Levels and patterns of fecal indicator bacteria in stormwater runoff from homogenous land use sites and urban watersheds

Abstract

Routine stormwater monitoring programs focus on quantification of average fecal indicator bacteria (FIB) concentration at the terminal watershed discharge point. While important for permit compliance, such monitoring provides little insight into relative bacteria levels from different land use types or the mechanisms that influence FIB concentrations. The goal of this study was to quantify the relative levels and flux patterns of Escherichia coli, enterococci, and total coliforms from representative land use (LU) types. Bacteria concentrations were measured over the entire storm duration from 8 different LU types over 13 storm events in 5 southern California watersheds during the 2000-2005 storm seasons. In addition, runoff samples were collected from 8 bottom of the watershed mass emission (ME) sites. Intra-storm and intra-season patterns were investigated in order to identify mechanisms that influence patterns of FIB concentrations.Mean FIB event mean concentrations (EMCs) at LU sites ranged from 10 3 to 10 5 MPN/100 ml.Recreational (horse stables) LU sites contributed significantly higher storm EMCs than other LU types. Early season storms repeatedly produced higher EMCs than comparably sized late season storms. For most storms sampled, the highest bacterial concentrations occurred during the early phases of stormwater runoff with peak concentrations usually preceding peak flow.

Effect of land use and hydrological processes on Escherichia coli concentrations in streams of tropical, humid headwater catchments

“…In urban areas without adequate wastewater treatment or stormflow mitigation management, heavy rainfall washes off FIB and other contaminants from the ground surface12. In rural areas, especially in areas with bare soil and/or annual crops, similar heavy rainfall leads to the erosion of soil and, hence of any faecal matter on the soil surface313.…”

Instream Bacteria Influences from Bird Habitation of Bridges

“…In evaluating bacteria concentrations in stormwater runoff, Tiefenthaler et al . () found patterns within storms with the highest bacterial concentrations often preceding peak flow, while Edwards et al . () noted peaks in FIB following peak flow.…”

“…When stormwater runoff is considered, the relationship of flow with bacteria concentrations becomes more complicated and depends greatly on land cover and land use characteristics and the timing and intensity of stormwater contributions. In evaluating bacteria concentrations in stormwater runoff, Tiefenthaler et al (2011) found patterns within storms with the highest bacterial concentrations often preceding peak flow, while Edwards et al (1997) noted peaks in FIB following peak flow. Depending on the watershed, contributions associated with stormwater runoff may potentially mask contributions from birded bridges, so sources associated with ambient and stormwater flows may need to be considered separately in impaired watersheds.…”

Use of a Volunteer Monitoring Program to Assess Water Quality in a TMDL Watershed Utilized for Recreational Use, Pickens County, South Carolina

“…Research suggests that in some watersheds which are impaired due to high bacteria, indicator bacteria levels increase with increasing flow rate, usually immediately after significant rainfall events (Tiefenthaler et al, 2011;Marsalek and Rochfort, 2004). Ironically, it is under increased flow conditions after rainfall events that Twelve Mile Creek experiences its highest use by paddlers (AWA, 2014).…”