To develop effective groundwater pollution control strategies for the Kathmandu Valley, Nepal, seasonal variations in microbial quality and their underlying mechanisms must be understood. However, to date, there are no studies that address these topics. In this study, groundwater samples from dug wells were collected during the dry and wet seasons from 2009 to 2012, and Escherichia coli (E. coli) and total coliforms were analysed. Three wells were monitored each month for a year. Microbial concentrations in shallow groundwater were significantly higher during the wet season than during the dry season. Analyses of rainfall and E. coli concentrations in different seasons indicated that a high level of faecal material infiltration during the rainy season may have caused the seasonal variations in microbial quality. A moderate to strong relationship between E. coli concentrations and groundwater level suggested that the rise in groundwater levels during the wet season may be another reason for this variation. This long time-scale survey detected a significant decline in the microbial quality of shallow groundwater during the wet season as compared with the dry season. We propose that the infiltration of contaminants and change in groundwater level are the two probable mechanisms for the observed seasonal differences.
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Research Article|
November 20 2013
Seasonal variation in the microbial quality of shallow groundwater in the Kathmandu Valley, Nepal
Sadhana Shrestha;
Sadhana Shrestha
1Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Kofu 400-8511, Japan
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Takashi Nakamura;
Takashi Nakamura
2International Research Centre for River Basin Environment, University of Yamanashi, Kofu 400-8511, Japan
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Rabin Malla;
Rabin Malla
3Center of Research for Environment Energy and Water, Baluwatar, Kathmandu – 4, Nepal
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Kei Nishida
2International Research Centre for River Basin Environment, University of Yamanashi, Kofu 400-8511, Japan
E-mail: nishida@yamanashi.ac.jp
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Water Supply (2014) 14 (3): 390–397.
Article history
Received:
July 30 2013
Accepted:
November 06 2013
Citation
Sadhana Shrestha, Takashi Nakamura, Rabin Malla, Kei Nishida; Seasonal variation in the microbial quality of shallow groundwater in the Kathmandu Valley, Nepal. Water Supply 1 June 2014; 14 (3): 390–397. doi: https://doi.org/10.2166/ws.2013.213
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Sadhana Shrestha, Takashi Nakamura, Rabin Malla, Kei Nishida; Seasonal variation in the microbial quality of shallow groundwater in the Kathmandu Valley, Nepal. Water Supply 1 June 2014; 14 (3): 390–397. doi: https://doi.org/10.2166/ws.2013.213
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