Water Resources Professional Project Reports

Document Type

Report

Publication Date

Summer 2022

Abstract

With Escherichia coli (E. coli) being a widely used indicator of pathogen contamination, concentrations need to be fully understood to create effective best management practices for water quality managers. While management and impairment standards are focused on concentrations in the water column, there is research showing that E. coli attaches to sediment in the river and acts as a reservoir for E. coli. The Middle Rio Grande in the South Valley, New Mexico is classified as an impaired reach because it exceeds the E. coli water quality standard. Exceedances are commonly seen during the wet season in high flows, but exceedances were reported year-round in this section of the Rio Grande. This research seeks to improve the understanding of the E. coli concentrations in bed sediment through this impaired reach of the Middle Rio Grande during the dry season (November 30 through June). Therefore, E. coli, bed particle size, suspended sediment, and water quality parameters were collected during the dry season of 2020 and 2021. To understand the source of E. coli, microbial source tracking marker (MST) samples from the water column and bed sediment were also collected. This study detected E. coli in the bed sediment in 94 percent of the samples (n=72). The mean E. coli concentrations in bed sediment ranged from 0.54 to 10.22 most probable number per gram dry weight. Spatial differences of E. coli in bed sediment were observed along the longitudinal transect. In the 72 bed sediment samples collected, the human marker was detected in 35 samples, the canine marker was detected in 11 samples, and the avian marker was detected in 13 samples. While no strong or statistically significant correlations between E. coli and MST marker concentrations with water quality parameters were observed, a known baseline concentration of E. coli in the bed sediment is valuable for water managers tasked with improving water quality.

Language (ISO)

English

Keywords

Escherichia coli, E. coli, water, Rio Grande

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