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An article in the summer 1993 Newsletter described USGS work to continously monitor tidal flows in the delta using ultrasonic velocity meters. This article updates progress since 1993, including new installations, results of data analysis, damage during this year's high flows, and the status of each site.
No abstract available.
Specific conductance and water temperature data are continuously recorded at four sites in San Francisco Bay, California: San Pablo Strait at Point San Pablo, Central San Francisco Bay at Presidio Military Reservation, Pier 24 at Bay Bridge, and South San Francisco Bay at San Mateo Bridge near Foster City (Figure 1). Water level data are recorded only at San Pablo Strait at Point San Pablo. These data were recorded by the Department of Water Resources (DWR) before 1988, by the US Geological Survey (USGS) National Research Program from 1988 to 1989, and by the USGS-DWR cooperative program since 1990. This article presents time-series plots of data from the four sites in San Francisco Bay during water year 1998 (1 October 1997 through 30 September 1998).
Salinity and temperature are crucial state variables affecting estuarine habitat an d, thus, are measured by various San Francisco Estuary programs. This article presents a comparison of salinity and temperature data collected at seven continuo us monitoring stations throughout San Francisco Bay (Figure 1) with data collected monthly by the US Geological Survey (USGS) research vessel ( RV ) Polaris . The data comparison was done to determine if the continuous monitoring stations, which mostly are located near shore and always on structures in the water, are representative of water conditions in the main channel of the estuary where the RV Polaris collects measurements.
No abstract available
Time series of water-level, specific-conductance, and watertemperature data were collected at seven sites in San Francisco Bay during water year 2000 (October 1, 1999 through September 30, 2000). Water-level data were recorded only at Point San Pablo. Specific-conductance and water-temperature data were recorded at 15-minute intervals at the following locations (Figure 1): • Carquinez Strait at Carquinez Bridge • Napa River at Mare Island Causeway near Vallejo • San Pablo Bay at Petaluma River Channel Marker 9 • San Pablo Strait at Point San Pablo • Central San Francisco Bay at Presidio Military Reservation • Central San Francisco Bay at Pier 24 • South San Francisco Bay at San Mateo Bridge near Foster City.
This article presents time-series plots of specific-conductance, water-temperature, and water-level data collected in San Francisco Bay during water years 2001 and 2002 (October 1, 2000, through September 30, 2002). Specific-conductance and water-temperature data were recorded at 15-minute intervals at the following US Geological Survey (USGS) locations (Figure 1): • Suisun Bay at Benicia Bridge, near Benicia, California (BEN) (site # 11455780) • Carquinez Strait at Carquinez Bridge, near Crockett, California (CARQ) (site # 11455820) • Napa River at Mare Island Causeway, near Vallejo, California (NAP) (site # 11458370) • San Pablo Strait at Point San Pablo, California (PSP) (site # 11181360) • San Pablo Bay at Petaluma River Channel Marker 9, California (SPB) (site # 380519122262901) • San Francisco Bay at Presidio Military Reservation, California (PRES) (site # 11162690) • San Francisco Bay at Pier 24, at San Francisco, California (P24) (site # 11162700) • San Francisco Bay at San Mateo Bridge, near Foster City, California (SMB) (site # 11162765). Water-level data were recorded only at PSP through January 1, 2001. Suspended-sediment concentration data also were collected at most of these sites and were published by Buchanan and Ganju (2003). The data from PSP, PRES, P24, and SMB were recorded by the California Department of Water Resources (DWR) before 1988, by the USGS National Research Program from 1988 to 1989, and by the USGSDWR cooperative program since 1990. BEN, CARQ, NAP, and SPB were established in 1998 by the USGS.
This article presents time-series graphs of specific-conductance and water-temperature data collected in San Francisco Bay during water year 2003 (October 1, 2002, through September 30, 2003). Specific-conductance and water-temperature data were recorded at 15-minute intervals at the following US Geological Survey (USGS) locations (Figure 1): • Suisun Bay at Benicia Bridge, near Benicia, CA. (BEN) (site # 11455780) • Carquinez Strait at Carquinez Bridge, near Crockett, CA. (CARQ) (site # 11455820) • Napa River at Mare Island Causeway, near Vallejo, CA. (NAP) (site # 11458370) • San Pablo Strait at Point San Pablo, CA. (PSP) (site # 11181360) • San Pablo Bay at Petaluma River Channel Marker 9, CA. (SPB) (site # 380519122262901) • San Francisco Bay at Presidio Military Reservation, CA. (PRES) (site # 11162690) • San Francisco Bay at San Mateo Bridge, near Foster City, CA. (SMB) (site # 11162765) Suspended-sediment-concentration data also were collected at most of these sites during water year 2003. Specific-conductance and water-temperature data from PSP, PRES, and SMB were recorded by the CA Department of Water Resources (DWR) before 1988, by the USGS National Research Program from 1988 to 1989, and by the USGS-DWR cooperative program since 1990. BEN, CARQ, NAP, and SPB were established in 1998 by USGS. The monitoring station at PRES was discontinued on November 12, 2002, due to shoaling at the site.
This article presents time-series graphs of specificconductance and water-temperature data collected in San Francisco Bay during water year 2004 (October 1, 2003, through September 30, 2004). Specific-conductance and water-temperature data were recorded at 15-minute intervals at seven U.S. Geological Survey (USGS) locations (Figure 1, Table 1). Specific-conductance and water-temperature data from Point San Pablo (PSP) and San Mateo Bridge (SMB) were recorded by the California Department of Water Resources (DWR) before 1988, by the USGS National Research Program from 1988 to 1989, and by the USGSDWR cooperative program since 1990. Benicia Bridge (BEN), Carquinez Bridge (CARQ), and Napa River (NAP) were established in 1998 by the USGS. San Pablo Bay (SPB) was initially established in 1998 at Channel Marker 9 but was moved to Channel Marker 1 in 2003. The monitoring station at Alcatraz (ALC) was established in 2003 by the USGS to replace the discontinued monitoring station San Francisco Bay at Presidio Military Reservation.
This article presents an overview of recent findings from hydrodynamic research on circulation and mixing in the Sacramento-San Joaquin Delta (Delta) (Figure 1) and North San Francisco Bay (North Bay) (Figure 2). For the purposes of this article, North Bay includes San Pablo Bay, Carquinez Strait, and Suisun Bay. The findings presented are those gained from field studies carried out by the U.S. Geological Survey (USGS), as part of the Interagency Ecological Program (IEP), and Stanford University beginning about 1993. The premise behind these studies was that a basic understanding of circulation and mixing patterns in the Bay and Delta is an essential part of understanding how biota and water quality are affected by natural hydrologic variability, water appropriation, and development activities. Data collected for the field studies described in this article have significantly improved our understanding of Bay and Delta hydrodynamics. Measured flows ,in the Delta have provided valuable information on how water moves through the Delta's network of channels and how export pumping affects flows. Studies of the shallows and shallow-channel exchange processes conducted in Honker Bay have shown that the water residence time in Honker Bay is much shorter than previously reported (on the order of hours to several tidal cycles instead ofweeks). Suisun Bay studies have provided data on hydrodynamic transport and accumulation mechanisms that operate primarily in the channels. The Suisun Bay studies have caused us to revise our understanding of residual circulation in the channels of North Bay and of "entrapment" mechanisms in the low salinity zone. Finally, detailed tidal and residual (tidally averaged) time-scale studies of the mechanisms that control gravitational circulation in the estuary show that density-driven transport in the channels is governed by turbulence time-scale (seconds) interactions between the mean flow and stratification. The hydrodynamic research summarized in this article spans a range of estuarine environments (deep water channels to shallow water habitats and brackish water to freshwater) at time scales that range from seconds to years.
The small Asian clam, Potamocorbula amurensis , is now a major component of benthic communities in most areas of northern San Francisco Bay and some areas of South Bay. Because of its wide tolerance of salinity and other environmental variables and its high abundance in many areas, benthic ecologists believe this recent invasion may represent a major and permanent change in the bay system.
No abstract available.
The U.S. Geological Survey, Bureau of Reclamation, and the California Department of Water Resources maintain a large number of monitoring stations that record specific conductance, often referred to as “electrical conductivity,” in San Francisco Bay Estuary and the Sacramento-San Joaquin Delta. Specific conductance units that have been normalized to a standard temperature are useful in fresh waters, but conversion to salinity units has some considerable advantages in brackish waters of the estuary and Delta. For example, salinity is linearly related to the mixing ratio of freshwater and seawater, which is not the case for specific conductance, even when values are normalized to a standard temperature. The Practical Salinity Scale 1978 is based on specific conductance, temperature, and pressure measurements of seawater and freshwater mixtures (Lewis 1980 and references therein). Equations and data that define the scale make possible conversions between specific conductance and salinity values. This article presents a simplified conversion to salinity units for use with specific conductance data from monitoring stations that have been normalized to a standard temperature of 25 °C and an equation for the reverse calculation. Although these previously undocumented methods have been shared with many IEP agencies over the last two decades, the sources of the equations and data are identified here so that the original literature can be accessed.
A spring runoff pulse is identified in the Merced River record from the Sierra Nevada, that makes the transition from low streamflow conditions in winter to the high streamflow conditions in the later spring-early summer period. The timing of the pulse is delayed with greater seasonal accumulation of snow pack in the Yosemite region. Also, the runoff pulse is triggered by a regional weather fluctuation that establishes a warm high pressure ridge over the California region during the spring (mid-March to Mid-May) period. Since this ridge often blankets the entire western United States, it is found that a simultaneous pulse occurs over a broad collection of high-elevation streams in the region.
During the early 1990s (but echoing studies by S.T. Harding at the University of California, from as early as the 1930s), several lines of paleoclimate evidence in and around the Sierra Nevada Range have provided the water community in California with some real horror stories. By studying ancient tree stumps submerged in Lake Tahoe and Tenaya Lake, stumps that were emerging from Mono Lake during its recent decline, and stumps that were exhumed in the Walker River bed during the floods of 1997, paleoclimatologists like Scott Stine of California State University, Hayward, assembled a picture of epic droughts in the central Sierra Nevada during the medieval period. These droughts had to be severe to drop water levels in the lakes and rivers low enough for the trees to grow in the first place, and then had to last for hundreds of years to explain tree-ring counts in these sizeable stumps. Worse yet, the evidence suggested at least two such epic droughts, one ending close to 1100 and the other close to 1350. These epic droughts challenged paleoclimatologists, as well as modern climatologists and hydrologists, to understand and, ultimately, to determine the likelihood that such droughts might recur in the foreseeable future. The first challenge, however, was to verify that such droughts were more than local events and as extreme as suggested. At this year’s Pacific Climate (PACLIM) Workshop, held March 18–21, 2001, at Asilomar (Pacific Grove, Calif.), special sessions brought together scientists to compare paleoclimatic reconstructions of ancient droughts and pluvial (wet) epidodes to try to determine the nature of decadal and centennial climate fluctuations in western North America, with emphasis on California. A companion session brought together modern climatologists to report on the latest explanations (and evidence) for decadal climate variations during the instrumental era of the 20th century.
Benthic invertebrates play an important role in estuarine food webs and biogeochemical cycling of carbon, nutrients, and contaminants. The generally sedentary benthic invertebrates continuously integrate local water, sediment, and food conditions. This makes them good indicators of the type and quality of aquatic habitat at the location where they are found. The Interagency Ecological Program’s Environmental Monitoring Program (EMP) has monitored benthic invertebrates since the mid-1970s. A recent review of the EMP found that the spatial study design of the benthos monitoring element was in need of a thorough reexamination through intense special studies and extensive historic data analyses. This article reports the results of preliminary analyses of historical EMP data focusing on cross-channel variability. Specific questions are: (1) do benthic habitats and community assemblages vary between positions across a river channel? (2) Are benthic samples taken at a single channel position sufficiently representative of benthos assemblages across the channel to characterize long term changes in the benthos community of a particular section of a river?
The purpose of this study was to develop a twice-a-day sampling strategy for suspended solids concentration at Mallard Island that best reproduces the residual (tidally averaged) near-surface suspended solids concentration computed using the entire time series (96 sampling times per day) for high delta discharge conditions and to use this stratgy for sampling sediment-associated pesticides vvaried in a similar manner to suspended solids concentration would also be the optimum sampling strategy for sediment-associated pseticides.