ARS | Publication request: Microbial water quality in streams as affected by high flow events

Submitted to: European Geosciences Union General Assembly Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: January 28, 2011
Publication Date: April 4, 2011
Citation: Guber, A.K., Pachepsky, Y.A., Shelton, D.R. 2011. Microbial water quality in streams as affected by high flow events. [abstract] European Geosciences Union General Assembly Proceedings. 13.(2011-117).

Technical Abstract: Bottom sediments in surface water sources were shown to serve as reservoirs of pathogen and indicator microorganisms. Resuspension of these sediments during the high flow events strongly modifies microbial quality of recreation and irrigation waters. Therefore, changes in microbial water quality are expected due to climatic changes that affect the precipitation frequency-duration-intensity relationships. The objective of this work was to summarize results of three years of artificial high flow experiments at the perennial first-order creek in riparian zone. The artificial high flow events were created at the USDA-ARS OPE3 research site by releasing 80T of tap water with tracers in four allotments during 20 min and monitoring streamflow, and E. coli and tracer concentrations at four stations with automated refrigerated samplers along the 630 m stream reach. Sediment texture and E. coli concentrations were measured before the event and on the next day. The E. coli concentration in stream water during and after the event far exceeded the limits recommended for recreation and irrigation waters. Based on bacteria mass balance, E. coli were released on average from the top 5 mm of the sediment layer. E. coli concentrations in sediments were one order of magnitude larger days after the experiment than before the event. Semivariograms of E. coli concentrations before events were periodic indicative to the extreme patchiness, whereas no spatial structure was found in E. coli concentrations day after the event. Tracer breakthrough concentrations suggested a slow return of bacteria from stagnant zones near stream banks to the flow zone in the creek. On one of the years, A high concentration of streambed E. coli (‘‘hotspot”) resuspended within the first reach caused a pulse of high E. coli concentrations that propagated along the creek without substantial attenuation. Functioning of environmental reservoirs of E. coli such as bottom sediment, bank soils, periphyton, and algae will change as the climate changes, and this change needs to be understood to foresee the changes in microbial quality of irrigation and recreation waters.