Environmental Earth Sciences

, Volume 71, Issue 2, pp 911–922 | Cite as

Chemistry of the heavily urbanized Bagmati River system in Kathmandu Valley, Nepal: export of organic matter, nutrients, major ions, silica, and metals

  • Maya P. Bhatt
  • William H. McDowell
  • Kevin H. Gardner
  • Jens Hartmann
Original Article


Water quality in less-developed countries is often subject to substantial degradation, but is rarely studied in a systematic way. The concentration and flux of major ions, carbon, nitrogen, silicon, and trace metals in the heavily urbanized Bagmati River within Kathmandu Valley, Nepal, are reported. The concentrations of all chemical species increased with distance downstream with the exceptions of protons and nitrate, and showed strong relationships with population density adjacent to the river. Total dissolved nitrogen (TDN), dominated by NH4, was found in high concentrations along the Bagmati drainage system. The export of dissolved organic carbon (DOC) and TDN were 23 and 33 tons km−2 year−1, respectively, at the outlet point of the Kathmandu Valley, much higher than in relatively undeveloped watersheds. The cationic and silica fluxes were 106 and 18 tons km−2 year−1 at the outlet of the Bagmati within Kathmandu Valley, and 36 and 32 tons km−2 year−1 from the relatively pristine headwater area. The difference between headwaters and the urban site suggests that the apparent weathering flux is three times higher than the actual weathering rate in the heavily urbanized Bagmati basin. Fluxes of cations and silica are above the world average, as well as fluxes from densely populated North American and European watersheds. End-member composition of anthropogenic sources like sewage or agricultural runoff is needed to understand the drivers of this high rate of apparent weathering.


Bagmati River Export Trace metals Chemical weathering rates Human population density Kathmandu Valley: Nepal 



The authors thank Jeff Merriam, Michelle Daley, Jody Potter, and Scott Greenwood for their help in the lab and Ronny Lauerwald for his help in drawing the watershed map. Authors also thank the Water and Energy Commission Secretariat, Ministry of Forest and Soil Conservation, Department of Survey-Ministry of Land Reform, Department of Mines and Geology, Central Bureau of Statistics, Nepal Water Supply Corporation, Department of Hydrology and Meteorology, Government of Nepal for providing useful information. The paper benefited from insightful review comments by anonymous reviewers and the authors thank Prof. Gunter Doerhoefer for his suggestions and patience. Thanks to the members of the Aquatic Ecology Center of Kathmandu University for their help and thanks to many individuals for their help during the field work.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Maya P. Bhatt
    • 1
    • 2
    • 3
    • 4
  • William H. McDowell
    • 2
  • Kevin H. Gardner
    • 3
  • Jens Hartmann
    • 1
  1. 1.Institute for the Biogeochemistry and Marine ChemistryKlima Campus: University of HamburgHamburgGermany
  2. 2.Department of Natural Resources and the EnvironmentUniversity of New HampshireDurhamUSA
  3. 3.Department of Civil and Environmental Engineering, Environmental Research GroupUniversity of New HampshireDurhamUSA
  4. 4.Central Department of Environmental SciencesTribhuvan UniversityKathmanduNepal

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