Storm flow dynamics and loads of fecal bacteria associated with ponds in southern piedmont and coastal plain watersheds with animal agriculture

Authors: Jenkins, Michael; ADAMS, M - University Of Georgia; Endale, Dinku; Fisher, Dwight; Lowrance, Robert; NEWTON, G - University Of Georgia

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2014
Publication Date: 1/31/2015
Publication URL: http://handle.nal.usda.gov/10113/60065
Citation: Jenkins, M., Adams, M.P., Endale, D.M., Fisher, D.S., Lowrance, R.R., Newton, G.L. 2015. Storm flow dynamics and loads of fecal bacteria associated with ponds in southern piedmont and coastal plain watersheds with animal agriculture. Agricultural Water Management. 148:97-105.

Interpretive Summary: Animal agriculture in watersheds can be a source of manure bacteria that can contaminate surface waters and put public health at risk. Because of the expanding urban-agriculture interface, preventing surface water contamination with manure pathogens such as Salmonella and pathogenic E. coli is important for sustaining surface water quality. USDA-ARS scientists at the J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA, in collaboration with scientists at the USDA-ARS Southeast Watershed Research laboratory, Tifton, GA, and the University of Georgia, Tifton, GA focused on stream impoundments or ponds as a mechanism of exposing manure pathogens to natural disinfection processes such as solar radiation, and being consumed by predatory protozoa. The scientists examined three ponds in agricultural watersheds, one in the Southern Piedmont, and two in the Coastal Plain of Georgia. Concentrations of fecal indicator bacteria, E. coli and fecal enterococci, and pathogenic Salmonella and E. coli were determined for pond inflow and outflow under rainstorm conditions. Transit through the pond in the Southern Piedmont effectively decreased the concentrations of fecal bacteria; the ponds in the Coastal Plain, however, did not. Unlike the pond in the Southern Piedmont, the in- and outflow at the two ponds in the Coastal Plain was characteristically ephemeral. These results indicated that impoundments in watersheds containing animal agriculture with continuous in- and outflow can improve downstream water quality under storm flow conditions.

Technical Abstract: Storm events that increase hydrologic flow rates can disturb sediments and produce overland runoff in watersheds with animal agriculture, and, thus, can increase surface water concentrations of fecal bacteria and risk to public health. We tested the hypothesis that strategically placed ponds in watersheds with animal agriculture would attenuate downstream fluxes of fecal bacteria. We measured concentrations and fluxes of fecal indicator bacteria (commensal Escherichia coli and fecal enterococci) and manure pathogens (Salmonella and E. coli 0157:H7) in in- and outflows of Bishop Pond in the Piedmont of Georgia during three storm events and in- and outflow concentrations and fluxes of fecal indicator bacteria at Ponds A and C in the Coastal Plain of Georgia during two storm events. Mean concentrations and fluxes of fecal indicator bacteria associated with pond in- and outflow hydrographic storm flow types at Bishop Pond were significantly greater than their mean base flow concentrations and fluxes. Transiting Bishop Pond under storm flow conditions significantly reduced the outflow concentrations and fluxes of fecal indicator bacteria compared to corresponding inflow measurements. Unlike fecal indicator bacteria, transit through Bishop Pond appeared not to reduce outflow concentrations and fluxes of Salmonella or E. coli 0157:H7. At Ponds A and C in the Coastal Plain in- and outflow concentrations of the fecal indicator bacteria associated with the hydrographic rise of the storms were greater than mean base flow concentrations. In contrast to Bishop Pond storm in- and outflow concentrations and fluxes, the fecal indicator bacteria at Ponds A and C were not different. Whereas Bishop Pond attenuated downstream fluxes of fecal bacteria, Ponds A and C, with characteristic ephemeral in- and outflow under base flow conditions were not effective at reducing downstream fluxes of fecal bacteria under storm flow conditions.