HR: 09:30h
AN: H51K-07    [Abstracts]
TI: Effect of Tsunami on Shallow Ground Water Quality in Sri Lanka; Field Observations and Geochemical Modeling
AU: * Vithanage, M
EM: meth´@geol.ku.dk
AF: Department of Geography and Geology, Østervoldgade 10, Copenhagen, 1350, Denmark
AU: * Vithanage, M
EM: meth´@geol.ku.dk
AF: International Water Management Institute, Sunil Mawatha, Battaramulla, 1350, Sri Lanka
AU: Villholth, K
EM: k.villholth@cgiar.org
AF: International Water Management Institute, Sunil Mawatha, Battaramulla, 1350, Sri Lanka
AU: Mahatantila, K
EM: kusheem@yahoo.co.uk
AF: Department of Geology, University of Peradeniya, Sri Lanka, Peradeniya, 1350, Sri Lanka
AU: Engesgaard, P
EM: pe@geol.uk.dk
AF: Department of Geography and Geology, Østervoldgade 10, Copenhagen, 1350, Denmark
AU: Jensen, K
EM: khj@geol.ku.dk
AF: Department of Geography and Geology, Østervoldgade 10, Copenhagen, 1350, Denmark
AB: On December 26th 2004, the earthquake off the south coast of Sumatra in the Indian Ocean generated tsunami waves, resulting in severe devastation in the coastal regions of Sri Lanka. Changes in water quality of a sand aquifer on the east coast of Sri Lanka due to the tsunami, subsequent disturbance due to well pumping and flushing by precipitation were investigated to observe its "natural cleansing" response by precipitation and the effect of well cleaning and pumping of water for domestic uses. The selected field sites near Batticaloa, located on the east coast of Sri Lanka, are bordered by the sea to the east and a lagoon to the west. The two sites were classified as disturbed and undisturbed, based on groundwater pumping. Daily rainfall was measured at the site and changes in water table were monitored from October, 2005 to October, 2006. Water samples were collected from 15 dug wells and 20 piezometers, from the disturbed and undisturbed sites, respectively to evaluate the temporal and spatial trends in water quality. Observed values of electrical conductivity, alkalinity and concentrations of calcium, sodium, magnesium, potassium and sulphate in the disturbed site were slightly higher than that in the undisturbed site during the months of January, March, and October 2006. Furthermore, water quality parameter values in abandoned dug wells in the disturbed site have shown similar results as the undisturbed site. This was also evident from the geochemical inverse modelling using the U.S. Geological Survey code, PHREEQC. These findings support the hypothesis that well cleaning and abstraction of water for general purposes disturb the natural downward movement and the recession of the tsunami impacts and therefore, the imprint of the tsunami may have been prolonged in the disturbed site compared to the undisturbed site.
DE: 1829 Groundwater hydrology
DE: 1830 Groundwater/surface water interaction
DE: 1831 Groundwater quality
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting