HR: 17:30h
AN: H14D-06    [Abstracts]
TI: Ponds and Rice Fields: The Hydrology and Chemistry of Aquifer Recharge in Bangladesh
AU: * Neumann, R B
EM: rneumann@mit.edu
AF: Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
AU: Harvey, C F
EM: charvey@mit.edu
AF: Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States
AB: The shallow aquifer in Bangladesh, which provides drinking water for millions and irrigation water for innumerable rice fields, is severely contaminated with naturally occurring arsenic. Water balance calculations show that surface ponds and irrigated rice fields are the primary sources of recharge to this contaminated aquifer. Recharge from an individual rice field is both temporally and spatially heterogeneous, whereas flow from a pond is more constant and uniform through the pond sediments. Rice field recharge is focused through bunds (the berms surrounding the field), and depends on irrigation intervals. Field flow patterns are controlled by cracks and the development of an unsaturated zone. The water chemistry of these two recharge sources is distinctly different. Compared to the rice fields, ponds contribute recharge with a higher organic carbon load and increased concentrations of solutes associated with anoxic microbial respiration. The differences in the recharge behavior and solute loads of these two sources may explain the spatial patterns of groundwater chemistry that control arsenic concentrations.
DE: 0471 Oxidation/reduction reactions (4851)
DE: 1831 Groundwater quality
DE: 1834 Human impacts
DE: 1842 Irrigation
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: 2007 Fall Meeting