Publications

@article{Ghimire2023b,
title = {Hydro-chemical characterization and quality assessment of shallow groundwater in parts of the Kathmandu Valley, Nepal},
author = {Manisha Ghimire and Sadhana Pradhanang Kayastha and Tejendra Regmi and Chandrashekhar Bhuiyan},
url = {https://www.sciencedirect.com/science/article/pii/S147470652200242X},
doi = {doi.org/10.1016/j.pce.2022.103349},
issn = {1474-7065},
year = {2023},
date = {2023-02-01},
journal = {Physics and Chemistry of the Earth},
volume = {129},
abstract = {Groundwater is the main source of water for drinking and irrigation in the Kathmandu Valley of Nepal. Although quality of groundwater is crucial for public health, there is little information available. Considering this, groundwater samples were collected during the post-monsoon and winter from 35 dug wells of Lalitpur Metropolitan City located in the Kathmandu Valley. Chemical analysis of these samples has revealed alkaline nature of groundwater. Factor analysis (FA) and correlation analysis (CoA) have identified lithology, geogenic, and anthropogenic activities as the main factors governing groundwater chemistry. Cluster Analysis (CA) segregated samples into five clusters indicating difference in their hydrochemistry. The Weightage Arithmetic Water Quality Index (WAWQI) has revealed unsuitability of groundwater for drinking. Among the chemical constituents, Fe, Ca2+, Mg2+ and PO43− are found most influential. Concentration of iron, and calcium were much higher than the recommended limit for drinking water. High total coliform (TC) content in particular makes groundwater of the valley totally unsafe for drinking. While percentage of sodium (Na%), sodium adsorption ration (SAR), and salinity hazard values of the samples are found suitable, on the basis of the Permeability Index (PI), several winter and post-monsoon samples were unsuitable for irrigation. This study strongly recommends for treatment and purification of groundwater before supply and use for drinking and irrigation purposes to minimise health-risk.},
keywords = {Cluster analysis, Factor analysis, Groundwater contamination, Hydro-geochemistry, Kathmandu Valley},
pubstate = {published},
tppubtype = {article}
}

@article{Shakya2022,
title = {Tap Water Quality Degradation in an Intermittent Water Supply Area},
author = {Bijay Man Shakya and Takashi Nakamura and Sadhana Shrestha and Sarad Pathak and Kei Nishida and Rabin Malla},
url = {https://link.springer.com/article/10.1007/s11270-021-05483-8},
doi = {https://doi.org/10.1007/s11270-021-05483-8},
year = {2022},
date = {2022-02-25},
journal = {Water, Air, & Soil Pollution},
volume = {233},
number = {81},
abstract = {Decentralized tap water systems are an important drinking water source worldwide. A good quality, high-pressure continuous water supply (CWS) is always the target of any urban settlement. However, tap water in some areas are reported with deteriorated water quality even though treated well before supplying. Such deterioration of tap water quality is reported widely from areas with low water availability and in economically poor countries where water are supplied intermittently (IWS). This study focuses in identifying tap water quality in IWS and causes of water quality degradation using nitrate-nitrogen (NO3-N) as an indicator and stable isotopes of hydrogen (δD) as tracer. Nine water reservoirs and ninety municipal tap water (ten per reservoir) samples were collected during the wet (June–September) and dry (November–February) seasons in the Kathmandu Valley (KV), Nepal. Ten percent of the tap water samples exhibited higher NO3-N than those of their respective reservoirs during the wet season, while 16% exhibited higher concentrations during the dry season. Similarly, the isotopic signatures of tap water exhibited 3% and 23% higher concentrations than those of their respective reservoirs during the wet and dry seasons, respectively. Coupling analysis between NO3-N and δD demonstrates close connection of groundwater and tap water. The results indicate groundwater intrusion as the primary component in controlling tap water quality variations within the same distribution networks during IWS. Meanwhile, the obtained results also indicate probable areas of intrusion in the KV as well as usefulness of δD as a tool in the assessment of tap water systems.},
keywords = {Developing country, Groundwater intrusion, Intermittent water supply, Kathmandu Valley, Low pressurized tap, Tap water contamination},
pubstate = {published},
tppubtype = {article}
}

@article{Prajapati2021,
title = {Streams, sewage, and shallow groundwater: stream-aquifer interactions in the Kathmandu Valley, Nepal},
author = {Rajaram Prajapati and Nick N. Overkamp and Niek Moesker and Kate Happee and Rick van Bentem and Anusha Danegulu and Bikesh Manandhar and Nischal Devkota and Amber Bahadur Thapa and Surabhi Upadhyay and Rocky Talchabhadel and Bhesh Raj Thapa and Rabin Malla and Vishnu Prasad Pandey and Jefrey C. Davids},
url = {https://link.springer.com/article/10.1007%2Fs40899-021-00542-8},
doi = {doi.org/10.1007/s40899-021-00542-8},
year = {2021},
date = {2021-08-02},
journal = {Sustainable Water Resources Management},
volume = {7},
number = {5},
pages = {1-18},
abstract = {The Kathmandu Valley in Nepal is facing a water quantity and quality crisis due to rapid urbanization and haphazard water and wastewater planning and management. Annually, groundwater extractions in the Kathmandu Valley exceed capture, resulting in groundwater table declines. Streams are often important sources of recharge to (or destination of discharges from) aquifers. However, stream-aquifer interactions in the Kathmandu Valley are poorly understood. To improve this understanding, we performed topographic surveys of water levels, and measured water quality, in streams and adjacent hand-dug wells (shallow aquifer). In pre-monsoon, 12% (2018) and 44% (2019) of wells had water levels higher than adjacent streams, indicating mostly a loss of stream water to the aquifer. However, in post-monsoon, 69% (2018) and 70% (2019) of wells had water levels higher than adjacent streams, indicating that monsoon rainfall contributes to shallow aquifer recharge which, at least temporarily, causes streams to transition from losing to gaining. Concentrations of all water quality parameters (electrical conductivity, ammonia, alkalinity, and hardness) were higher in the pre-monsoon compared to post-monsoon in both streams and wells. There was no recurring trend in water level difference longitudinally from upstream to downstream. However, water quality in streams and wells depleted from upstream to downstream. While we clearly observed seasonal refilling of the shallow aquifer, the role of the deep aquifer in seasonal storage processes deserve future research attention.},
keywords = {Groundwater, Kathmandu Valley, Stream-aquifer interactions, Water management, Water quality},
pubstate = {published},
tppubtype = {article}
}

@article{Shrestha2014,
title = {Seasonal variation in the microbial quality of shallow groundwater in the Kathmandu Valley, Nepal},
author = {Sadhana Shrestha and Takashi Nakamura and Rabin Malla and Kei Nishida},
doi = {10.2166/ws.2013.213},
issn = {16069749},
year = {2014},
date = {2014-01-01},
journal = {Water Science and Technology: Water Supply},
volume = {14},
number = {3},
pages = {390--397},
publisher = {IWA Publishing},
abstract = {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. textcopyright IWA Publishing 2014.},
keywords = {Kathmandu Valley, Microbial pollution, Seasonal variation, Shallow groundwater},
pubstate = {published},
tppubtype = {article}
}