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

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Baseflow (inter-storm) and stormflow in the Dong Cao catchment, Vietnam.Rainfall intensity (daily time step; mm d−1); stream specific discharge (Qs, L s−1 ha−1); electrical conductivity (EC, μS cm−1); total suspended solids (TSS, g L−1); E. coli concentration in the stream (E. coli, MPN 100 mL−1). Black filled symbols: baseflow samples, grey filled symbols: stormflow samples.
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f3: Baseflow (inter-storm) and stormflow in the Dong Cao catchment, Vietnam.Rainfall intensity (daily time step; mm d−1); stream specific discharge (Qs, L s−1 ha−1); electrical conductivity (EC, μS cm−1); total suspended solids (TSS, g L−1); E. coli concentration in the stream (E. coli, MPN 100 mL−1). Black filled symbols: baseflow samples, grey filled symbols: stormflow samples.

Mentions: A similar pattern was observed in Dong Cao, Vietnam (Fig. 3) although rain intensity was higher in Vietnam during the study period, reaching 209 mm d−1 on September 17th, 2015. Total annual rainfall the catchment was 1,474 mm, close to the annual average of 1,556 mm (Table 1). As in Laos, heavy rains resulted in peaks of discharge in the stream and the highest discharge (4.55 L s−1 ha−1) was observed on September 17th, 2015 concomitant with the highest rainfall intensities. EC decreased initially from October 2014 to December 2014 and thereafter remained relatively stable over the year. A similar pattern was observed for TSS. E. coli numbers varied from 78 to 890 MPN 100 mL−1 and were significantly lower (p < 0.05) than those observed in Laos. The highest numbers found during the periods of higher rainfall. Compared to the Houay Pano catchment, the differences in values between baseflow and stormflow in the Dong Cao catchment were lower. For example, EC was about 50 μS cm−1 lower in the stormflow samples, relative to EC during the baseflow period. Moreover, E. coli numbers were only an order of magnitude higher in the stormflow samples whereas TSS was two orders of magnitude higher.


Effect of land use and hydrological processes on Escherichia coli concentrations in streams of tropical, humid headwater catchments
Baseflow (inter-storm) and stormflow in the Dong Cao catchment, Vietnam.Rainfall intensity (daily time step; mm d−1); stream specific discharge (Qs, L s−1 ha−1); electrical conductivity (EC, μS cm−1); total suspended solids (TSS, g L−1); E. coli concentration in the stream (E. coli, MPN 100 mL−1). Black filled symbols: baseflow samples, grey filled symbols: stormflow samples.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015105&req=5

f3: Baseflow (inter-storm) and stormflow in the Dong Cao catchment, Vietnam.Rainfall intensity (daily time step; mm d−1); stream specific discharge (Qs, L s−1 ha−1); electrical conductivity (EC, μS cm−1); total suspended solids (TSS, g L−1); E. coli concentration in the stream (E. coli, MPN 100 mL−1). Black filled symbols: baseflow samples, grey filled symbols: stormflow samples.
Mentions: A similar pattern was observed in Dong Cao, Vietnam (Fig. 3) although rain intensity was higher in Vietnam during the study period, reaching 209 mm d−1 on September 17th, 2015. Total annual rainfall the catchment was 1,474 mm, close to the annual average of 1,556 mm (Table 1). As in Laos, heavy rains resulted in peaks of discharge in the stream and the highest discharge (4.55 L s−1 ha−1) was observed on September 17th, 2015 concomitant with the highest rainfall intensities. EC decreased initially from October 2014 to December 2014 and thereafter remained relatively stable over the year. A similar pattern was observed for TSS. E. coli numbers varied from 78 to 890 MPN 100 mL−1 and were significantly lower (p < 0.05) than those observed in Laos. The highest numbers found during the periods of higher rainfall. Compared to the Houay Pano catchment, the differences in values between baseflow and stormflow in the Dong Cao catchment were lower. For example, EC was about 50 μS cm−1 lower in the stormflow samples, relative to EC during the baseflow period. Moreover, E. coli numbers were only an order of magnitude higher in the stormflow samples whereas TSS was two orders of magnitude higher.

View Article: PubMed Central - PubMed

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.

No MeSH data available.