HR: 14:00h
AN: B53A-03    [Abstracts]
TI: DOC and DON Dynamics along the Bagmati Drainage Network in Kathmandu Valley
AU: * Bhatt, M P
EM: mbhatt@cisunix.unh.edu
AF: Department of Natural Resources, 215 James Hall University of NewHampshire, Durham, NH NH 03824
AU: McDowell, W H
EM: bill.mcdowell@unh.edu
AF: Department of Natural Resources, 215 James Hall University of NewHampshire, Durham, NH NH 03824
AB: We studied organic matter dynamics and inorganic chemistry of the Bagmati River in Kathmandu valley, Nepal, to understand the influence of human and geochemical processes on chemical loads along the drainage system. Population density appears to be the most fundamental control on the chemistry of surface waters within the Bagmati drainage system. DOC concentration increases 10-fold with distance downstream (from 2.38 to 23.95 mg/L) and shows a strong relationship with human population density. The composition of river water (nutrients, Cl) suggests that sewage effluent to the river has a major effect on water quality. Concentrations were highest during summer, and lowest during the winter monsoon season. In contrast to DOC, DON concentration shows surprisingly little variation, and tends to decrease in concentration with distance downstream. Ammonium contributes almost all nitrogen in the total dissolved nitrogen fraction and the concentration of nitrate is negligible, probably due to rapid denitrification within the stream channel under relatively low-oxygen conditions. Decreases in sulfate along the stream channel may also be due to the reduction of sulfate to sulfide due to the heavy organic matter loading. Water quality is unacceptable for any use and the whole ecosystem is severely affected within the urban areas. Based on a comparison of downstream and upstream water quality, it appears that human activities along the Bagmati, principally inputs of human sewage, are largely responsible for the changes in surface water chemistry within Kathmandu valley.
DE: 1871 Surface water quality
SC: Biogeosciences [B]
MN: 2005 Joint Assembly