Temporal variations of Escherichia coli concentrations in a large Midwestern river

Journal of Hydrology
By: , and 



The Raccoon River used by the Des Moines Water Works to serve more than 400,000 people in central Iowa is threatened by contamination from Escherichia coli bacteria from point and nonpoint sources. The 9389 km2 watershed is highly agricultural, with 73% of the land in row crop production and widespread animal production. Results from 2155 grab samples from 1997 to 2005 for E. coli analysis were examined for temporal variations. E. coli concentrations were found to vary across years, seasons, and flow conditions, with a 9-year mean value of 1156 most probable number (MPN)/100 ml. Monthly concentrations exhibited clear seasonality with highest values in May through July. Although E. coli concentrations were higher during periods of greater discharge, the relation of log E. coli to log discharge was not particularly strong (r2 = 0.35). The variogram of E. coli concentrations showed temporal correlation within a span of 4 days suggesting that concentrations measured on 1 day may be related in time to concentrations measured up to 3 days later and beyond 4 days the concentrations vary randomly. The spectral analysis of the time series of E. coli was also carried out and was fitted well with the spectrum of an exponential covariance function. Deciphering temporal patterns and correlation of E. coli bacteria in streams may be useful for developing future monitoring strategies to track concentration patterns and loads. ?? 2008 Elsevier B.V. All rights reserved.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Temporal variations of Escherichia coli concentrations in a large Midwestern river
Series title Journal of Hydrology
DOI 10.1016/j.jhydrol.2008.11.029
Volume 365
Issue 1-2
Year Published 2009
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Hydrology
First page 79
Last page 85