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WATER RESOURCES RESEARCH, VOL. 42, W05201, doi:10.1029/2006WR004876, 2006

Impacts of the 2004 tsunami on groundwater resources in Sri Lanka

Tissa Illangasekare

Center for Experimental Study of Subsurface Environmental Processes, Division of Environmental Science and Engineering, Colorado School of Mines, Golden, Colorado, USA


Scott W. Tyler

Department of Geological Sciences and Engineering and Department of Natural Resources and Environmental Sciences, University of Nevada, Reno, Reno, Nevada, USA


T. Prabhakar Clement

Department of Civil Engineering, Auburn University, Auburn, Alabama, USA


Karen G. Villholth

International Water Management Institute, Colombo, Sri Lanka


A. P. G. R. L. Perera

Water Resources Board, Colombo, Sri Lanka


Jayantha Obeysekera

Hydrologic and Environmental Systems Modeling Department, South Florida Water Management District, West Palm Beach, Florida, USA


Ananda Gunatilaka

National Science Foundation of Sri Lanka, Colombo, Sri Lanka


C. R. Panabokke

Water Resources Board, Colombo, Sri Lanka


David W. Hyndman

Department of Geological Sciences, Michigan State University, East Lansing, Michigan, USA


Kevin J. Cunningham

U.S. Geological Survey, Miami, Florida, USA


Jagath J. Kaluarachchi

Department of Civil and Environmental Engineering, Utah State University, Logan, Utah, USA


William W.-G. Yeh

Department of Civil and Environmental Engineering, University of California, Los Angeles, California, USA


Martinus T. van Genuchten

George E. Brown, Jr. Salinity Laboratory, Riverside, California, USA


Karsten Jensen

Geological Institute, University of Copenhagen, Copenhagen, Denmark


Abstract

The 26 December 2004 tsunami caused widespread destruction and contamination of coastal aquifers across southern Asia. Seawater filled domestic open dug wells and also entered the aquifers via direct infiltration during the first flooding waves and later as ponded seawater infiltrated through the permeable sands that are typical of coastal aquifers. In Sri Lanka alone, it is estimated that over 40,000 drinking water wells were either destroyed or contaminated. From February through September 2005, a team of United States, Sri Lankan, and Danish water resource scientists and engineers surveyed the coastal groundwater resources of Sri Lanka to develop an understanding of the impacts of the tsunami and to provide recommendations for the future of coastal water resources in south Asia. In the tsunami-affected areas, seawater was found to have infiltrated and mixed with fresh groundwater lenses as indicated by the elevated groundwater salinity levels. Seawater infiltrated through the shallow vadose zone as well as entered aquifers directly through flooded open wells. Our preliminary transport analysis demonstrates that the intruded seawater has vertically mixed in the aquifers because of both forced and free convection. Widespread pumping of wells to remove seawater was effective in some areas, but overpumping has led to upconing of the saltwater interface and rising salinity. We estimate that groundwater recharge from several monsoon seasons will reduce salinity of many sandy Sri Lankan coastal aquifers. However, the continued sustainability of these small and fragile aquifers for potable water will be difficult because of the rapid growth of human activities that results in more intensive groundwater pumping and increased pollution. Long-term sustainability of coastal aquifers is also impacted by the decrease in sand replenishment of the beaches due to sand mining and erosion.

Received 10 January 2006; accepted 9 March 2006; published 9 May 2006.

Keywords: contamination; groundwater; seawater.

Index Terms: 1831 Hydrology: Groundwater quality; 1834 Hydrology: Human impacts; 1832 Hydrology: Groundwater transport; 1884 Hydrology: Water supply.

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Citation: Illangasekare, T., et al. (2006), Impacts of the 2004 tsunami on groundwater resources in Sri Lanka, Water Resour. Res., 42, W05201, doi:10.1029/2006WR004876.