Streams, sewage, and shallow groundwater: stream-aquifer interactions in the Kathmandu Valley, Nepal

Rajaram Prajapati*, Nick N. Overkamp, Niek Moesker, Kate Happee, Rick van Bentem, Anusha Danegulu, Bikesh Manandhar, Amber Bahadur Thapa, Jeffrey C. Davids, More Authors

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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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.

Original languageEnglish
Article number72
Number of pages18
JournalSustainable Water Resources Management
Volume7
Issue number5
DOIs
Publication statusPublished - 2021

Keywords

  • Groundwater
  • Kathmandu Valley
  • Stream-aquifer interactions
  • Water management
  • Water quality

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