Lake Tahoe Nearshore Water Quality Protection Plan

California State Water Resources Control Board (SWRCB) | November 6th, 2014

In October 2013, the Desert Research Institute, UC Davis, and University of Nevada at Reno released the Lake Tahoe Nearshore Evaluation and Monitoring Framework Report (R

In October 2013, the Desert Research Institute, UC Davis, and University of Nevada at Reno released the Lake Tahoe Nearshore Evaluation and Monitoring Framework Report (Report) (NeST 2013). The Report presents a conceptual understanding of nearshore environment processes, assesses the heterogenic nature of the nearshore, highlights the lack of data available to characterize the environmental status of the Lake Tahoe nearshore, and emphasizes that current agency implementation efforts will benefit the nearshore environment. This Lake Tahoe Nearshore Water Quality Protection Plan (Plan) outlines the Lahontan Regional Water Quality Control Board’s (Regional Water Board) response to the changes in the Lake Tahoe nearshore environment as informed by the Report. Based on the Report findings and recommendations, the Regional Water Board will proceed with the following actions: (1) continue implementing programs that benefit nearshore environmental quality; (2) establish and implement an integrated nearshore monitoring plan to track change in the nearshore environment and track pollutant inputs to the nearshore; (3) evaluate localized “hotspots” where nearshore change has been documented and assess causes of observed degradation; (4) investigate climate change influence on nearshore water quality; and (5) assess the need for revised or new water quality standards to protect nearshore water quality. In establishing and maintaining nearshore water quality protection policies, the Water Board will continue to coordinate with other government agencies and the public. Because available resources are insufficient to fully implement all recommendations, a dedicated annual funding source must be found to adequately protect and enhance Lake Tahoe’s precious nearshore. The Plan elements and funding needs are presented in Attachment 1. The Plan also serves as response to a Legislative request in the 2012-2013 Budget Act specific to the Water Board’s approach to the nearshore.

Land Subsidence in the Southwestern Mojave Desert, California, 1992–2009

U.S. Geological Survey (USGS) | July 8th, 2017

Groundwater has been the primary source of domestic, agricultural, and municipal water supplies in the southwestern Mojave Desert, California, since the early 1900s. Incr

Groundwater has been the primary source of domestic, agricultural, and municipal water supplies in the southwestern Mojave Desert, California, since the early 1900s. Increased demands on water supplies have caused groundwater-level declines of more than 100 feet (ft) in some areas of this desert (fig. 2 inset) between the 1950s and the 1990s (Stamos and others, 2001; Sneed and others, 2003). These water-level declines have caused the aquifer system to compact, resulting in land subsidence. Differential land subsidence (subsidence occurring at different rates across the landscape) can alter surface drainage routes and damage surface and subsurface infrastructure. For example, fissuring across State Route 247 at Lucerne Lake (fig. 2) has required repairs as has pipeline infrastructure near Troy Lake. Land subsidence within the Mojave River and Morongo Groundwater Basins of the southwestern Mojave Desert has been evaluated using InSAR, ground-based measurements, geology, and analyses of water levels between 1992 and 2009 (years in which InSAR data were collected). The results of the analyses were published in three USGS reports— Sneed and others (2003), Stamos and others (2007), and Solt and Sneed (2014). Results from the latter two reports were integrated with results from other USGS/ MWA cooperative groundwater studies into the broader scoped USGS Mojave Groundwater Resources Web site (http://ca.water.usgs.gov/mojave/). This fact sheet combines the detailed analyses from the three subsidence reports, distills them into a longer-term context, and provides an assessment of options for future monitoring.

Land subsidence, groundwater levels, and geology in the Coachella Valley, California, 1993-2010

U.S. Geological Survey (USGS) | June 15th, 2014

Land subsidence associated with groundwater-level declines has been investigated by the U.S. Geological Survey in the Coachella Valley, California, since 1996. Groundwate

Land subsidence associated with groundwater-level declines has been investigated by the U.S. Geological Survey in the Coachella Valley, California, since 1996. Groundwater has been a major source of agricultural, municipal, and domestic supply in the valley since the early 1920s. Pumping of groundwater resulted in water-level declines as much as 15 meters (50 feet) through the late 1940s. In 1949, the importation of Colorado River water to the southern Coachella Valley began, resulting in a reduction in groundwater pumping and a recovery of water levels during the 1950s through the 1970s. Since the late 1970s, demand for water in the valley has exceeded deliveries of imported surface water, resulting in increased pumping and associated groundwater-level declines and, consequently, an increase in the potential for land subsidence caused by aquifer-system compaction.

Land use and land cover influence on water quality in the last free-flowing river draining the western Sierra Nevada, California

Journal of Hydrology (Elsevier) | November 10th, 2005

Land use and land cover across 28 sub-basins within the Cosumnes Watershed, CA (1989 km2) were correlated to nitrate-N and total suspended solids (TSS) loading between w

Land use and land cover across 28 sub-basins within the Cosumnes Watershed, CA (1989 km2) were correlated to nitrate-N and total suspended solids (TSS) loading between water years 1999 and 2001. The impact of human development on stream water quality was evident as both agricultural area and population density predicted TSS loading in a linear mixed effects model. In contrast to the TSS model, the nitrate-N loading model was more complex with agriculture, grassland, and the presence or absence of waste water treatment plants (WWTPs) all contributing. The lack of correlation between population density and nitrate-N loading indicates that human habitation of the landscape does not impact stream nitrate levels until a WWTP is built within the sub-basin. During dry water years the models predict a linear reduction in TSS loading but the correlations to agriculture and population density remain positive. In contrast, nitrate is positively correlated to grasslands during average water years and negatively correlated during dry water years. Analysis of constituent fluxes from the upper watershed versus the lower watershed indicates that silica is derived primarily from the uplands and that during dry water years the upper watershed is an important source of dissolved organic carbon (DOC) and nitrate. The lower watershed contributes the majority of the sediment and nutrients during both dry and average water years, the one caveat being that during dry years the lower basin becomes a nitrate sink.

Land-use interactions, Oil-Field infrastructure, and natural processes control hydrocarbon and arsenic concentrations in groundwater, Poso Creek Oil Field, California, USA

Elsevier | May 7th, 2024

Latitudinal gradients of snow contamination in the Rocky Mountains associated with anthropogenic sources

Elsevier | March 26th, 2025

Seasonal snow is an important source of drinking water and recreation, and for agriculture in the Rocky Mountain region. Monitoring snow-water quality can inform on the e

Seasonal snow is an important source of drinking water and recreation, and for agriculture in the Rocky Mountain region. Monitoring snow-water quality can inform on the effects to the albedo and energy balance of the snowpack, and the sources of natural and anthropogenic aerosol and gases. This study analyzed metals in the seasonal snowpack from water year (WY) 2018 for 49 sites. Calcium, lanthanum, and cerium concentrations support the importance of mineral dust to the southern Rocky Mountains. Mercury (Hg), zinc (Zn), and cadmium (Cd) concentrations showed a similar spatial pattern to mineral dust, whereas antimony (Sb) concentrations were highest in the northern Rocky Mountains. To assess the relative contributions from dust versus anthropogenic contaminant sources, enrichment factors (EF) were calculated, with values above 10 indicating anthropogenic contamination. For Cd, Hg, Sb, and Zn, EF values exceeded 10 at northern sites. These observations were compared to spatial trends of EF values of Hg from WY2009 to WY2018, regional monitoring networks, and back trajectory analyses. The agreement between these datasets revealed temporally consistent contaminant sources and/or transport processes to the northern Rocky Mountains snowpack. Sources include current and historical mining and smelting in the region. Strategies to limit the emissions of these metals to the Northern Rockies could benefit from focusing on remediation of contaminated sites, and continued monitoring and mitigation of active mining and smelting.

Learning from California’s Experience with Small Water System Consolidations: A Workshop Synthesis

Center for Law, Energy, and the Environment (CLEE) | May 1st, 2018

California recognizes a human right to “safe, clean, affordable, and accessible water adequate for human consumption, cooking, and sanitary purposes.” However

California recognizes a human right to “safe, clean, affordable, and accessible water adequate for human consumption, cooking, and sanitary purposes.” However, California’s small and disadvantaged communities in both rural and urban contexts can find it especially challenging to fund the water system infrastructure, operations, monitoring, and maintenance necessary to achieve this goal.  Small water systems that provide water to at least 15 service connections and serve water to fewer than a thousand people are responsible for the bulk of the state’s drinking water quality violations, and an estimated 300 disadvantaged communities in California are served by systems that fail to meet state drinking water standards. Other Californians rely on very small water systems or private domestic wells that lack state requirements for water quality testing and may be especially unreliable.

Lithium in groundwater used for drinking-water supply in the United States

Science of the Total Environment (Elsevier) | May 1st, 2021

Lithium concentrations in untreated groundwater from 1464 public-supply wells and 1676 domestic-supply wells distributed across 33 principal aquifers in the United States

Lithium concentrations in untreated groundwater from 1464 public-supply wells and 1676 domestic-supply wells distributed across 33 principal aquifers in the United States were evaluated for spatial variations and possible explanatory factors. Concentrations nationwide ranged from <1 to 396 μg/L (median of 8.1) for public supply wells and <1 to 1700 μg/L (median of 6 μg/L) for domestic supply wells. For context, lithium concentrations were compared to a Health Based Screening Level (HBSL, 10 μg/L) and a drinking-water only threshold (60 μg/L). These thresholds were exceeded in 45% and 9% of samples from public-supply wells and in 37% and 6% from domestic-supply wells, respectively. However, exceedances and median concentrations ranged broadly across geographic regions and principal aquifers. Concentrations were highest in arid regions and older groundwater, particularly in unconsolidated clastic aquifers and sandstones, and lowest in carbonate-rock aquifers, consistent with differences in lithium abundance among major lithologies and rock weathering extent. The median concentration for public-supply wells in the unconsolidated clastic High Plains aquifer (central United States) was 24.6 μg/L; 24% of the wells exceeded the drinking-water only threshold and 86% exceeded the HBSL. Other unconsolidated clastic aquifers in the arid West had exceedance rates comparable to the High Plains aquifer, whereas no public supply wells in the Biscayne aquifer (southern Florida) exceeded either threshold, and the highest concentration in that aquifer was 2.6 μg/L. Multiple lines of evidence indicate natural sources for the lithium concentrations; however, anthropogenic sources may be important in the future because of the rapid increase of lithium battery use and subsequent disposal. Geochemical models demonstrate that extensive evaporation, mineral dissolution, cation exchange, and mixing with geothermal waters or brines may account for the observed lithium and associated constituent concentrations, with the latter two processes as major contributing factors.

Long-term variation in concentrations and mass loads in a semi-arid watershed influenced by historic mercury mining and urban pollutant sources

Science of the Total Environment (Elsevier) | December 15th, 2017

Urban watersheds are significantly anthropogenically-altered landscapes. Most previous studies cover relatively short periods, without addressing concentrations, loads, a

Urban watersheds are significantly anthropogenically-altered landscapes. Most previous studies cover relatively short periods, without addressing concentrations, loads, and yields in relation to annual climate fluctuations, and datasets on Ag, Se, PBDEs, and PCDD/Fs are rare. Intensive storm-focused sampling and continuous turbidity monitoring were employed to quantify pollution at two locations in the Guadalupe River (California, USA). At a downstream location, we determined loads of suspended sediment (SS) for 14 yrs., mercury (HgT), PCBs, and total organic carbon (TOC) (8 yrs), total methylmercury (MeHgT) (6 yrs), nutrients, and trace elements including Ag and Se (3 yrs), DDTs, chlordanes, dieldrin, and PBDEs (2 yrs), and PCDD/Fs (1 yr). At an upstream location, we determined loads of SS for 4 yrs. and HgT, MeHgT, PCBs and PCDD/Fs for 1 yr. These data were compared to previous studies, climatically adjusted, and used to critically assess the use of small datasets for estimating annual average conditions. Concentrations and yields in the Guadalupe River appear to be atypical for total phosphorus, DDTs, dieldrin, HgT, MeHgT, Cr, Ni, and possibly Se due to local conditions. Other pollutants appear to be similar to other urban systems. On average, wet season flow varied by 6.5-fold and flow-weighted mean (FWM) concentrations varied 4.4-fold, with an average 7.1-fold difference between minimum and maximum annual loads. Loads for an average runoff year for each pollutant were usually less than the best estimate of long-term average. The arithmetic average of multiple years of load data or a FWM concentration combined with mean annual flow was also usually below the best estimate of long-term average load. Mean annual loads using sampled years were also less than the best estimate of long-term average by a mean of 2.2-fold. Climatic adjustment techniques are needed for computing estimates of long-term average annual loads.

Los Angeles Sustainable Water Project: Ballona Creek Watershed

University of California, Los Angeles (UCLA) | November 1st, 2015

Implementing integrated water management systems (IWM) that incorporate all components of the urban water cycle, including imported water, local groundwater, captured st

Implementing integrated water management systems (IWM) that incorporate all components of the urban water cycle, including imported water, local groundwater, captured stormwater, greywater, and treated wastewater is crucial to creating a sustainable water supply for the city of Los Angeles (City). The City has researched, written, and initiated implementation of recommendations from many reports critical to creating an IWM plan for the City as well as to defining the current capacity of the system. While work on this issue has been ongoing for many years, the extreme drought currently impacting water supplies throughout California has created a new urgency to increase the City’s ability to provide a secure water supply through local sources. In April 2015, Governor Brown directed the first-ever statewide mandatory cut of 25% in urban water use due to the continuing drought conditions. In addition to statewide efforts, many policies and plans have been created on a local level within the City that address urban water management, integrated resources planning, stormwater capture, and groundwater management. The Los Angeles Mayor’s Office recently set strong goals to increase the sustainability of the City’s water supply over the next several years. The goals included completing a comprehensive sustainability plan containing objectives for water supply and demand in the City, which was released in April 2015 (Sustainable City pLAn). In an emergency drought directive released in October 2014, the Mayor identified additional accelerated water goals including reducing per capita potable water use by 20% by 2017 (from 2014 base-line of 130 gallons per capita per day (GPCD) to 104 GPCD), reducing the City’s reliance on MWD water by 50% by 2025, and converting 85% of public golf course acreage to recycled water by 2017. Through building upon regional research and reports that have been generated on potential components of the local water supply portfolio (e.g., groundwater, recycled water, and stormwater), as well as gathering and analyzing current data on flows of water and wastewater throughout the City systems and environment, this project further identifies and refines opportunities to implement integrated water management throughout the City. As water quality regulation in the Los Angeles area currently drives much of the current water management practices, we examined greater water self-reliance through this lens. Therefore, the City has been divided by watershed to assess Total Maximum Daily Load (TMDL) compliance alongside integrated water management opportunities and challenges that exist and must be addressed in order to meet water quality compliance requirements and maximize local water supply. This first report focuses on the Ballona Creek Watershed and the Hyperion Service Area; following reports will focus on the Dominguez Channel and Los Angeles River watersheds.