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

Abstract

Lack of access to clean water and adequate sanitation continues to be a major brake on development. Here we present the results of a 12-month investigation into the dynamics of Escherichia coli, a commonly used indicator of faecal contamination in water supplies, in three small, rural catchments in Laos, Thailand and Vietnam. We show that land use and hydrology are major controlling factors of E. coli concentrations in streamwater and that the relative importance of these two factors varies between the dry and wet seasons. In all three catchments, the highest concentrations were observed during the wet season when storm events and overland flow were highest. However, smaller peaks of E. coli concentration were also observed during the dry season. These latter correspond to periods of intense farming activities and small, episodic rain events. Furthermore, vegetation type, through land use and soil surface crusting, combined with mammalian presence play an important role in determining E. coli loads in the streams. Finally, sampling during stormflow revealed the importance of having appropriate sampling protocols if information on maximum contamination levels is required as grab sampling at a fixed time step may miss important peaks in E. coli numbers.

Hydrological Regime and Water Shortage as Drivers of the Seasonal Incidence of Diarrheal Diseases in a Tropical Montane Environment

“…More detail about the Nam Khan and the nested Houay Xon and Houay Pano catchments, including the land use and livestock units, have been presented in previous studies [61,63,64,66]. River monitoring and sampling allows recording discharge and water quality data integrating the catchment-scale spatial heterogeneity of rainfall, soil and land use upstream the monitoring stations [65].…”

“…from subsistence shifting agriculture to cash crops and tree plantations) have increased soil crusting, runoff, soil erosion and in-stream suspended sediment loads [58–60]. Floods and the consequent erosion drive FIB dissemination in surface water in Laos [61–64]. To our knowledge, few studies have yet applied mixed methods approaches to assess diarrheal disease risk factors [45], and no studies have given an estimate of diarrhea incidences, together with water quality factors such as river discharge, suspended sediment and FIB loads, along with the commonly assessed climate factors such as temperature and rainfall, and with sociological factors such as hygiene practices.…”

Microbial Water Quality: Monitoring and Modeling

“…Surface properties of the porous media can exert strong control on microbial transport if straining is not a leading process. Irreversible attachment was the dominant mechanism of virus retention during transport through saturated sand‐packed columns in the work of Sasidharan et al (2018). The fractions of two viruses under study that still could pass the columns were affected by temperature.…”

Hydrological modeling of Fecal Indicator Bacteria in a tropical mountain catchment

“…This has resulted in high levels of fecal contamination in surface waters Causse et al, 2015;Ribolzi et al, 2016;Rochelle-Newall et al, 2016). Steep slopes and high runoff, soil erosion and subsequent soil particle transfer to river networks exacerbates the microbial contamination of rivers (Patin et al, 2012;Ziegler et al, 2009).…”