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At least 415 records · Page 23Linked to original sources
USGS1994

An analysis of human-induced land transformations in the San Francisco Bay/Sacramento area

Part of the U.S. Geological Survey's Global Change Research Program involvesstudying the area from the Pacific Ocean to the Sierra foothills to enhance understanding ofthe role that human activities play in global change. The study investigates the ways thathumans transform the land and the effects that changing the landscape may have on regionaland global systems. To accomplish this research, scientists are compiling records ofhistorical transformations in the region's land cover over the last 140 years, developing asimulation model to predict land cover change, and assembling a digital data set to analyzeand describe land transformations. The historical data regarding urban growth focusattention on the significant change the region underwent from 1850 to 1990. Animation isused to visualize a time series of the change in land cover. The historical change is beingused to calibrate a prototype cellular automata model, developed to predict changes in urbanland cover 100 years into the future. Future urban growth scenarios will be developed foranalyzing possible human-induced impacts on land cover at a regional scale. These data aidin documenting and understanding human-induced land transformations from both historical andpredictive perspectives. A descriptive analysis of the region is used to investigate therelationships among data characteristic of the region. These data consist of multilayertopography, climate, vegetation, and population data for a 256-km2 region of centralCalifornia. A variety of multivariate analysis tools are used to integrate the data inraster format from map contours, interpolated climate observations, satellite observations,and population estimates.

World Resource Review↗
USGS1997

Techniques for estimating peak-streamflow frequency for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma

Statewide regression equations for Oklahoma were determined for estimating peak discharge and flood frequency for selected recurrence intervals from 2 to 500 years for ungaged sites on natural unregulated streams. The most significant independent variables required to estimate peak-streamflow frequency for natural unregulated streams in Oklahoma are contributing drainage area, main-channel slope, and mean-annual precipitation. The regression equations are applicable for watersheds with drainage areas less than 2,510 square miles that are not affected by regulation from manmade works. Limitations on the use of the regression relations and the reliability of regression estimates for natural unregulated streams are discussed. Log-Pearson Type III analysis information, basin and climatic characteristics, and the peak-stream-flow frequency estimates for 251 gaging stations in Oklahoma and adjacent states are listed. Techniques are presented to make a peak-streamflow frequency estimate for gaged sites on natural unregulated streams and to use this result to estimate a nearby ungaged site on the same stream. For ungaged sites on urban streams, an adjustment of the statewide regression equations for natural unregulated streams can be used to estimate peak-streamflow frequency. For ungaged sites on streams regulated by small floodwater retarding structures, an adjustment of the statewide regression equations for natural unregulated streams can be used to estimate peak-streamflow frequency. The statewide regression equations are adjusted by substituting the drainage area below the floodwater retarding structures, or drainage area that represents the percentage of the unregulated basin, in the contributing drainage area parameter to obtain peak-streamflow frequency estimates.

Oklahoma↗
USGS2014

1.13 – Emerging contaminants

Since the Industrial Revolution, a diversity of large-scale chemical innovations has impacted aquatic systems in urban environments. Beginning in the 1990s, there has been a growing scientific interest and public awareness of the effects of the chemicals used in domestic, commercial, industrial, and agricultural applications, referred to in this article as ‘emerging contaminants’ (ECs), on ecosystem and human health. The growing global population and its increasing demands on water supplies in conjunction with climate-induced changes in hydrologic regimes place stress on freshwater resources, resulting in a greater reliance on reuse of reclaimed municipal wastewater treatment plant (WWTP) effluents to meet human and environmental needs. WWTP effluents are a major source of ECs, and it is important to have an understanding of the chemical composition of the reclaimed water, because many ECs are biologically active and the effects of chronic exposure to low concentration complex mixtures are unknown. Several classes of ECs that have been shown to be widespread in the aquatic environment are discussed in this chapter, including surfactants, complexing agents, fragrances, antimicrobials, industrial chemicals, pharmaceuticals, natural and synthetic estrogens, and disinfection byproducts. All of these compounds are biologically active via a variety of modes of action, and can occur in aquatic systems at concentrations ranging from <0.001 to >100 μg l −1 .

Book chapter↗
USGS2012

Groundwater quality in the Antelope Valley, California

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Antelope Valley is one of the study areas being evaluated. The Antelope study area is approximately 1,600 square miles (4,144 square kilometers) and includes the Antelope Valley groundwater basin (California Department of Water Resources, 2003). Antelope Valley has an arid climate and is part of the Mojave Desert. Average annual rainfall is about 6 inches (15 centimeters). The study area has internal drainage, with runoff from the surrounding mountains draining towards dry lakebeds in the lower parts of the valley. Land use in the study area is approximately 68 percent (%) natural (mostly shrubland and grassland), 24% agricultural, and 8% urban. The primary crops are pasture and hay. The largest urban areas are the cities of Palmdale and Lancaster (2010 populations of 152,000 and 156,000, respectively). Groundwater in this basin is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay derived from surrounding mountains. The primary aquifers in Antelope Valley are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells in Antelope Valley are completed to depths between 360 and 700 feet (110 to 213 meters), consist of solid casing from the land surface to a depth of 180 to 350 feet (55 to 107 meters), and are screened or perforated below the solid casing. Recharge to the groundwater system is primarily runoff from the surrounding mountains, and by direct infiltration of irrigation and sewer and septic systems. The primary sources of discharge are pumping wells and evapotranspiration near the dry lakebeds.

California↗
USGS2021

Estimates of energy partitioning, evapotranspiration, and net ecosystem exchange of CO2 for an urban lawn and a tallgrass prairie in the Denver metropolitan area under contrasting conditions

Lawns as a landcover change substantially alter evapotranspiration, CO 2 , and energy exchanges and are of rising importance considering their spatial extent. We contrast eddy covariance (EC) flux measurements collected in the Denver, Colorado, USA metropolitan area in 2011 and 2012 over a lawn and a xeric tallgrass prairie. Close linkages between seasonal vegetation development, energy fluxes, and net ecosystem exchange ( NEE ) of CO 2 were found. Irrigation of the lawn modified energy and CO 2 fluxes and greatly contributed to differences observed between sites. Due to greater water inputs (precipitation + irrigation) at the lawn in this semi-arid climate, energy partitioning at the lawn was dominated by latent heat ( LE ) flux. As a result, evapotranspiration ( ET ) of the lawn was more than double that of tallgrass prairie (2011: 639(±17) mm vs. 302(±9) mm; 2012: 584(±15) mm vs. 265(±7) mm). NEE for the lawn was characterized by a longer growing season, higher daily net uptake of CO 2 , and growing season NEE that was also more than twice that of the prairie (2011: −173(±23) g C m −2 vs. -81(±10) g C m −2 ; 2012: −73(±22) g C m −2 vs. -21(±8) g C m −2 ). During the drought year (2012), temperature and water stress greatly influenced the direction and magnitude of CO 2 flux at both sites. The results suggest that lawns in Denver can function as carbon sinks and conditionally contribute to the mitigation of carbon emissions - directly by CO 2 uptake and indirectly through effects of evaporative cooling on microclimate and energy use.

Colorado↗
USGS2025

Seasonal stratification drives bioaccumulation of pelagic mercury sources in eutrophic lakes

Increased lake eutrophication, influenced by changing climate and land use, alters aquatic cycling and bioaccumulation of mercury (Hg). Additionally, seasonally dynamic lake circulation and plankton community composition can confound our ability to predict changes in biological Hg concentrations and sources. To assess temporal variation, we examined seasonal total Hg (THg) and methylmercury (MeHg) concentrations and stable isotope values in seston, waters, sediments, and fish from two adjacent urban eutrophic lakes in Madison, Wisconsin. In Lake Monona, surface sediment THg concentrations were elevated due to comparably higher urbanization and historical industrial inputs, whereas Lake Mendota sediments had lower concentrations corresponding with largely agricultural and suburban surrounding watershed. Surface water THg and MeHg were similar between lakes and seasonally dynamic, but water profiles exhibited elevated concentrations in the meta- and hypolimnion, highlighting water column MeHg production. Seston MeHg concentrations were often highest at shoulder seasons, possibly owing to metalimnetic MeHg delivery, but also differences in biomass and water clarity. The ∆199Hg and δ202Hg values in seston were similar between lakes, despite differing sediment THg concentrations and values, suggesting a shared bioaccumulated source of MeHg. Measurement of MeHg stable isotopes further elucidated that seston and fish predominantly bioaccumulated pelagic-sourced MeHg.

Wisconsin↗
USGS2015

Groundwater quality in the Northern Coast Ranges Basins, California

The Northern Coast Ranges (NOCO) study unit is 633 square miles and consists of 35 groundwater basins and subbasins (California Department of Water Resources, 2003; Mathany and Belitz, 2015). These basins and subbasins were grouped into two study areas based primarily on locality. The groundwater basins and subbasins located inland, not adjacent to the Pacific Ocean, were aggregated into the Interior Basins (NOCO-IN) study area. The groundwater basins and subbasins adjacent to the Pacific Ocean were aggregated into the Coastal Basins (NOCO-CO) study area (Mathany and others, 2011). The primary aquifer system in the NOCO-IN study area occurs in alluvial basins made up of sand, silt, gravel, clay, and thin volcanic ash layers or lenses. Groundwater movement in the NOCO-IN study area follows the topography and direction of surface-water features. In the NOCO-CO study area, groundwater is present in alluvial fan, floodplain, and terrace deposits. Groundwater movement in the NOCO-CO study area is from east to west towards the Pacific Ocean. The primary aquifer system in the study unit generally is defined as those parts of the aquifer system corresponding to the perforated intervals of sites listed in the California Department of Public Health (CDPH) database of public drinking-water supply sources. Well depths in the NOCO-IN study area ranged from 36 to 400 feet below land surface (ft bls), and depths to top-of-perforations ranged from 15 to 148 ft bls. In the NOCO-CO study area, well depths ranged from 15 to 400 ft bls, and depths to top-of-perforations ranged from 10 to 356 ft bls. Water quality in the primary aquifer system may differ from that in the shallower and deeper parts of the aquifer system. Average annual rainfall in the NOCO study unit ranges from 22 to 79 inches. In the NOCO-IN study area, the climate is classified as Mediterranean, with warm to hot, dry summers and cold, wet winters. In the NOCO-CO study area, the climate is influenced by the Pacific Ocean and is characterized by cool to mild summers and cold, wet winters. The study unit is drained by several rivers and their principal tributaries: the Eel, Russian, Mad, Navarro, Smith, Klamath, Noyo, and Big Rivers. Land use in the study unit is about 60 percent (%) natural (mostly grassland and forest), 29% agricultural, and 11% urban. The primary uses of agricultural lands are pasture, row crops, hay, vineyards, and timberlands. The largest urban areas are the cities of Crescent City, Arcata, Eureka, Fort Bragg, Willits, Ukiah, and Lakeport. Recharge to the groundwater system is primarily from mixture of ambient sources, including direct percolation of precipitation and irrigation waters, infiltration of runoff from surrounding hills/areas, seepage from rivers and creeks, and subsurface inflow (from non-alluvial geologic units that bound the alluvial basins). The primary sources of discharge are evaporation, discharge to streams, and water pumped for municipal supply and irrigation.

California↗
USGS1977

Techniques for estimating flood discharges for Oklahoma streams; Techniques for calculating magnitude and frequency of floods in Oklahoma from rural and urban areas under 2500 square miles, with compilations of flood data through 1975

Statewide regression equations are defined for estimating peak discharges of floods having recurrence intervals ranging from 2 to 500 years. Contributing drainage area, main-channel slope and mean annual precipitation are the independent variables required for estimating flood discharges for rural streams. For urban streams the percentage of the basin that is impervious and served by storm sewers also is required. The regression equations are applicable for watersheds draining less than 2,500 mil (6,500 km2) that are not significantly affected by regulation. For the rural streams, the regression equations are presented in graphical form for easy application. Annual peak data, basin and climatic characteristics, log-Pearson Type III statistics and the flood-frequency relations are presented for 188 gaging stations.

Oklahoma↗
USGS2012

Preliminary investigation of the effects of sea-level rise on groundwater levels in New Haven, Connecticut

Global sea level rose about 0.56 feet (ft) (170 millimeters (mm)) during the 20th century. Since the 1960s, sea level has risen at Bridgeport, Connecticut, about 0.38 ft (115 mm), at a rate of 0.008 ft (2.56 mm + or - 0.58 mm) per year. With regional subsidence, and with predicted global climate change, sea level is expected to continue to rise along the northeast coast of the United States through the 21st century. Increasing sea levels will cause groundwater levels in coastal areas to rise in order to adjust to the new conditions. Some regional climate models predict wetter climate in the northeastern United States under some scenarios. Scenarios for the resulting higher groundwater levels have the potential to inundate underground infrastructure in lowlying coastal cities. New Haven is a coastal city in Connecticut surrounded and bisected by tidally affected waters. Monitoring of water levels in wells in New Haven from August 2009 to July 2010 indicates the complex effects of urban influence on groundwater levels. The response of groundwater levels to recharge and season varied considerably from well to well. Groundwater temperatures varied seasonally, but were warmer than what was typical for Connecticut, and they seem to reflect the influence of the urban setting, including the effects of conduits for underground utilities. Specific conductance was elevated in many of the wells, indicating the influence of urban activities or seawater in Long Island Sound. A preliminary steady-state model of groundwater flow for part of New Haven was constructed using MODFLOW to simulate current groundwater levels (2009-2010) and future groundwater levels based on scenarios with a rise of 3 ft (0.91 meters (m)) in sea level, which is predicted for the end of the 21st century. An additional simulation was run assuming a 3-ft rise in sea level combined with a 12-percent increase in groundwater recharge. The model was constructed from existing hydrogeologic information for the New Haven area and from new information on groundwater levels collected during October 2009-June 2010. For the scenario with a 3-ft rise in sea level and no increase in recharge, simulated groundwater levels near the coast rose 3 ft; this increased water level tapered off toward a discharge area at the only nontidal stream in the study area. Simulated stream discharge increased at the nontidal stream because of the increased gradient. Although groundwater levels rose, the simulated difference between the groundwater levels in the aquifer and the increased sea level declined, indicating that the depth to the interface between freshwater and saltwater may possibly decline. Simulated water levels were affected by rise in sea level even in areas where the water table was at 17-24 ft (5.2-7.3 m) above current (2011) sea level. For the scenario with increased recharge, simulated groundwater levels were as much as an additional foot higher at some locations in the study area. The results of this preliminary investigation indicate that groundwater levels in coastal areas can be expected to rise and may rise higher if groundwater recharge also increases. This finding has implications for the disposal of stormwater through infiltration, a low-impact development practice designed to improve water quality and reduce overland peak discharge. Other implications include increased risk of basement flooding and increased groundwater seepage into underground sewer pipes and utility corridors in some areas. These implications will present engineering challenges to New Haven and Yale University. The preliminary model developed for this study can be the starting point for further simulation of future alternative scenarios for sea-level rise and recharge. Further simulations could identify those areas of New Haven where infrastructure may be at greatest risk from rising levels of groundwater. The simulations described in this report have limitations due to the preliminary scope of the work. Approaches to improve simulations include but are not limited to incorporating: * The variable density of seawater into the model in order to understand the current and future location of the interface between freshwater and saltwater; * Collection of additional data in order to better resolve temporal and spatial patterns in water levels in the aquifer; * Improved estimates of recharge through direct and indirect measurements of freshwater discharge from the study area; and * Transient simulations for greater understanding of the amount of time required for water levels and the position of the interface between freshwater and saltwater to adjust to changes in sea level and recharge.

Connecticut↗
USGS2007

A simple daily soil-water balance model for estimating the spatial and temporal distribution of groundwater recharge in temperate humid areas

Quantifying the spatial and temporal distribution of natural groundwater recharge is usually a prerequisite for effective groundwater modeling and management. As flow models become increasingly utilized for management decisions, there is an increased need for simple, practical methods to delineate recharge zones and quantify recharge rates. Existing models for estimating recharge distributions are data intensive, require extensive parameterization, and take a significant investment of time in order to establish. The Wisconsin Geological and Natural History Survey (WGNHS) has developed a simple daily soil-water balance (SWB) model that uses readily available soil, land cover, topographic, and climatic data in conjunction with a geographic information system (GIS) to estimate the temporal and spatial distribution of groundwater recharge at the watershed scale for temperate humid areas. To demonstrate the methodology and the applicability and performance of the model, two case studies are presented: one for the forested Trout Lake watershed of north central Wisconsin, USA and the other for the urban-agricultural Pheasant Branch Creek watershed of south central Wisconsin, USA. Overall, the SWB model performs well and presents modelers and planners with a practical tool for providing recharge estimates for modeling and water resource planning purposes in humid areas. ?? Springer-Verlag 2007.

Hydrogeology Journal↗
USGS2016

A century of landscape disturbance and urbanization of the San Francisco Bay region affects the present-day genetic diversity of the California Ridgway’s rail (Rallus obsoletus obsoletus)

Fragmentation and loss of natural habitat have important consequences for wild populations and can negatively affect long-term viability and resilience to environmental change. Salt marsh obligate species, such as those that occupy the San Francisco Bay Estuary in western North America, occupy already impaired habitats as result of human development and modifications and are highly susceptible to increased habitat loss and fragmentation due to global climate change. We examined the genetic variation of the California Ridgway’s rail ( Rallus obsoletus obsoletus ), a state and federally endangered species that occurs within the fragmented salt marsh of the San Francisco Bay Estuary. We genotyped 107 rails across 11 microsatellite loci and a single mitochondrial gene to estimate genetic diversity and population structure among seven salt marsh fragments and assessed demographic connectivity by inferring patterns of gene flow and migration rates. We found pronounced genetic structuring among four geographically separate genetic clusters across the San Francisco Bay. Gene flow analyses supported a stepping stone model of gene flow from south-to-north. However, contemporary gene flow among the regional embayments was low. Genetic diversity among occupied salt marshes and genetic clusters were not significantly different. We detected low effective population sizes and significantly high relatedness among individuals within salt marshes. Preserving genetic diversity and connectivity throughout the San Francisco Bay may require attention to salt marsh restoration in the Central Bay where habitat is both most limited and most fragmented. Incorporating periodic genetic sampling into the management regime may help evaluate population trends and guide long-term management priorities.

California↗
USGS2018

Factors affecting long-term trends in surface-water quality in the Gwynns Falls watershed, Baltimore City and County, Maryland, 1998–2016

Factors affecting water-quality trends in urban streams are not well understood, despite current regulatory requirements and considerable ongoing investments in gray and green infrastructure. To address this gap, long-term water-quality trends and factors affecting these trends were examined in the Gwynns Falls, Maryland, watershed during 1998–2016 in cooperation with Blue Water Baltimore. Data on water-quality constituents and potential factors of influence were obtained from multiple sources and compiled for analysis, with a focus on data collected as part of the National Science Foundation funded Long-Term Ecological Research project, the Baltimore Ecosystem Study. Variability in climate (specifically, precipitation) and land cover can overwhelm actions taken to improve water quality and can present challenges for meeting regulatory goals. Analysis of land cover during 2001–11 in the Gwynns Falls watershed indicated minimal change during the study time frame; therefore, land-cover change is likely not a factor affecting trends in water quality. However, a modest increase in annual precipitation and a significant increase in winter precipitation were apparent in the region. A higher proportion of runoff producing storms was observed in the winter and a lower proportion in the summer, indicating that climate change may affect water quality in the watershed. The increase in precipitation was not reflected in annual or seasonal trends of streamflow in the watershed. Nonetheless, these precipitation changes may exacerbate the inflow and infiltration of water to gray infrastructure and reduce the effectiveness of green infrastructure. For streamflow and most water-quality constituents examined, no discernable trends were noted over the timeframe examined. Despite the increases in precipitation, no trends were observed for annual or seasonal discharge at the various sites within the study area. In some locations, nitrate, phosphate, and total nitrogen show downward trends, and total phosphorus and chloride show upward trends. Sanitary sewer overflows (gray infrastructure) and best management practices (green infrastructure) were identified as factors affecting water-quality change. The duration of sanitary sewer overflows was positively correlated with annual loads of nutrients and bacteria, and the drainage area of best management practices was negatively correlated with annual loads of phosphate and sulfate. Results of the study indicate that continued investments in gray and green infrastructure are necessary for urban water-quality improvement. Although this outcome is not unexpected, long-term datasets such as the one used in this study, allow the effects of gray and green infrastructures to be quantified. Results of this study have implications for the Gwynns Falls watershed and its residents and Baltimore City and County managers. Moreover, outcomes are relevant to other watersheds in the metropolitan region that do not have the same long-term dataset. Further, this study has established a framework for ongoing statistical analysis of primary factors affecting urban water-quality trends as regulatory programs mature.

Maryland↗
USGS2023

Simulating the migration dynamics of juvenile salmonids through rivers and estuaries using a hydrodynamically driven enhanced particle tracking model

Juvenile salmonids migrate hundreds of kilometers from their natal streams to mature in the ocean. Throughout this migration, they respond to environmental cues such as local water velocities and other stimuli to direct and modulate their movements, often through heavily modified riverine and estuarine habitats. Management strategies in an uncertain future of climate change and altered land use regimes depend heavily on being able to reliably predict their ocean entry timings, route use, and survival rates through rivers and estuaries. We developed a spatially-explicit agent-based model of fish movement in response to hydrodynamic flows that uses movement dynamics gleaned from multi-dimensional tracking datasets of acoustically tagged juveniles moving through an urbanized, branched tidal estuary. We demonstrate how such models can be calibrated, and we apply it to the Sacramento-San Joaquin Delta in Central California. The quality of the out-of-sample validation of the model to predict juvenile salmon survival and route selection indicates that the model is versatile and flexible enough to be used in novel hydroclimatological conditions.

California↗
USGS2001

Selected findings and current perspectives on urban and agricultural water quality by the National Water-Quality Assessment Program

Studies by the USGS National Water-Quality Assessment (NAWQA) program in the last decade describe water-quality conditions in nearly 120 agricultural and 35 urban watersheds ('urban' primarily refers to residential and commercial development over the last 50 years). The findings show that for both urban and agricultural areas, nonpoint chemical contamination is an issue. Much work still needs to be done in urban areas with point source contamination as well, including infrastructure improvements. Appreciable improvements in overall water quality, however, will depend upon effective management of point and nonpoint sources. The findings show that nonpoint chemical contamination is an agricultural and urban issue. Whereas a lot of work still needs to be pursued with point source contamination and infrastructure improvements in urban areas (such as related to combined and sanitary sewer overflows), appreciable improvements in water quality also will depend upon management of nonpoint sources. The NAWQA findings also show that water-quality conditions and aquatic health reflect a complex combination of land and chemical use, land-management practices, population density and watershed development, and natural features, such as soils, geology, hydrology, and climate. Contaminant concentrations vary from season to season and from watershed to watershed. Even among seemingly similar land uses and sources of contamination, different areas can have very different degrees of vulnerability and, therefore, have different rates at which improved treatment or management can lead to water-quality improvements.

Fact Sheet↗
USGS2018

Population genomic surveys for six rare plant species in San Diego County, California

San Diego County is a hotspot of biodiversity, situated at the intersection of the Baja peninsula, the California floristic province, and the desert southwest. This hotspot is characterized by a high number of rare and endemic species, which persist alongside a major urban epicenter. San Diego County has implemented a strategic management plan that identifies species, based on low numbers of occurrences or high level of threat, for which management practices are recommended. In creating a management plan for rare species, it is important to strike a balance between preserving locally adapted traits and maintaining genetic diversity, as species’ ranges fluctuate in response to a changing climate and habitat fragmentation. This project, in partnership with the San Diego Natural History Museum, aims to provide a reference point for the current status of genetic diversity of rare plant species that will inform future preservation and restoration efforts. We focused on six threatened or endangered plant species: Acanthomintha ilicifolia , Baccharis vanessae , Chloropyron maritimum ssp. maritimum , Deinandra conjugens , Dicranostegia orcuttiana , and Monardella viminea . For each species, botanists from the San Diego Natural History Museum visited all known occurrences in San Diego County and collected leaf tissue for genetic and cytological analysis. We then developed a panel of genetic markers to estimate genetic diversity and population structure. This population genetic survey provided insight into the amount of genetic differentiation across each species’ range, identified isolated occurrences potentially subject to inbreeding or genetic bottlenecks, and identified areas that are rich sources of allelic diversity. Finally, we convened a panel of experts to review results and compatible management options for each species. A summary of the management workshop is included in this report. Overall, we found low genetic differentiation among occurrences across the San Diego region for all species, with the exception of A. ilicifolia . Relative inbreeding was low and consistent across sites, and genetic diversity across sites was variable, with noted exceptions. These findings allow for a wide array of management options that are compatible with panmictic population structure in five of the six surveyed species.

California↗
USGS2025

Marshes to mangroves: Residential surveys reveal perceived wetland trade-offs for ecosystem services

Coastal landscapes are rapidly changing due to both climate change and the decisions of waterfront landowners. For instance, the climate-driven encroachment of woody mangrove species into grassy marshland areas is predicted to impact coastal ecosystems, with consequences for the ecosystem services these landscapes provide to people. However, there is a dearth of knowledge concerning coastal resident perceptions of the effects of mangrove expansion on wetlands and their ecosystem services, which may impact residents’ behavior around shorelines and landscape-level patterns. We surveyed waterfront residents in the northern Gulf of Mexico (USA) to understand perceptions of the relative performance of marshes and mangroves to deliver fisheries ecosystem services. Residential-scale shoreline condition and preference, recreational fishing activity, geography, and demographics were evaluated as potential predictors of resident perceptions through non-parametric comparisons across groups and ordered logit modeling. Significant predictors included area of residence, marsh shoreline condition, marsh shoreline preference, fishing frequency, and household income. Florida residents (where mangroves are most prevalent) and frequent recreational fishing participants exhibited stronger preference for mangroves. Unexpectedly, residents with marsh currently present on their shoreline also perceived that mangroves were better at delivering fisheries ecosystem services than marshes. Considering the important role that coastal residents play in shoreline management decisions, these results demonstrate how coastal resident attitudes may drive or mediate climate-driven processes in ways that are not evident by examining environmental conditions alone. Understanding social-ecological shifts due to climate change will be important to inform effective landscape management that promotes resilience in coastal ecosystems and societies.

Landscape and Urban Planning↗
USGS1973

Preliminary photointerpretation map of landslide and other surficial deposits of the Concord 15-minute quadrangle and the Oakland West, Richmond, and part of the San Quentin 7 1/2-minute quadrangles, Contra Costa and Alameda Counties, California

This map presents preliminary information about one aspect of the physical environment necessary to sound land-use planning- the nature and distribution of surficial deposits. Because surficial deposits are common and well developed in much of the bay region, it is useful to know how and why they have formed, as well as what properties they possess. When maps like this are used in combinaion with other types of environmental information, such as data on soils, bedrock geology, slopes, vegetation, climatic variation, seismic response, and hydrology, it should be easier to arrive at sound decisions regarding the physical aspects of land use. The U.S. Geological Survey is studying many of these factors in the bay region and hopes to provide the community with much of the required information as part of its San Francisco Bay Region Study in cooperation with the Department of Housing and Urban Development.

California↗
USGS1995

Environmental Setting and Implications on Water Quality, Upper Colorado River Basin, Colorado and Utah

The Upper Colorado River Basin in Colorado and Utah is 1 of 60 study units selected for water-quality assessment as part of the U.S. Geological Survey's National Water-Quality Assessment program, which began full implementation in 1991. Understanding the environmental setting of the Upper Colorado River Basin study unit is important in evaluating water-quality issues in the basin. Natural and human factors that affect water quality in the basin are presented, including an overview of the physiography, climatic conditions, general geology and soils, ecoregions, population, land use, water management and use, hydrologic characteristics, and to the extent possible aquatic biology. These factors have substantial implications on water-quality conditions in the basin. For example, high concentrations of dissolved solids and selenium are present in the natural background water conditions of surface and ground water in parts ofthe basin. In addition, mining, urban, and agricultural land and water uses result in the presence of certain constituents in the surface and ground water of the basin that can detrimentally affect water quality. The environmental setting of the study unit provides a framework of the basin characteristics, which is important in the design of integrated studies of surface water, ground water, and biology.

Water-Resources Investigations Report↗