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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.


Related in: MedlinePlus

The three studied catchments of the MSEC network and their land use in 2015.The land use maps were created with land survey data from the three sites using QGIS software (http://www.qgis.org/en/site/) and the map of Southeast Asia was created for this article with Microsoft Office Visio 2007.
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f1: The three studied catchments of the MSEC network and their land use in 2015.The land use maps were created with land survey data from the three sites using QGIS software (http://www.qgis.org/en/site/) and the map of Southeast Asia was created for this article with Microsoft Office Visio 2007.

Mentions: The three study sites (Fig. 1) are subject to a tropical climate which is influenced by the southwest monsoon bringing warm and humid air masses during the wet season (April-September), and by the northeast monsoon bringing colder, dryer air during the dry season (October-March). Rainfall is highly seasonal with more than 80% of annual rainfall occurring during the wet season. In Laos and Thailand average daily temperatures are highest in April at the end of the dry season when they can reach 40 °C. In Vietnam the highest temperatures generally occur in July and August. Vietnam also has the highest amplitude in terms of temperature variations over the annual cycle (+/−23 °C relative to +/−16 and 15 °C for Laos and Thailand, respectively). Global radiation (GR) varies between 401 and 2,151 J cm−2 and GR is the highest in Laos, the lowest in Vietnam and intermediate in Thailand (Table 1).


Effect of land use and hydrological processes on Escherichia coli concentrations in streams of tropical, humid headwater catchments
The three studied catchments of the MSEC network and their land use in 2015.The land use maps were created with land survey data from the three sites using QGIS software (http://www.qgis.org/en/site/) and the map of Southeast Asia was created for this article with Microsoft Office Visio 2007.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: The three studied catchments of the MSEC network and their land use in 2015.The land use maps were created with land survey data from the three sites using QGIS software (http://www.qgis.org/en/site/) and the map of Southeast Asia was created for this article with Microsoft Office Visio 2007.
Mentions: The three study sites (Fig. 1) are subject to a tropical climate which is influenced by the southwest monsoon bringing warm and humid air masses during the wet season (April-September), and by the northeast monsoon bringing colder, dryer air during the dry season (October-March). Rainfall is highly seasonal with more than 80% of annual rainfall occurring during the wet season. In Laos and Thailand average daily temperatures are highest in April at the end of the dry season when they can reach 40 °C. In Vietnam the highest temperatures generally occur in July and August. Vietnam also has the highest amplitude in terms of temperature variations over the annual cycle (+/−23 °C relative to +/−16 and 15 °C for Laos and Thailand, respectively). Global radiation (GR) varies between 401 and 2,151 J cm−2 and GR is the highest in Laos, the lowest in Vietnam and intermediate in Thailand (Table 1).

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.


Related in: MedlinePlus