Base of fresh ground water (approximately 3,000 micromhos) in the San Joaquin Valley, California

U.S. Geological Survey (USGS) | June 30th, 1971

Widespread pumping of groundwater in the San Joaquin Valley began about 1900, and since 1940 pumpage has increased at an accelerated rate. In response to the heavy withdr

Widespread pumping of groundwater in the San Joaquin Valley began about 1900, and since 1940 pumpage has increased at an accelerated rate. In response to the heavy withdrawal of groundwater, water levels have declined rapidly beneath extensive areas of the valley. Consequently, it becomes necessary to delineate the base of fresh groundwater so that changes in thickness of the fresh-water zone can be monitored, and limited depths of water wells can be determined. In turn, those data will be useful in determining favorable areas for groundwater storage, and areas and depths for waste-water disposal wells. Because other agencies and the U.S. Geological Survey have collected a vast amount of well log and other data, most of the information in this report was assembled from existing files. However, for areas where data were scanty, a few hundred additional electrical logs were collected to supplement the available information.

Base of fresh water, groundwater salinity, and well distribution across California

National Academy of Sciences (NAS) | December 9th, 2020

The depth at which groundwaters transition from fresh to more saline—the “base of fresh water”—is frequently used to determine the stringency and types of measure

The depth at which groundwaters transition from fresh to more saline—the “base of fresh water”—is frequently used to determine the stringency and types of measures put in place to manage groundwater and protect it from contamination. Therefore, it is important to understand salinity distributions and compare defined bases of fresh water with salinity distributions and groundwater well depths. Here we analyze two distinct datasets: 1) a large set of total dissolved solids concentration (TDS) measurements (n = 216,754) and 2) groundwater well locations and depths (n = 399,454) across California. We find that 19 to 56% of the groundwater TDS measurements made at depths deeper than defined bases of fresh water pump fresh groundwater (TDS < 2,000 mg/L). Because fresh groundwater is found at depths deeper than the base of fresh water, current policies informed by base of fresh water assessments may not be managing and protecting large volumes of deep fresh groundwater. Furthermore, we find that nearly 4% of existing groundwater wells penetrate defined bases of fresh water, and nearly 16% of wells overlie it by no more than 100 m, evidencing widespread encroachment on the base of fresh water by groundwater users. Consequently, our analysis suggests that groundwater sustainability in California may be poorly safeguarded in some places and that the base-of-fresh-water concept needs to be reconsidered as a means to define and manage groundwater.

Basis of Design Report - Species Conservation Habitat

California Department of Water Resources (DWR) | April 14th, 2014

The Species Conservation Habitat (SCH) project provides shallow water habitat to support fish and wildlife dependent upon the Salton Sea that is being lost due to

The Species Conservation Habitat (SCH) project provides shallow water habitat to support fish and wildlife dependent upon the Salton Sea that is being lost due to salinity increases and the declining water surface elevation. The Project is located at the southern end of the Salton Sea (Sea) in Imperial County, California. Through the environmental review process, a Preferred Alternative was selected that encompasses 3,770 acres on both sides of the New River. The Project would include water supplies, berms to contain the water, and various other support facilities. The early start construction of the project is to develop habitat consistent with the EIS/EIR preferred alternative that is scaled down to fit the level of implementation funding currently available. The design described in this report is for early start project (Project) of the SCH and is limited to the 640 acres located within the bay on the east side of the New River. This report provides a summary of the primary design features and considerations associated with the habitat development. A more detailed discussion of the background, purpose, goals, design elements, Preferred Alternative, and Project impacts can be found in the 2011 draft EIS/EIR.  

Bay Area Green Infrastructure Water Quality Synthesis

San Francisco Estuary Institute (SFEI) | June 1st, 2018

San Francisco Bay is impacted by the numerous urban pollutants that flow from the surrounding landscape during storm events. In San Francisco Bay, total maximum daily lo

San Francisco Bay is impacted by the numerous urban pollutants that flow from the surrounding landscape during storm events. In San Francisco Bay, total maximum daily load (TMDL) clean-up plans are in place for polychlorinated biphenyls (PCBs) and mercury (Hg) (Davis et al., 2007; Davis et al., 2012). As municipalities strive to reach regulatory targets, green infrastructure (GI) presents a promising solution for managing stormwater pollutants while achieving additional environmental and social benefits. However, remaining data gaps including the best design layout, media composition, and vegetation and submerged zone effects on performance can prevent local managers from accurately assessing water quality benefits provided by green infrastructure as well as the maintenance needs to sustain adequate performance.

Beale Air Force Base Environmental Cleanup Program Issue 67

U.S. Air Force | October 31st, 2015

Benthic Invertebrate and Deposited Sediment TMDL Guidance for the Pajaro River Watershed

California State Water Resources Control Board (SWRCB) | March 1st, 2016

The Pajaro River and its tributaries are exposed to sediments from a variety of sources. To establish limits for regulating this pollutant, it is necessary to u

The Pajaro River and its tributaries are exposed to sediments from a variety of sources. To establish limits for regulating this pollutant, it is necessary to understand how and where deposition of sediments impact biological health. Benthic, or bottom-dwelling, invertebrates offer a direct way to assess the impacts of deposited sediment on the integrity of stream ecosystems. The channel bed is where sediments accumulate and persist, so benthic macroinvertebrates that live in this ha bitat provide a responsive indicator of the effect of these sediments. Previous criteria for bedded sediment fines in spawning gravels have been established for salmonids, but these may not be appropriate to all stream segments, are not typically measured in stream assessments, and are confounded by other factors limiting steelhead vitality. Instead, the effects of sediment cover can be evaluated using benthic macroinvertebrates (BMIs) as indicators of stream condition to assess any stream segment and can be related to the bioassessment and stream habitat surveys of the Surface Water Ambient Monitoring Program (SWAMP) . The approach taken in this study was to select 25 sites throughout the perennial Pajaro watershed and in the adjacent upper Coyote Creek watershed that represented a cross-section of land uses, above and below reservoirs (unregulated/regulated flows), and in varied geographic settings that would permit examining source area influences on sediment deposition. Rather than define conventional TMDL estimates for daily loads of sediment, a more relevant survey of the cover of deposited fine and sand (FS) sediments on the stream bed was used here to find the level at which BMIs lost integrity of species c omposition and diversity. BMI responses we re-examined at the reach scale (50-meter channel length ) and at local patch scales (30x3 0 cm) of varied FS sedim ent cover . The data were used to define target levels at which sediment impairs stream bed habitat quality. Reaches of varied sediment cover were compared to conditions at relatively undisturbed reference streams of the Central Coast region to evaluate sediment impacts. Significant loss of species diversity and altered community type occurred above a sediment cover range of 40% FS at both reach and local-patch scales. In a range of 20-40% FS , BMI diversity declined, showing incipient losses of biological integrity . Richness of mayfly, stonefly and caddisfly taxa richness (EPT) was used as an indicator of biological effects of sediment, and reduced diversity associated with sediment increase corresponded to declines below the criterion 10th percentile of reference site EPT found in other central coast streams . Because of multiple stressors, some streams may not achieve these sediment or EPT targets just by improving the local sediment condition . For example, streams that are regulated (below reservoirs) or in arid regions may be influenced by temperature, dissolved minerals and/or elevated pH , in addition to sediment . Rankings of streams surveyed were based either on sediment cover within the wetted stream width or the entire bankfull channel profile, accounting for both current habitat conditions and recent environmental exposure . Although the design of this study examined sediment deposition at different spatial scales and used a variety of sediment measures, the results are compatible with habitat and bioassessment surveys using standard SWAMP protocols. Only three to five of the 25 streams surveyed in the Pajaro region showed sediment and diversity levels indicating likely sediment deposition impacts. Results from this study can be used to identify streams where sediment degradation to biological integrity is likely (at >40% FS) , and those in a warning range (20-40% FS) that should be flagged for further assessment.

Bifenthrin, a ubiquitous contaminant, impairs the development and behavior of the threatened Longfin Smelt during early life stages

American Chemical Society (ACS) | June 23rd, 2023

The Longfin Smelt (Spirinchus thaleichthys) population in the San Franscisco Bay/Sacramento-San Joaquin Delta (Bay-Delta) has declined to ∼1% of its pre-1980s abundance

The Longfin Smelt (Spirinchus thaleichthys) population in the San Franscisco Bay/Sacramento-San Joaquin Delta (Bay-Delta) has declined to ∼1% of its pre-1980s abundance and, as a result, is listed as threatened under the California Endangered Species Act. The reasons for this decline are multiple and complex, including the impacts of contaminants. Because the spawning and rearing seasons of Longfin Smelt coincide with the rainy season, during which concentrations of contaminants increase due to runoff, we hypothesized that early life stages may be particularly affected by those contaminants. Bifenthrin, a pyrethroid insecticide commonly used in agricultural and urban sectors, is of concern. Concentrations measured in the Bay-Delta have been shown to disrupt the behavior, development, and endocrine system of other fish species. The objective of the present work was to assess the impact of bifenthrin on the early developmental stages of Longfin Smelt. For this, embryos were exposed to 2, 10, 100, and 500 ng/L bifenthrin from fertilization to hatch, and larvae were exposed to 2, 10, and 100 ng/L bifenthrin from one day before to 3 days post-hatch. We assessed effects on size at hatch, yolk sac volume, locomotory behavior, and upper thermal susceptibility (via cardiac endpoints). Exposure to these environmentally relevant concentrations of bifenthrin did not significantly affect the cardiac function of larval Longfin Smelt; however, exposures altered their behavior and resulted in smaller hatchlings with reduced yolk sac volumes. This study shows that bifenthrin affects the fitness-determinant traits of Longfin Smelt early life stages and could contribute to the observed population decline.

Bioanalytical and chemical-specific screening of contaminants of concern in three California (USA) watersheds

Heliyon (Elsevier) | May 5th, 2022

To broaden the scope of contaminants monitored in human-impacted riverine systems, water, sediment, and treated wastewater effluent were analyzed using receptor-based cel

To broaden the scope of contaminants monitored in human-impacted riverine systems, water, sediment, and treated wastewater effluent were analyzed using receptor-based cell assays that provide an integrated response to chemicals based on their mode of biological activity. Samples were collected from three California (USA) watersheds with varying degrees of urbanization and discharge from municipal wastewater treatment plants (WWTPs). To complement cell assay results, samples were also analyzed for a suite of contaminants of emerging concern (CECs) using gas and liquid chromatography-mass spectrometry (GC- and LC-MS/MS). For most water and sediment samples, bioassay equivalent concentrations for estrogen and glucocorticoid receptor assays (ER- and GR-BEQs, respectively) were near or below reporting limits. Measured CEC concentrations compared to monitoring trigger values established by a science advisory panel indicated minimal to moderate concern in water but suggested that select pesticides (pyrethroids and fipronil) had accumulated to levels of greater concern in river sediments. Integrating robust, standardized bioanalytical tools such as the ER and GR assays utilized in this study into existing chemical-specific monitoring and assessment efforts will enhance future CEC monitoring efforts in impacted riverine systems and coastal watersheds.

Biological opinion on the coordinated operations of the Central Valley Project (CVP) and State Water Project (SWP)

U.S. Fish and Wildlife Service (FWS) | December 15th, 2008

On May 16, 2008, the U.S. Bureau of Reclamation and the California Department of Water Resources asked the Service to initiate consultation on the Long-Term Operational C

On May 16, 2008, the U.S. Bureau of Reclamation and the California Department of Water Resources asked the Service to initiate consultation on the Long-Term Operational Criteria and Plan (OCAP) for coordination of the Central Valley Project and State Water Project, specifically concerning the delta smelt and its critical habitat. (See OCAP Legal Archives.) On December 15, 2008, the Fish & Wildlife Service issued a biological opinion (BO) on the Long-Term Operational Criteria and Plan (OCAP) for coordination of the Central Valley Project and State Water Project. The Service determined that the continued operation of these two water projects, as described in the plan, was likely to jeopardize the continued existence of the delta smelt and adversely modify its critical habitat. The inclusion by the Service of reasonable and prudent alternatives, and their acceptance by the water agencies, avoided jeopardy and adverse modification.

Biological sensitivities to high-resolution climate change projections in the California current marine ecosystem

Wiley | July 28th, 2022