HR: 0800h
AN: H41C-0649    [Abstracts]
TI: Lagrangian water quality dynamics in the San Luis Drain, California.
AU: * Volkmar, E C
EM: ecvolkmar@ucdavis.edu
AF: University of California, Davis, Department of Land, Air and Water Resources, One Shields Avenue, Davis, CA 95616,
AU: Dahlgren, R A
EM: radahlgren @ucdavis.edu
AF: University of California, Davis, Department of Land, Air and Water Resources, One Shields Avenue, Davis, CA 95616,
AU: Stringfellow, W T
EM: wstringfellow@lbl.gov
AF: Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720,
AU: Henson, S S
EM: sshenson@gmail.com
AF: University of California, Davis, Department of Land, Air and Water Resources, One Shields Avenue, Davis, CA 95616,
AU: Borglin, S E
EM: seborglin@lbl.gov
AF: Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720,
AU: Kendall, C
EM: ckendall@usgs.gov
AF: United States Geological Survey, Water Resources Division, 345 Middlefield Rd, Menlo Park, CA 94025,
AB: Integration of temporal changes in biological and water quality constituents during downstream transport is critical to understanding aquatic ecosystem and biogeochemical dynamics of rivers, estuaries, and the near- coastal waters into which rivers flow. Changes in chemical, physical, and biological water quality constituents during downstream transport can be evaluated by following a specific parcel of water, known as a Lagrangian study. The objective of this study was to differentiate changes in water quality constituents occurring within a parcel of water as it travels downstream to the changes observed at a fixed sampling location. We sampled a parcel of agricultural drainage water as it traveled downstream for 84 h in a concrete-lined channel (San Luis Drain in San Joaquin Valley) with no additional water inputs or outputs. The Lagrangian sampling occurred in August 2006 and June 2007. Data from the Lagrangian study was compared to data collected at a fixed point using an automatic pump sampler and water quality sonde. Fluorescence (a measure of algal pigments), dissolved oxygen, temperature, pH, and conductivity were measured every 30 minutes, as well as collecting grab samples every 2 h for nutrient and suspended sediment analyses. Sinusoidal diel (24 h) patterns were observed for dissolved oxygen, pH, and temperature within the parcel of water. Algal pigments, nutrients, suspended solids, and turbidity did not exhibit sinusoidal diel patterns, generally observed at a fixed sampling location. The diel patterns observed indicated changes that would occur during downstream transport. Algal pigments showed a rapid day time increase during the first 24 to 48 h followed by a plateau or decrease for the remainder of the study. Algal growth was apparent each day during the study, as measured by increasing dissolved oxygen concentrations, in spite of non-detectable phosphate concentrations (<5 ppb) and nearly complete consumption of soluble silica during the 2007 study. Because current monitoring programs generally entail weekly to monthly (usually midday) sampling, they are insufficient to accurately estimate fluxes of nutrients and organic matter through productive rivers, such as the San Joaquin. Information from this study will assist in developing appropriate monitoring protocols to capture diel variability and also provides process-level information for understanding changes in water quality constituents during downstream transport.
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0496 Water quality
DE: 1852 Plant uptake
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2007 Fall Meeting