001

CV SALTS Prioritization & Optimization Study Year 1 Progress Report

Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) | March 24th, 2023