David Schoellhamer (Former Employee)
Science and Products
Filter Total Items: 151
Projected evolution of California's San Francisco bay-delta-river system in a century of climate change
Background: Accumulating evidence shows that the planet is warming as a response to human emissions of greenhouse gases. Strategies of adaptation to climate change will require quantitative projections of how altered regional patterns of temperature, precipitation and sea level could cascade to provoke local impacts such as modified water supplies, increasing risks of coastal flooding, and growing
Authors
James E. Cloern, Noah Knowles, Larry R. Brown, Daniel R. Cayan, Michael D. Dettinger, Tara L. Morgan, David H. Schoellhamer, Mark T. Stacey, Mick Van der Wegen, R.W. Wagner, Alan D. Jassby
Continuous salinity and temperature data from San Francisco estuary, 1982-2002: Trends and the salinity-freshwater inflow relationship
The U.S. Geological Survey and other federal and state agencies have been collecting continuous temperature and salinity data, two critical estuarine habitat variables, throughout San Francisco estuary for over two decades. Although this dynamic, highly variable system has been well studied, many questions remain relating to the effects of freshwater inflow and other physical and biological linkag
Authors
Gregory Shellenbarger, David H. Schoellhamer
Measuring sediment accretion in early tidal marsh restoration
Sediment accretion is a critical indicator of initial progress in tidal marsh restoration. However, it is often difficult to measure early deposition rates, because the bottom surface is usually obscured under turbid, tidally-influenced waters. To accurately measure early sediment deposition in marshes, we developed an echosounder system consisting of a specialized acoustic profiler, differential
Authors
John Y. Takekawa, Isa Woo, Nicole D. Athearn, Scott A. Demers, Rachel J. Gardiner, William M. Perry, Neil K. Ganju, Gregory Shellenbarger, David H. Schoellhamer
Decadal-timescale estuarine geomorphic change under future scenarios of climate and sediment supply
Future estuarine geomorphic change, in response to climate change, sea-level rise, and watershed sediment supply, may govern ecological function, navigation, and water quality. We estimated geomorphic changes in Suisun Bay, CA, under four scenarios using a tidal-timescale hydrodynamic/sediment transport model. Computational expense and data needs were reduced using the morphological hydrograph con
Authors
N. K. Ganju, D. H. Schoellhamer
A Tidally Averaged Sediment-Transport Model for San Francisco Bay, California
A tidally averaged sediment-transport model of San Francisco Bay was incorporated into a tidally averaged salinity box model previously developed and calibrated using salinity, a conservative tracer (Uncles and Peterson, 1995; Knowles, 1996). The Bay is represented in the model by 50 segments composed of two layers: one representing the channel (>5-meter depth) and the other the shallows (0- to 5-
Authors
Megan A. Lionberger, David H. Schoellhamer
Hindcasting of decadal‐timescale estuarine bathymetric change with a tidal‐timescale model
Hindcasting decadal-timescale bathymetric change in estuaries is prone to error due to limited data for initial conditions, boundary forcing, and calibration; computational limitations further hinder efforts. We developed and calibrated a tidal-timescale model to bathymetric change in Suisun Bay, California, over the 1867–1887 period. A general, multiple-timescale calibration ensured robustness ov
Authors
Neil K. Ganju, David H. Schoellhamer, Bruce E. Jaffe
Calibration of an estuarine sediment transport model to sediment fluxes as an intermediate step for simulation of geomorphic evolution
Modeling geomorphic evolution in estuaries is necessary to model the fate of legacy contaminants in the bed sediment and the effect of climate change, watershed alterations, sea level rise, construction projects, and restoration efforts. Coupled hydrodynamic and sediment transport models used for this purpose typically are calibrated to water level, currents, and/or suspended-sediment concentratio
Authors
N. K. Ganju, D. H. Schoellhamer
Mercury concentrations and loads in a large river system tributary to San Francisco Bay, California, USA
In order to estimate total mercury (HgT) loads entering San Francisco Bay, USA, via the Sacramento-San Joaquin River system, unfiltered water samples were collected between January 2002 and January 2006 during high flow events and analyzed for HgT. Unfiltered HgT concentrations ranged from 3.2 to 75 ng/L and showed a strong correlation (r2 = 0.8, p < 0.001, n = 78) to suspended sediment concentrat
Authors
N. David, L.J. McKee, F.J. Black, A.R. Flegal, C.H. Conaway, D. H. Schoellhamer, N. K. Ganju
Dietary flexibility in three representative waterbirds across salinity and depth gradients in salt ponds of San Francisco Bay
Salt evaporation ponds have existed in San Francisco Bay, California, for more than a century. In the past decade, most of the salt ponds have been retired from production and purchased for resource conservation with a focus on tidal marsh restoration. However, large numbers of waterbirds are found in salt ponds, especially during migration and wintering periods. The value of these hypersaline wet
Authors
John Y. Takekawa, A.K. Miles, D. C. Tsao-Melcer, D. H. Schoellhamer, S. Fregien, N.D. Athearn
Quantifying fluxes and characterizing compositional changes of dissolved organic matter in aquatic systems in situ using combined acoustic and optical measurements
Studying the dynamics and geochemical behavior of dissolved and particulate organic material is difficult because concentration and composition may rapidly change in response to aperiodic as well as periodic physical and biological forcing. Here we describe a method useful for quantifying fluxes and analyzing dissolved organic matter (DOM) dynamics. The method uses coupled optical and acoustic mea
Authors
B.D. Downing, E. Boss, B.A. Bergamaschi, J.A. Fleck, M. A. Lionberger, N. K. Ganju, D. H. Schoellhamer, R. Fujii
Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007
Initial restoration of former salt evaporation ponds under the South Bay Salt Pond Restoration Project in San Francisco Bay included the changing of water-flow patterns and the monitoring of water quality of discharge waters from the ponds. Low dissolved oxygen (DO) concentrations became evident in discharge waters when the ponds first were opened in 2004. This was a concern, because of the potent
Authors
Gregory Shellenbarger, David H. Schoellhamer, Tara L. Morgan, John Y. Takekawa, Nicole D. Athearn, Kathleen D. Henderson
Water quality
Sustainable water policy in California will require maintaining or improving water quality. The Delta is an important source of drinking water for Californians, but sustaining a quality sufficient for human and agricultural consumption presents a number of problems and challenges to water managers. Similarly, poor environmental water quality is recognized as one of the influential stressors contri
Authors
Samuel N. Luoma, Susan Anderson, Brian A. Bergamaschi, Lisa Holm, Cathy Ruhl, David H. Schoellhamer, Robin Stewart
Science and Products
Filter Total Items: 151
Projected evolution of California's San Francisco bay-delta-river system in a century of climate change
Background: Accumulating evidence shows that the planet is warming as a response to human emissions of greenhouse gases. Strategies of adaptation to climate change will require quantitative projections of how altered regional patterns of temperature, precipitation and sea level could cascade to provoke local impacts such as modified water supplies, increasing risks of coastal flooding, and growing
Authors
James E. Cloern, Noah Knowles, Larry R. Brown, Daniel R. Cayan, Michael D. Dettinger, Tara L. Morgan, David H. Schoellhamer, Mark T. Stacey, Mick Van der Wegen, R.W. Wagner, Alan D. Jassby
Continuous salinity and temperature data from San Francisco estuary, 1982-2002: Trends and the salinity-freshwater inflow relationship
The U.S. Geological Survey and other federal and state agencies have been collecting continuous temperature and salinity data, two critical estuarine habitat variables, throughout San Francisco estuary for over two decades. Although this dynamic, highly variable system has been well studied, many questions remain relating to the effects of freshwater inflow and other physical and biological linkag
Authors
Gregory Shellenbarger, David H. Schoellhamer
Measuring sediment accretion in early tidal marsh restoration
Sediment accretion is a critical indicator of initial progress in tidal marsh restoration. However, it is often difficult to measure early deposition rates, because the bottom surface is usually obscured under turbid, tidally-influenced waters. To accurately measure early sediment deposition in marshes, we developed an echosounder system consisting of a specialized acoustic profiler, differential
Authors
John Y. Takekawa, Isa Woo, Nicole D. Athearn, Scott A. Demers, Rachel J. Gardiner, William M. Perry, Neil K. Ganju, Gregory Shellenbarger, David H. Schoellhamer
Decadal-timescale estuarine geomorphic change under future scenarios of climate and sediment supply
Future estuarine geomorphic change, in response to climate change, sea-level rise, and watershed sediment supply, may govern ecological function, navigation, and water quality. We estimated geomorphic changes in Suisun Bay, CA, under four scenarios using a tidal-timescale hydrodynamic/sediment transport model. Computational expense and data needs were reduced using the morphological hydrograph con
Authors
N. K. Ganju, D. H. Schoellhamer
A Tidally Averaged Sediment-Transport Model for San Francisco Bay, California
A tidally averaged sediment-transport model of San Francisco Bay was incorporated into a tidally averaged salinity box model previously developed and calibrated using salinity, a conservative tracer (Uncles and Peterson, 1995; Knowles, 1996). The Bay is represented in the model by 50 segments composed of two layers: one representing the channel (>5-meter depth) and the other the shallows (0- to 5-
Authors
Megan A. Lionberger, David H. Schoellhamer
Hindcasting of decadal‐timescale estuarine bathymetric change with a tidal‐timescale model
Hindcasting decadal-timescale bathymetric change in estuaries is prone to error due to limited data for initial conditions, boundary forcing, and calibration; computational limitations further hinder efforts. We developed and calibrated a tidal-timescale model to bathymetric change in Suisun Bay, California, over the 1867–1887 period. A general, multiple-timescale calibration ensured robustness ov
Authors
Neil K. Ganju, David H. Schoellhamer, Bruce E. Jaffe
Calibration of an estuarine sediment transport model to sediment fluxes as an intermediate step for simulation of geomorphic evolution
Modeling geomorphic evolution in estuaries is necessary to model the fate of legacy contaminants in the bed sediment and the effect of climate change, watershed alterations, sea level rise, construction projects, and restoration efforts. Coupled hydrodynamic and sediment transport models used for this purpose typically are calibrated to water level, currents, and/or suspended-sediment concentratio
Authors
N. K. Ganju, D. H. Schoellhamer
Mercury concentrations and loads in a large river system tributary to San Francisco Bay, California, USA
In order to estimate total mercury (HgT) loads entering San Francisco Bay, USA, via the Sacramento-San Joaquin River system, unfiltered water samples were collected between January 2002 and January 2006 during high flow events and analyzed for HgT. Unfiltered HgT concentrations ranged from 3.2 to 75 ng/L and showed a strong correlation (r2 = 0.8, p < 0.001, n = 78) to suspended sediment concentrat
Authors
N. David, L.J. McKee, F.J. Black, A.R. Flegal, C.H. Conaway, D. H. Schoellhamer, N. K. Ganju
Dietary flexibility in three representative waterbirds across salinity and depth gradients in salt ponds of San Francisco Bay
Salt evaporation ponds have existed in San Francisco Bay, California, for more than a century. In the past decade, most of the salt ponds have been retired from production and purchased for resource conservation with a focus on tidal marsh restoration. However, large numbers of waterbirds are found in salt ponds, especially during migration and wintering periods. The value of these hypersaline wet
Authors
John Y. Takekawa, A.K. Miles, D. C. Tsao-Melcer, D. H. Schoellhamer, S. Fregien, N.D. Athearn
Quantifying fluxes and characterizing compositional changes of dissolved organic matter in aquatic systems in situ using combined acoustic and optical measurements
Studying the dynamics and geochemical behavior of dissolved and particulate organic material is difficult because concentration and composition may rapidly change in response to aperiodic as well as periodic physical and biological forcing. Here we describe a method useful for quantifying fluxes and analyzing dissolved organic matter (DOM) dynamics. The method uses coupled optical and acoustic mea
Authors
B.D. Downing, E. Boss, B.A. Bergamaschi, J.A. Fleck, M. A. Lionberger, N. K. Ganju, D. H. Schoellhamer, R. Fujii
Dissolved Oxygen in Guadalupe Slough and Pond A3W, South San Francisco Bay, California, August and September 2007
Initial restoration of former salt evaporation ponds under the South Bay Salt Pond Restoration Project in San Francisco Bay included the changing of water-flow patterns and the monitoring of water quality of discharge waters from the ponds. Low dissolved oxygen (DO) concentrations became evident in discharge waters when the ponds first were opened in 2004. This was a concern, because of the potent
Authors
Gregory Shellenbarger, David H. Schoellhamer, Tara L. Morgan, John Y. Takekawa, Nicole D. Athearn, Kathleen D. Henderson
Water quality
Sustainable water policy in California will require maintaining or improving water quality. The Delta is an important source of drinking water for Californians, but sustaining a quality sufficient for human and agricultural consumption presents a number of problems and challenges to water managers. Similarly, poor environmental water quality is recognized as one of the influential stressors contri
Authors
Samuel N. Luoma, Susan Anderson, Brian A. Bergamaschi, Lisa Holm, Cathy Ruhl, David H. Schoellhamer, Robin Stewart