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A preliminary investigation of temporal and spatial variations in floodwater chemistry was conducted during winter and spring 1998 in the Yolo Bypass floodplain of the Sacramento River system. Samples were collected at locations along the eastern margin of the floodplain over the duration of the study and across the floodplain during major periods of inundation. Specific conductance and dissolved organic carbon concentrations along the eastern margin of the Yolo Bypass varied inversely with discharge. The Sacramento River was the greatest source of discharge to the floodplain during major periods of inundation. Increases in specific conductance and dissolved organic carbon were observed along the eastern margin...
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Partitioning of zinc (Zn) between dissolved and colloidal phases was studied in the upper Animas River. Most of the Zn was dissolved in the water column, but a variable fraction of the total Zn was associated with aluminum (Al)- and iron (Fe)-rich colloidal particles. Colloids were supplied to the river by tributary creeks that drain areas with natural sulfide mineral deposits and debris from abandoned mines. The fraction of the total Zn that was in the colloidal phase increased with pH in the river, indicating the possibility of adsorption by colloidal Al and Fe. The influence of pH was confirmed in laboratory experiments in which larger fractions of the total Zn were associated with the colloids when pH was increased...
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The acidic discharge from Cement Creek, containing elevated concentrations of dissolved metals and sulphate, mixed with the circumneutral-pH Animas River over a several hundred metre reach (mixing zone) near Silverton, CO, during this study. Differences in concentrations of Ca, Mg, Si, Sr, and SO42− between the creek and the river were sufficiently large for these analytes to be used as natural tracers in the mixing zone. In addition, a sodium chloride (NaCl) tracer was injected into Cement Creek, which provided a Cl− ‘reference’ tracer in the mixing zone. Conservative transport of the dissolved metals and sulphate through the mixing zone was verified by mass balances and by linear mixing plots relative to the injected...
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Acidic waters from Cement Creek discharge into the circum-neutral Animas River in a high-elevation region of the San Juan Mountains near Silverton, Colorado. Cement Creek is acidic and enriched in metals and sulfate because it is fed by discharges from abandoned mines and natural mineral deposits. Mixing with the Animas River raises the pH and produces precipitates of iron and aluminum (oxy)hydroxides, which in turn can adsorb other metals. This confluence was studied in 1996 and 1997 to better understand mixing and sorption processes which are common during the neutralization of acidic streams. The photographs in this report show flow braiding and other features that influenced the way the two streams mixed during...
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Salinity and temperature were measured in near-surface waters at Dumbarton Bridge in South San Francisco Bay during the 1999?2002 water years (1999WY?2002WY). The complete data set from this site, which included 1990WY?1993WY and 1995WY?1998WY, provided a time?series of observations covering a wide range of hydrologic conditions. These conditions included critically dry years and years with above-normal and near?record precipitation and discharges from the major rivers and local streams. Data collection at 15?minute intervals allowed resolution of variability associated with daily tides and other short-term phenomena. Both local stream discharges to South San Francisco Bay and Sacramento?San Joaquin River discharges...
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