Evaluation of land use and water quality in an agricultural watershed in the USA indicates multiple sources of bacterial impairment

Abstract

Pathogens are the number one cause of impairments of assessed rivers and streams in the USA and pose a significant human health hazard. The Dry Run Creek Watershed in Northeast Iowa has been designated as impaired by the State of Iowa because of high levels of Escherichia coli bacteria. To investigate the nature of this impairment, land use and stream bank assessments were coupled with comprehensive water quality monitoring. Physical, chemical, and biological parameters were measured at 13 different sites in the watershed, including pH, temperature, conductivity, dissolved oxygen, turbidity, total Kjeldahl nitrogen, ammonia-N, nitrate + nitrite-N, total phosphorus, and E. coli. In addition, benthic macroinvertebrate communities were analyzed at seven sites, and optical brightener tests were performed late in the season. Results identified segments of the watershed that were more prominent contributors of E. coli, and correlations were observed between levels of E. coli and several chemical parameters, including ammonia-N, total Kjeldahl nitrogen, and total phosphorus. Interestingly, distinct sites emerged as more prominent contributors of these elements during rain vs. non-rain events, suggesting different types of sources. Both the amount of rainfall and the time elapsed between the rain event and the sampling influenced E. coli levels during wet weather conditions. Nitrate + nitrite-N displayed a unique response to rain events compared with the other parameters, suggesting a different delivery route. Analyses of benthic macroinvertebrate communities were consistent with pollution trends. Collectively, these data suggest distinct agriculturally related E. coli contributions, as well as specific areas and practices for water quality improvement strategies. This study can serve as a resource for evaluating agricultural watersheds that are impaired for bacteria.

Microbiological quality of lettuce (Lactuca sativa) irrigated with wastewater in Addis Ababa, Ethiopia and effect of green salads washing methods

“…Thus, grey and black waters originated from households appear to be the key source of faecal contamination. This is consistent with the studies by Fischer et al (Fisher et al 2000), Monaghan et al (2009), Wittman et al (2013) and Schreiber et al (2015) who demonstrated the considerable impact of anthropogenic inputs on microbial quality of river water. As reflected by water quality, also the lettuce samples from all farming sites had high faecal coliform levels exceeding recommended thresholds, similar to the findings in other sub-Saharan cities (Keraita et al 2002;Srikanth and Naik 2004;Amoah et al 2005Amoah et al , 2007a.…”

Long-term characterization of residential runoff and assessing potential surrogates of fecal indicator organisms

“…A simple linear regression demonstrated a significant, albeit very weak, w a t e r r e s e a r c h 7 4 ( 2 0 1 5 ) 6 7 e7 6 relationship to EC (R 2 ¼ 0.08, P < 0.0001, data not shown); furthermore, previous studies have also demonstrated at least some relationship to EC. Total nitrogen has demonstrated a positive correlation to EC in urban stormwater (Wittman et al, 2013); however, this relationship can also be negative in other watersheds (Gu et al, 2013). Gagliardi and Karns (2000) attributed this relationship to fecal contamination, which contains high levels of both nitrogen and EC.…”

Trout habitat and stream restoration in Decorah

“…Unmanaged stormwater run-off contributes to the problem of bacterial contamination, the major source of impairment in streams and river in Decorah, as well as high water temperature, inadequate dissolved oxygen and high turbidity that affect trout habitat in Decorah (Wittman et al, 2013).…”