Lanka water supply still suffers effects of tsunami

Washington, May 10: Sri Lanka's coastal drinking water supply continues to suffer from the effects of the December 2004 Indian Ocean tsunami, which caused widespread death and destruction in the region.

Much of the island nation's coastal area relies for water consumption on wells, usually hand-dug and relatively shallow. Some 40,000 such wells, each typically serving several families, were destroyed or contaminated by the tsunami, a new finding revealed.

According to a research report titled ''Impacts of the 2004 Natural Disaster on Groundwater Resources in Sri Lanka'' funded by US National Science Foundation with support from Sri Lanka National Science Foundation and Soil Science Society of Sri Lanka, long-term sustainability of aquifers that supply water to wells is in doubt because of continued salt water contamination, beach erosion and human impacts such as sand mining, increased pumping and pollution.

The 14-member team from the United States, Sri Lanka and Denmark, reported its findings in a paper published here yesterday in the American Geophysical Union journal 'Water Resources Research'.

During investigations from February through September last year in Sri Lanka, the team found that the natural disaster had affected coastal drinking water sources in several ways. The tsunami, which reached up to 1.5 km inland, poured sea water and other contaminants directly into the open dug wells, making those that were not destroyed unusable.

In some areas, as many as four large tsunami waves struck. In addition to well contamination, large quantities of sea water penetrated from the flooded surface of the land through porous layers below and into the aquifer, the findings said.

Efforts to restore wells by pumping out sea water sometimes seemed counterproductive because excessive pumping might have allowed more sea water to enter the aquifers from below.

Although some affected coastal aquifers in the island nation are composed of ancient limestone deposits, especially in the north, most coastal groundwater is stored in sandy aquifers that are replenished by rainwater, mostly during October-February monsoon season.

This ''recharge'' has been slow in many of the most affected areas because they did not receive substantial rainfall for almost a year.

The December 2005 monsoon rains were substantial, but the researchers say it will take several more monsoon seasons for the aquifers to recover.

In collaboration with the American, Danish and Sri Lankan scientists, a group of researchers at International Water Management Institute in Sri Lanka is conducting long-term studies at selected sites.

Planning is under way to provide piped water to many coastal villages, to supplant the individual -- and vulnerable -- open dug wells.

Other social responses include plans for expanding centralised sewage collection, proposed setbacks for housing along coastlines and the use of new modeling techniques for integrated management of surface water and groundwater for sustainable use of water resources.

The team has prepared recommendations that will be presented to the Sri Lankan government to help develop local expertise and capacity building in modeling, data management and sub-surface characterization for integrated water management in the affected regions. The authors are continuing to work together to address Sri Lanka's water needs, a release said.

UNI