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A Field Guide to the Identification of the Ordinary High Water Mark (OHWM) in the Arid West Region of the Western United States: A Delineation Manual

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A Field Guide to the Identification of the Ordinary High Water Mark (OHWM) in the Arid West Region of the Western United States: A Delineation Manual
U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory | August 1, 2008...
Summary
The Ordinary High Water Mark (OHWM) is an approach for identifying the lateral limits of non-wetland waters. However, determining whether any non-wetland water...

The Ordinary High Water Mark (OHWM) is an approach for identifying the lateral limits of non-wetland waters. However, determining whether any non-wetland water is a jurisdictional “Water of the United States” (WoUS) involves further assessment in accordance with the regulations, case law, and clarifying guidance. In the Arid West region of the U.S., the most problematic Ordinary High Water (OHW) delineations are associated with the ephemeral/intermittent channel forms that dominate the Arid West landscape. This report presents a method for delineating the lateral extent of the non-wetland waters in the Arid West using stream geomorphology and vegetation response to the dominant stream discharge.

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A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA
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A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA
Science of the Total Environment | June 9, 2017...
Summary
Intense demand forwater in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater resource....
Intense demand forwater in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater resource. To assess contamination risk in the region, we developed a hybrid, non-linear, machine learning model within a statistical learning framework to predict nitrate contamination of groundwater to depths of approximately 500m below ground surface.

A database of 145 predictor variables representing well characteristics, historical and current field and landscape-scale nitrogen mass balances, historical and current land use, oxidation/reduction conditions, groundwater flow, climate, soil characteristics, depth to groundwater, and groundwater age were assigned to over 6000 private supply and public supply wells measured previously for nitrate and located throughout the study area. The boosted regression tree (BRT) method was used to screen and rank variables to predict nitrate concentration at the depths of domestic and public well supplies.

The novel approach included as predictor variables outputs from existing physically based models of the Central Valley. The top five most important predictor variables included two oxidation/reduction variables (probability of manganese concentration to exceed 50 ppb and probability of dissolved oxygen concentration to be below 0.5 ppm), field-scale adjusted unsaturated zone nitrogen input for the 1975 time period, average difference between precipitation and evapotranspiration during the years 1971–2000, and 1992 total landscape nitrogen input.

Twenty-five variables were selected for the final model for log-transformed nitrate. In general, increasing probability of anoxic conditions and increasing precipitation relative to potential evapotranspiration had a corresponding decrease in nitrate concentration predictions.

Conversely, increasing 1975 unsaturated zone nitrogen leaching flux and 1992 total landscape nitrogen input had an increasing relative impact on nitrate predictions.

Three-dimensional visualization indicates that nitrate predictions depend on the probability of anoxic conditions and other factors, and that nitrate predictions generally decreased with increasing groundwater age.

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A Water Resources Data-Network Evaluation for Monterey County, California, Phase 3: Northern Salinas River Drainage Basin
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A Water Resources Data-Network Evaluation for Monterey County, California, Phase 3: Northern Salinas River Drainage Basin
U.S. Geological Survey, Monterey County Flood Control and Water Conservation District | December 15, 1990...
Summary
This report presents an evaluation of water resources data collection networks in the northern Salinas River drainage basin, Monterey County, California. The evaluation,...

This report presents an evaluation of water resources data collection networks in the northern Salinas River drainage basin, Monterey County, California. The evaluation, done in cooperation with the Monterey County Flood Control and Water Conservation District, covers both quantity and quality monitoring by precipitation, surface-water, and ground-water networks. The report describes existing networks in the study area and possible additional data collection.

The study identified 34 precipitation gages in the study area, of which 20 are active. The stations are concentrated in the northwestern part of the study area. Data are lacking for the eastern and southern parts of the study area, as well as the southwestern slopes of the Gabilan Range. No precipitation-quality networks were identified. Possible data-collection efforts for precipitation quality include monitoring for acid rain and for pesticides in precipitation.

The study identified 10 streamflow-gaging stations, of which 6 are active. To meet the objectives for streamflow networks that are outlined in the report, all sites could be reactivated, and two of the inactive sites could be relocated to improve the reliability of the data. Besides these stations, nine possible additional streamflow-gaging sites were identified.

The Monterey County Flood Control and Water Conservation District samples one surface-water site for suspended sediment, specific conductance, and chlorides. Several agencies have done water-quality sampling in the past, but only five sites are active. Reactivation of the 45 inactive sites might help to meet the various surface-water-quality objectives described in the report. Development of a stream-reach rating system also could help to identify parts of the study area most in need of sampling.

The Monterey County Flood Control and Water Conservation District maintains three networks to measure ground-water levels on a monthly basis, during peak irrigation, and at the end of the irrigation season. The District measures water levels in 318 wells. The only other network identified for this report was operated by the U.S. Geological Survey, and none of its five wells are active. The study identified 128 sections in which no ground-water-level monitoring is presently done. Well coverage is densest in the saltwater-intrusion areas near Castroville, California. Wells in the rest of the study area are more sparsely distributed and are concentrated down the center of the drainage basin in the alluvial ground-water basin.

The ideal initial baseline network of ground-water-quality wells would be an evenly spaced grid of index wells within each aquifer, with a density of one per section. Once baseline conditions were established, representative wells could be selected and monitored annually. As of 1985, the Monterey County Flood Control and Water Conservation District monitored 379 study wells in the area for various water-quality conditions. Other networks monitor (or propose the monitoring of) 135 wells. The District collects samples in summer months to monitor saltwater intrusion near Castroville.

Annual samples also are analyzed for chloride, specific conductance, and nitrate. Every 5 years, the District does a complete mineral analysis on each study well. Improvements in network coverage are suggested to better approximate ideal network coverage. The adequacy of wells in existing monitoring networks for representing actual conditions in the ground-water basins was not established conclusively.

Possible redundancy of information from existing networks was not evaluated statistically. Despite these limitations, this report does provide a basis for assessing the adequacy of ground-water-level networks in the study area. The computerized Geographic Information System (GIS) that is planned for Monterey County could easily use the information in this report for the needed initial analysis of network adequacy. The feasibility of management and analysis of large complicated data bases (such as the ground water networks identified in this report) is substantially improved through the use of state-of-the-art GIS tools now available.

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Adapting to Change: Utility Systems and Declining Flows

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Adapting to Change: Utility Systems and Declining Flows
California Water Urban Agencies | November 1, 2017...
Summary
During the recent historic drought, Californians responded to the call for emergency statewide water use reductions, which the state has recognized as a...

During the recent historic drought, Californians responded to the call for emergency statewide water use reductions, which the state has recognized as a highly successful outcome. However, this significant reduction in water demands has brought to light some unintended consequences of declining flows that ripple throughout the interconnected urban water cycle. These observations offer a preview into the potential impact of establishing permanent indoor water use targets at or below the thresholds achieved as a result of the governor’s emergency conservation mandate.

California’s water industry leaders, including regulators and purveyors, are working to understand the system-wide impacts of increased conservation so that decision makers are better informed as they address California’s current and future water challenges.

Through a partnership with California Association of Sanitation Agencies (CASA), Water Research Foundation(WRF), WateReuse California, and California Water Environment Association(CWEA), California WaterUrban Agencies(CUWA) has developed this white paper to provide decisionmakers, water/wastewater system managers, and other stakeholders an understanding of the impacts of declining flows resulting from substantial reductions in indoor water use and how utilities are adapting to these circumstances.

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Advancement of Salinity and Flow Monitoring in the San Francisco Bay Delta, San Francisco Bay Delta Action Plan Implementation Support, FINAL REPORT

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Advancement of Salinity and Flow Monitoring in the San Francisco Bay Delta, San Francisco Bay Delta Action Plan Implementation Support, FINAL REPORT
U.S. Geological Survey, U.S. Environmental Protection Agency | February 1, 2017...
Summary
This report evaluates the cost and utility of adding coupled surface and near-bottom salinity monitors along the axis of the San Francisco Estuary,...

This report evaluates the cost and utility of adding coupled surface and near-bottom salinity monitors along the axis of the San Francisco Estuary, and the types of equipment and approximate costs of this additional monitoring effort. Expanding the monitoring network by adding downstream monitoring stations, adding stations at depth, and increasing the resolution of monitoring stations along the axis of the estuary will generate data that capture tidal dynamics and may be used to derive equations that predict salinity and other hydrodynamic endpoints with greater precision than currently possible. The proposed monitoring is expected to enhance the hydrodynamic modeling of the salt field and the accuracy of compliance and prediction methods in the estuary.

Springtime outflows through the San Francisco Estuary are managed through the position of the 2 parts per thousand bottom salinity isohaline (X2) along the center-line of the estuary, measured in kilometers relative to the Golden Gate Bridge. X2 is calculated from surface salinity measurements with a constant vertical conversion factor. The current framework of sampling stations does not collect near-bottom salinity along the estuary center-line, does not extend far enough down-estuary to adequately characterize X2 during high flows, and the separation of monitoring locations limits the precision with which the position of X2 can be calculated.

Near-surface and near-bed salinity and turbidity sensors and ancillary hardware could be added to the estuary for an estimated cost of ~ $780K in capital costs and $500K/yr in operation, maintenance, and data processing costs based on a proposed addition to an existing surface salinity network in San Francisco Estuary operated by the US Geological Survey. While this document does not recommend a particular plan for implementation, the compiled information provides rough costs for planning considerations. Data collected through a network of this kind could improve precision of compliance methods with the existing Delta outflow standard. With data collected over time, it would support modifications to a new/modified Delta outflow standard, improve our ability to assess the effectiveness of water quality standards, and improve protection of water supply and aquatic life habitat. These data would also improve the salinity modeling capability and accuracy for future predictions and past evaluations. Expanding the monitoring network also provides a platform to connect hydrodynamic and biological measurements which is necessary for integrating biological and hydrodynamic modeling and advancing knowledge of estuarine mechanisms that influence fish population trends. The specific design of a monitoring network and whether or not the improvements can be optimized for their potential outputs was beyond the scope of the present document and needs to be based on a broader discussion among science experts, regulators, and the regulated community.

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An Index of Biotic Integrity (IBI) for Perennial Streams in California’s Central Valley

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An Index of Biotic Integrity (IBI) for Perennial Streams in California’s Central Valley
California State Water Resources Control Board | December 1, 2008...
Summary
Bioassessment is the science of using aquatic organisms as indicators of ecological condition in streams in rivers. Many types of organisms can be...

Bioassessment is the science of using aquatic organisms as indicators of ecological condition in streams in rivers. Many types of organisms can be used as indicators, for example fish or algae, but bioassessment is most frequently based on benthic macroinvertebrates (BMIs), which are small but visible bottom-dwelling organisms such as insects. BMI data sets typically consist of long lists of species (or taxa) found in a sample and their relative abundances. These data can be simplified into measures of biological condition such as indices of biotic integrity (IBIs) that are designed to be sensitive to human-caused alterations to the landscape, to stream channels and riparian zones, and to water chemistry. IBIs function much like economic indicators: high IBI scores reflect good ecological conditions while low IBI scores reflect poor ecological conditions.

Bioassessment is increasingly used throughout California by water quality monitoring programs, but in the Central Valley bioassessment is more challenging than in other regions of the state because the entire landscape and most streams are highly altered by human activities such as urbanization, agriculture and water diversions. This makes it impossible to evaluate how BMIs respond across a complete gradient of human disturbance within the region, that is, from minimally disturbed reference sites where human activity is absent or minimal and which therefore set the benchmark for biological expectations, to the most altered sites with degraded biology. In the Central Valley, minimally disturbed reference sites are no longer available. Even the ‘least-disturbed’ sites, which represent the best-available chemical, physical and biological habitat conditions given the current state of the landscape, are markedly disturbed. Reference sites in other parts of California, such as the Sierra Nevada or the Sierra foothills, may be significantly less disturbed than Central Valley reference sites.

In this study, BMI data sets from 11 studies conducted at various intervals over the last 14 years were compiled to build an IBI for Central Valley streams. Data were not collected consistently by the different studies, and many gaps were present in associated physical habitat and water chemistry data sets. This could be corrected for BMI samples by standardizing to a consistent level of taxonomic effort. Gaps in other data could not be addressed. Criteria for defining ‘best-available’ reference sites were established as data allowed and were based on local urban and agricultural intensity, stream channel and riparian condition, and stream substrate composition. Eighty BMI metrics were evaluated for inclusion in the IBI based on 4 criteria: 1) sufficient range for scoring; 2) responsiveness to land use and/or local disturbance variables measured at the 150-meter sampling reach (as data allowed); 3) good discrimination between reference and test sites; 4) lack of correlation with other responsive metrics. Five final metrics were selected and scored for inclusion in the IBI: collector richness (number of taxa that are collector- feeders), predator richness (number of taxa that are predators), percent EPT taxa (percent of taxa that are mayflies, stoneflies, or caddisflies), percent clinger taxa (percent of taxa that cling to vegetation) and Shannon diversity (a composite measure of taxonomic richness and evenness of abundance). The final IBI showed good discrimination between reference and test sites, and was validated with an independent data set. BMI metrics and the final IBI were more strongly related to reach-scale physical habitat variables than to water chemistry or land use variables, but detailed water chemistry was lacking for many sites, and some studies have shown that response to land use diminishes when more than 10% of a watershed is degraded by human activities.

Despite data gaps that were less than ideal for indicator development, this study is the first to set expectations for Central Valley BMI assemblages based on best-available reference sites. The Central Valley IBI can be used as a general interpretive framework for benthic samples collected from perennial streams on the valley floor and provides an objective means for rating biological condition in a region with high urban and agricultural intensity. The ability to rank sampling sites relative to explicitly defined biological expectations is essential to any biological monitoring program. Therefore, this index may prove useful in several monitoring applications, including California’s non- point source CMAP program where sampling was stratified to assess and compare stream condition in urban, agricultural and forested watersheds, in stormwater monitoring programs, in point-source pollution investigations, and in stream restoration monitoring. Key recommendations include: 1) that all future bioassessment projects in the Central Valley should collect quantitative physical habitat and water chemistry with consistent protocols at all sites; in situ chemistry and rapid (qualitative) physical habitat are not sufficient for screening reference sites or evaluating BMI responses to stressor gradients; 2) that bioassessment should be added to NPS monitoring where programs are already collecting more intensive stressor data such as pesticides, nutrients and metals. This will provide California’s monitoring programs with better datasets to support future analyses.

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

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Benthic Invertebrate and Deposited Sediment TMDL Guidance for the Pajaro River Watershed
California State Water Resources Control Board | March 1, 2016...
Summary
The Pajaro River and its tributaries are exposed to sediments from a variety of sources. To establish limits for regulating this pollutant, it...

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.

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Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life

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Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life
California State Water Resources Control Board, San Francisco Estuary Institute | October 24, 2007...
Summary
This report was written for the State Water Resources Control Board’s Surface Water Ambient Monitoring Program (SWAMP) as a step toward the development...

This report was written for the State Water Resources Control Board’s Surface Water Ambient Monitoring Program (SWAMP) as a step toward the development of an improved bioaccumulation monitoring program for California. The report provides a review of bioaccumulation monitoring data generated under three historic State Board programs (the Toxic Substances Monitoring Program, the State Mussel Watch Program, and the Coastal Fish Contamination Program) and other major bioaccumulation studies since 1970. Future monitoring will be guided by assessment questions developed for the SWAMP. The objective of this report was to evaluate how well the historic data from the State Board programs and from other major monitoring efforts since 1970 address these questions. This exercise has provided a substantial amount of information about present and historical impacts of pollutant bioaccumulation on shing and aquatic life in California, and has also highlighted areas where improved sampling approaches can better address the assessment questions.

Present concentrations of pollutants in many California water bodies are high enough to cause concern for possible effects on human health and to have a significant impact on the fishing beneficial use. Consumption advisories, 303(d) listings, and the bioaccumulation database as a whole provide three indices of the status of this impact. Consumption advisories exist for an increasing number of water bodies, but these represent only a fraction of the areas likely to need them. Lack of suitable data is a major impediment to developing advice for additional water bodies. A US E.P.A. evaluation of the 2002 303(d) List indicated that large portions of the state had not been assessed, especially rivers and coastline. Most of the lake area in the state (61%) had been assessed, and a relatively small percentage of the total area (6%) was classified as impaired. Assessment of lakes, however, has focused primarily on the largest lakes, leaving the vast majority of smaller lakes unsampled. Many of these small lakes are near population centers and are popular for shing. Bays and estuaries had been thoroughly assessed (98% of the area) and 93% of the total area was impaired.

Evaluation of the most recent monitoring data (collected from 1998-2003) indicates that, for the locations sampled, 32% had low concentrations of pollutants, 42% had moderate concentrations, 18% had high concentrations, and 8% had very high concentrations (Figure 1). Concentrations in the low category are in a range where consumption is generally encouraged by the California Office of Environmental Health Hazard Assessment (OEHHA) (Klasing and Brodberg 2006). OEHHA is the agency responsible for managing health risks due to contaminated sport fish in California. Concentrations in the very high category are in a range where OEHHA discourages consumption (Klasing and Brodberg 2006). Lakes assigned to the moderate, high, or very high concentration categories were primarily affected by mercury, with PCBs also playing a lesser role.

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Biological Condition of Non-Perennial Streams and Spring-Fed Oases in the Colorado River Basin Region
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Biological Condition of Non-Perennial Streams and Spring-Fed Oases in the Colorado River Basin Region
State Water Resources Control Board | August 22, 2014...
Summary
The Colorado River Basin Regional Water Board conducted bioassessment sampling at high-quality (i.e., “reference”) streams in their region during 2013-2015. The purpose of...
The Colorado River Basin Regional Water Board conducted bioassessment sampling at high-quality (i.e., “reference”) streams in their region during 2013-2015. The purpose of the study was to characterize the biological condition of these streams, which had never been done before, and to expand ongoing research as to whether existing biological indices, developed primarily for perennial streams, apply in nonperennial streams. The latter are usually excluded from bioassessment surveys, but make up the majority of stream length in the most arid parts of the state like the Colorado River Basin, leaving stream condition assessments in such regions largely incomplete. The indices evaluated were the California Stream Condition Index (CSCI) based on benthic macroinvertebrates and the first to have statewide applicability in perennial streams, and the D18 and S2 indices for diatoms and soft algae, respectively, developed for use in perennial streams of southern coastal California. Sixteen sites were sampled during the 3-year period, and data loggers that measure water depth were deployed for 2 of the 3 years to characterize the hydrologic regime at each site. Most sites were nonperennial, but a few were spring-fed perennial oases. Fourteen of the sites passed formal reference screening criteria developed by statewide programs.

The CSCI and S2 indices had generally good applicability in the region, with most samples from reference sites indicated either good or fair (i.e., non-degraded) biological condition. The mean CSCI score at regional reference sites was slightly lower than the statewide mean (i.e., 0.90 vs. 1.0, respectively), but the difference could be an artifact of a relatively small regional data set. The fact that CSCI and S2 performed as well as they did in a region, and in a set of stream types, largely excluded from their development indicates that the indices can be used in nonperennial streams (and spring-fed oases) in the Colorado River Basin as long as certain minimum flow conditions are met, such as sustained flow for several weeks prior to sampling and sufficient wetted width to employ existing protocols developed for perennial streams. By contrast, the D18 index did not perform well in the region. A majority of samples from reference sites indicated poor or very poor biological condition when condition thresholds based on statewide data sets were used, but even when more relaxed thresholds based on just south coast reference sites were applied, the number of reference sites in good or fair condition was still much lower than expected. This was not a result of regional reference sites being of low quality, but was most likely an artifact of applying the index to a set a stream types unintended for its use. Development of statewide algal indices is underway, which may improve the performance of diatom indices in the southern desert.

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Biology-based Stressor Thresholds

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Biology-based Stressor Thresholds
California State Water Resources Control Board, Non-point Source Program | October 1, 2011...
Summary
The objective of this memo is to describe how biological assessment data (such as those collected using Surface Water Ambient Monitoring Program (SWAMP)...

The objective of this memo is to describe how biological assessment data (such as those collected using Surface Water Ambient Monitoring Program (SWAMP) bioassessment protocols) can be used to develop biologically-relevant stressor thresholds. This memo describes an objective approach for setting regulatory stressor thresholds based on the association between biological condition and stressor intensity gradients. While these relationships show a large amount of variability typical of biological data, there are clear thresholds that indicate levels below or above which stream health is maintained or degraded.

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Bulletin No. 52-B Salinas Basin Investigation Summary Report
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Bulletin No. 52-B Salinas Basin Investigation Summary Report
California Department of Water Resources, formerly State Department of Public Works Division of Water Resources | December 13, 1946...
Summary
The Board of Supervisors and the Flood Control and Water Conservation Conmittee of the County of Monterey became concerned in April 1944 over...
The Board of Supervisors and the Flood Control and Water Conservation Conmittee of the County of Monterey became concerned in April 1944 over the intrusion of saline water in the ground water supply utilized for irrigation, domestic and industrial purposes in the lower reaches of the Salinas Basin near Monterey Bay. The entire agricultural and urban development in the basin depends on an adequate supply of ground water of good quality.

There had been some abandonment of wells in the Salinas Basin near the bay shore due to excessive salinity as early as 1938. Accelerated encroachment of the contamination occurred in 1943, and the matter was brought to public attention in 1944. The County of Monterey and the Department of Public Works, State of California, executed a contract on July 10, 1944, providing for maintenance in cooperation an investigation of the water resources of the Salinas Valley in Monterey County and conditions relative thereto which obtain in the valley or affect the water supplies available therefor. It further provides that the Department shall prepare a report based on the investigation setting forth the physical facts pertinent to water supply and to salt water Intrusion, and if possible, incorporate findings as to a method or methods of solving the problems involved.

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Characterizing Nitrates in Central Coast Groundwater

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Characterizing Nitrates in Central Coast Groundwater
Central Coast Groundwater Coalition (CCGC) | April 1, 2016...
Summary
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...

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.

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Comparison of the Performance of Different Bioassessment Methods: Similar Evaluations of Biotic Integrity from Separate Programs and Procedures

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Comparison of the Performance of Different Bioassessment Methods: Similar Evaluations of Biotic Integrity from Separate Programs and Procedures
Journal of the North American Benthological Society | January 16, 2006...
Summary
Regional bioassessment programs of states, various federal agencies, and other governmental and private groups often use different methods to collect and analyze stream...

Regional bioassessment programs of states, various federal agencies, and other governmental and private groups often use different methods to collect and analyze stream invertebrate samples. This lack of uniformity has created concern and confusion over the comparability of disparate sources of data, but few studies have attempted to evaluate differences in performance between methods or to reconcile the results produced from different methods. We conducted concurrent sampling at 40 sites in the eastern Sierra Nevada of California using 3 bioassessment methods to obtain directly comparable data sets. The riffle-based methods (University of California Sierra Nevada Aquatic Research Laboratory [UC-SNARL, Lahontan Water Board], California Stream Bioassessment Protocol, and US Forest Service Region 5) differed at each stage from field sample collection to laboratory processing and data analysis. We used a performance-based methods system to compare precision, uniformity, discrimination, accuracy, and correlations among multimetric Index of Biotic Integrity (IBI) scores and multivariate River Invertebrate Prediction and Classification System (RIVPACS)-type observed/expected (O/E) ratios. Reference and test sites were identified using local and upstream-watershed disturbance criteria, and invertebrate community measures and models were then developed to discriminate between reference and test sites. The more- intensive UC-SNARL method showed slightly, but consistently, greater sensitivity for discriminating impairment than the other 2 methods. The UC-SNARL method produced greater differences between reference- and test-site means relative to lower reference-site standard deviations than the other 2 methods. However, assessment scores were highly correlated among methods and distinguished reference from test sites with similar accuracy among methods despite the slight differences in performance.

Our results show that differing bioassessment methods can yield very similar, effective discrimination of impaired biological condition even though they have multiple differences in field and laboratory protocols (mesh size, replication, area sampled, taxonomic resolution, total counts). Moreover, this conclusion did not depend on the approach taken to data analysis because both multimetric IBIs and multivariate RIVPACS-type O/Es were in close agreement. Methodological uniformity is important when coordinating monitoring programs, but our results suggest that data from multiple sources could potentially be used interchangeably and for cross-validation of assessments of stream biological integrity.

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Comparisons of Targeted-riffle and Reach-wide Benthic Macroinvertebrate Samples: Implications for Data Sharing in Stream-condition Assessments

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Comparisons of Targeted-riffle and Reach-wide Benthic Macroinvertebrate Samples: Implications for Data Sharing in Stream-condition Assessments
Journal of the North American Benthological Society | January 1, 2007...
Summary
Recent comparisons of benthic macroinvertebrate (BMI) sampling protocols have shown that samples collected from different habitat types generally produce consistent stream classifications and...

Recent comparisons of benthic macroinvertebrate (BMI) sampling protocols have shown that samples collected from different habitat types generally produce consistent stream classifications and assessments. However, these comparisons usually have not included biological endpoints used by monitoring agencies, such as multimetric indices (e.g., benthic index of biotic integrity [B-IBI]) or observed- to-expected (O/E) indices of taxonomic completeness, as target variables, and estimates of method precision are rarely provided. Targeted-riffle (TR) and reach-wide (RW) benthic samples have been collected at thousands of sites across the western USA, but little guidance is available for understanding 1) the extent to which raw data sets can be combined in regional or large-scale analyses, 2) the degree of precision afforded by each method, or 3) the efficacy of cross-application of biological indicators derived from one sample type to the other. To address these issues, we used data from 193 sites in California where the Environmental Monitoring and Assessment Program (EMAP) collected the 2 samples side by side. We also conducted a separate study wherein 3 replicates of each sample type were collected from 15 streams to estimate minimum detectable difference (MDD) as a measure of each method’s precision. Metrics calculated from TR and RW samples showed similar dose–response relationships to stressors gradients and similar raw scoring ranges. Biological indices (B-IBI, O/E0, and O/E50) derived from RW samples were more precise than those derived from TR samples, but precision differences were not substantial. On average, pairwise differences in any index between TR and RW sample types were much less than the MDD associated with either sampling method. We observed a weak but consistent bias toward higher O/E50 scores from TR samples than from RW samples at the highest elevations and in the largest watersheds. Broad-scale condition assessments were nearly identical when B-IBI and O/E0 were used as endpoints, and assessments based on O/E50 were only slightly less similar. Our analyses indicate that raw data sets and biological indicators derived from TR and RW samples may be generally interchangeable when used in ambient biomonitoring programs.

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Condition of California Perennial, Wadeable Streams Based on Algal Indicators

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Condition of California Perennial, Wadeable Streams Based on Algal Indicators
Southern California Coastal Water Research Project, San Diego Regional Water Quality Control Board | October 1, 2013...
Summary
Algae can serve as indicators of stream ecological condition in two ways. Information about algal community composition can be used for bioassessment analogous...
Algae can serve as indicators of stream ecological condition in two ways.

Information about algal community composition can be used for bioassessment analogous to the way in which benthic macroinvertebrates (BMIs) are employed (e.g., as described in Ode et al. 2011). When algae occur in excess (i.e., in the case of eutrophication), stress to the system can result; as such, the total amount of algae present also becomes an indicator of stream health in its own right.

To date, the state of California has invested in several initiatives to build capacity for conducting stream algal assessment. This includes support for creation of a planning document funded by State Water Resources Control Board’s (SWRCB) Surface Water Ambient Monitoring Program (SWAMP) (Fetscher and McLaughlin 2008) and establishment of SWAMP Standard Operating Procedures (SOPs) for field sample collection (Fetscher et al. 2009) and a laboratory processing and enumeration SOP (currently in review) for determining algal community composition. In addition, an algae Index of Biotic Integrity (IBI) for bioassessment of southern California streams was recently completedby Fetscher et al. (2013), and a state algae laboratory, based at California State University San Marcos, has been established.

Over the past several years, the state of California’s Perennial Stream Assessment (PSA)and Reference Condition Management Program (RCMP), the southern California Stormwater Monitoring Coalition (SMC), and other smaller programs have collected and processed algae samples using the SWAMP protocols. As such, a substantial amount of standardized data on stream algae and instream, vascular macrophytes (together hereafter referred to as stream “primary producer indicators”) have been collected in California since 2007. However, no consolidated analysis of these data has been conducted so far. This report represents such an effort.

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Detections of current-use pesticides at 12 surface water sites in California during a 2-year period beginning in 2015

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Detections of current-use pesticides at 12 surface water sites in California during a 2-year period beginning in 2015
U.S. Geological Survey (USGS), Central Valley Regional Water Quality Control Board | July 27, 2018...
Summary
Surface water samples were collected by the U.S. Geological Survey and multiple cooperators during base flow/irrigation runoff and storm runoff conditions from 12...
Surface water samples were collected by the U.S. Geological Survey and multiple cooperators during base flow/irrigation runoff and storm runoff conditions from 12 sites throughout California, over 2 consecutive years beginning in April 2015, from both urban and agriculturally dominated watersheds. Water samples were analyzed by gas chromatography/mass spectrometry and liquid chromatrography/tandem mass spectrometry for a suite of 157 pesticides and degradates. Suspended sediments associated with these water samples were analyzed by gas chromatography/mass spectrometry for a suite of 131 pesticides and degradates. Overall, 85 pesticides and degradates were detected in the water: 32 fungicides, 25 herbicides, 27 insecticides, and 1 synergist. In the suspended sediment, 29 pesticides were detected: 9 fungicides, 10 herbicides, and 10 insecticides. Sixteen pesticides (bifenthrin, carbendazim, chlorpyrifos, clothianidin, diazinon, diuron, fenpyroximate, fipronil, fipronil sulfone, fluopicolide, imidacloprid, metolachlor, novaluron, oxyflurofen, permethrin, and simazine) were detected in the water at concentrations that were above at least one aquatic life benchmark value as defined by the U.S Environmental Protection Agency.

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DRERIP Ecosystem Conceptual Model: Chemical stressors
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DRERIP Ecosystem Conceptual Model: Chemical stressors
California Department of Fish and Wildlife | February 5, 2008...
Summary
The Sacramento-San Joaquin Delta ecosystem comprises many different habitat types, and is home to a large number of species. Thousands of chemical contaminants...
The Sacramento-San Joaquin Delta ecosystem comprises many different habitat types, and is home to a large number of species. Thousands of chemical contaminants have been or are being introduced into the Delta. The conceptual model presented here is therefore general in nature, and is intended to provide a framework for more refined models for individual species, habitats and, in particular, contaminants of interest, for example selenium, mercury and pyrethroids.

The model consists of three major submodels (Figure 1). Submodel 1: Exposure assessment which includes fate and transport of contaminants and the co-occurrence of chemicals with Delta organisms; the intermediate outcome of this submodel is “Exposure Concentration”. Submodel 2: Bioavailability of contaminants to Delta organisms; the intermediate outcome of this submodel is “Bioavailable Concentration” or “Dose”. Submodel 3: Toxic effects assessment with the final model outcome “Population Level Effects”.

In the following narrative, we provide a description for each submodel, its parameters, and linkages to other models. We discuss the model’s limitations and provide recommendations for its application in management.

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Effects of wildfire on benthic macroinvertebrate assemblages in Southern California streams and implications for bioassessment monitoring programs
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Effects of wildfire on benthic macroinvertebrate assemblages in Southern California streams and implications for bioassessment monitoring programs
California State Water Resources Control Board | June 13, 2012...
Summary
Wildfires are common in arid regions of southern California, sometimes burning as much as half a million acres in a season. These fires...
Wildfires are common in arid regions of southern California, sometimes burning as much as half a million acres in a season. These fires often cause dramatic impacts to the vegetation and soils of regional watersheds and, consequently, to the streams that drain them.

Water quality programs that monitor and regulate these systems have to account for the influence of these factors upon water quality measurements when making monitoring and regulatory decisions. This is true for traditional water quality measures (nutrients, metals, contaminants, etc.), but is especially important for integrative ecological condition indicators like bioassessment, the use of resident biological communities to infer water quality condition.

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Estimating Exposure of Piscivorous Birds and Sport Fish to Mercury in California Lakes Using Prey Fish Monitoring—A Predictive Tool for Managers

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Estimating Exposure of Piscivorous Birds and Sport Fish to Mercury in California Lakes Using Prey Fish Monitoring—A Predictive Tool for Managers
U.S. Geological Survey (USGS) | May 22, 2015...
Summary
Numerous water bodies in California are listed under the Clean Water Act as being impaired due to mercury (Hg) contamination. The Surface Water...
Numerous water bodies in California are listed under the Clean Water Act as being impaired due to mercury (Hg) contamination. The Surface Water Ambient Monitoring Program (SWAMP), via the Bioaccumulation Oversight Group (BOG), has recently completed statewide surveys of contaminants in sport fish tissue from more than 250 lakes and rivers in California and throughout coastal waters. This effort focused on human health issues but did not include beneficial uses by wildlife. Many piscivorous birds such as grebes, terns, cormorants, and mergansers eat fish smaller than those that were sampled by BOG, and sport fish Hg concentrations are not always indicative of wildlife exposure to Hg; therefore, the BOG surveys could not address whether wildlife were at risk due to Hg-induced reproductive impairment in these lakes.

We used western grebes (Aechmophorus occidentalis) and Clark’s grebes (Aechmophorus clarkii) as our index of wildlife exposure to Hg in California lakes. Grebes are widely distributed in lakes throughout California and, as piscivorous waterbirds, are near the top of the food chain in lakes. Additionally, grebes become flightless after they arrive at their summer locations. Thus, grebes are useful representatives for wildlife risk from local, lake-specific contaminant exposure. Grebes also breed at many lakes throughout California, making them susceptible to impaired reproduction due to local Hg contamination.

We developed a tool for estimating wildlife and sport fish risk from Hg exposure based on Hg concentrations in prey fish. This quantitative tool can be used to predict Hg concentrations in grebe blood, grebe eggs, and sport fish, thus facilitating a feasible alternative for adequately estimating wildlife exposure when more comprehensive wildlife sampling is not possible. Specifically, we sampled grebes, prey fish, and sport fish simultaneously at 25 lakes throughout California during the spring and summer of 2012 and 2013 when breeding birds are particularly vulnerable to Hg-induced reproductive impairment. We selected lakes based on a combination of factors, including lakes
1. from southern and northern California,
2. of various sizes, shapes, and elevations,
3. with a range of sport fish Hg exposure levels
4. where largemouth bass (Micropterus salmoides) was the primary sport fish, and
5. with a history of use by grebes.
Using these factors ensured that our results are representative of a broad range of lakes and reservoirs in California and are comparable to prior BOG studies.

Specifically, we addressed three management questions:
1. Does methylmercury pose significant risks to aquatic life in a representative sample of California lakes and reservoirs?
2. Can a correlational approach be applied on a statewide basis to estimate risks to birds?
3. What are appropriate water-quality monitoring requirements to address methylmercury exposure in wildlife?
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Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California
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Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California
U.S. Geological Survey; California Regional Water Quality Control Board, Colorado River Basin Region | June 25, 1992...
Summary
A geohydrologic data base was compiled to evaluate the changes in ground-water conditions in the upper Coachella Valley, California, since 1978, when the...
A geohydrologic data base was compiled to evaluate the changes in ground-water conditions in the upper Coachella Valley, California, since 1978, when the results of a previous ground-water-model study were published. The compiled data were analyzed to improve understanding of the ground-water flow system and the effects on water quality of an existing artificial-recharge program. Analysis of well logs indicates that several zones of differing permeability can be correlated throughout the valley. Analysis of the water-quality data suggests that the artificial recharge of Colorado River water has caused increases in dissolved solids in some wells. Sparse data indicate that the recharged water moves much more rapidly through the uppermost part of the ground-water system than through deeper parts. An evaluation of the existing ground-water simulation model of the upper Coachella Valley that was developed in the 1978 study yielded several conclusions. First, the 300- to 400-foot rise in water levels in the artificialrecharge area in 1985-86 significantly affected the groundwater flow system. Transmissivities in the model had to be increased to reflect the increase in saturated thickness. Storage-coefficient values in the model had to be increased from 0.02 (used in the previous study) to 0.10-0.15 to simulate the unconfined water-level response during this period. Second, stream-recharge and underflow rates from San Gorgonio Pass during 1979-86 seem to have been higher than the values estimated for previous studies. Conditions generally were wetter in 1979-86 than during the period in which the earlier estimates were made. Third, the flow system could be simulated more accurately if the model were extended to its true southeastern boundary, the Salton Sea. Finally, there are important vertical differences in transport of the artificially recharged water that the two-dimensional areal transport model cannot simulate.

The study results indicate several additional data collection and modeling needs. The drilling of several sets of monitor wells perforated at different depths could help better define the three-dimensional flow system and waterquality differences. Additional data also are needed on underflow and stream recharge, evaporation rates and infiltration rates at the artificial-recharge facilities, and net pumpage. Three-dimensional flow and transport models are needed to evaluate the effects of ground-water development on water levels and water quality.

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A Field Guide to the Identification of the Ordinary High Water Mark (OHWM) in the Arid West Region of the Western United States: A Delineation Manual

A Field Guide to the Identification of the Ordinary High Water Mark (OHWM) in the Arid West Region of the Western United States: A Delineation Manual

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A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA

A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA

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A Water Resources Data-Network Evaluation for Monterey County, California, Phase 3: Northern Salinas River Drainage Basin

A Water Resources Data-Network Evaluation for Monterey County, California, Phase 3: Northern Salinas River Drainage Basin

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Adapting to Change: Utility Systems and Declining Flows

Adapting to Change: Utility Systems and Declining Flows

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Advancement of Salinity and Flow Monitoring in the San Francisco Bay Delta, San Francisco Bay Delta Action Plan Implementation Support, FINAL REPORT

Advancement of Salinity and Flow Monitoring in the San Francisco Bay Delta, San Francisco Bay Delta Action Plan Implementation Support, FINAL REPORT

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An Index of Biotic Integrity (IBI) for Perennial Streams in California’s Central Valley

An Index of Biotic Integrity (IBI) for Perennial Streams in California’s Central Valley

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

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

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Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life

Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life

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Biological Condition of Non-Perennial Streams and Spring-Fed Oases in the Colorado River Basin Region

Biological Condition of Non-Perennial Streams and Spring-Fed Oases in the Colorado River Basin Region

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Biology-based Stressor Thresholds

Biology-based Stressor Thresholds

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Bulletin No. 52-B Salinas Basin Investigation Summary Report

Bulletin No. 52-B Salinas Basin Investigation Summary Report

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Characterizing Nitrates in Central Coast Groundwater

Characterizing Nitrates in Central Coast Groundwater

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Comparison of the Performance of Different Bioassessment Methods: Similar Evaluations of Biotic Integrity from Separate Programs and Procedures

Comparison of the Performance of Different Bioassessment Methods: Similar Evaluations of Biotic Integrity from Separate Programs and Procedures

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Comparisons of Targeted-riffle and Reach-wide Benthic Macroinvertebrate Samples: Implications for Data Sharing in Stream-condition Assessments

Comparisons of Targeted-riffle and Reach-wide Benthic Macroinvertebrate Samples: Implications for Data Sharing in Stream-condition Assessments

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Condition of California Perennial, Wadeable Streams Based on Algal Indicators

Condition of California Perennial, Wadeable Streams Based on Algal Indicators

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Detections of current-use pesticides at 12 surface water sites in California during a 2-year period beginning in 2015

Detections of current-use pesticides at 12 surface water sites in California during a 2-year period beginning in 2015

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DRERIP Ecosystem Conceptual Model: Chemical stressors

DRERIP Ecosystem Conceptual Model: Chemical stressors

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Effects of wildfire on benthic macroinvertebrate assemblages in Southern California streams and implications for bioassessment monitoring programs

Effects of wildfire on benthic macroinvertebrate assemblages in Southern California streams and implications for bioassessment monitoring programs

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Estimating Exposure of Piscivorous Birds and Sport Fish to Mercury in California Lakes Using Prey Fish Monitoring—A Predictive Tool for Managers

Estimating Exposure of Piscivorous Birds and Sport Fish to Mercury in California Lakes Using Prey Fish Monitoring—A Predictive Tool for Managers

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Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California

Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California

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