Biogeochemistry of a California Floodplain Revealed by High Resolution Temporal Sampling
Abstract
Previous weekly monitoring of a floodplain in the California Central Valley confirmed the dynamic spatiotemporal nature of biogeochemical floodplain processes, but did not resolve short-term (<1 day) temporal dynamics. This study examined water quality on a fine temporal scale during and after flooding to elucidate short-term variations in biogeochemical processes. In February-March 2004, we collected water samples using autosamplers at the entrance and exit of the floodplain. We detected diel patterns in chlorophyll-a, with concentrations fluctuating 50% - 200% over 12 hours. Nitrate (NO3--N), ammonium (NH4+-N) and orthophosphate (PO43--P) concentrations were highest during flooding (0.68 ppm, 0.35 ppm and 101 ppb, respectively). NO3--N and PO43--P decreased 0.12 ppm and 4 ppb per day during draining and remained constant during ponding; while NH4+-N remained constant during draining and increased 0.02 ppm per day during ponding. Total suspended solids (TSS) were 25% - 65% greater at the entrance than exit; fluctuated daily with the river hydrograph and decreased while volatile suspended solids increased 9% of TSS per day as hydrologic residence time increased. Our data demonstrate dramatic floodplain water quality changes occurring over a few hours that depend on connectivity phase and hydrologic residence time.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2005
- Bibcode:
- 2005AGUSMNB13B..06G
- Keywords:
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- 1806 Chemistry of fresh water;
- 1821 Floods;
- 1871 Surface water quality;
- 1890 Wetlands;
- 9901 NABS Student Award - Basic Research