Sri Lanka: wells still damaged by tsunami
Almost a year and a half after the seaquake of December 26, 2004 off Sumatra, around 40,000 drinking water wells on the South Asian island of Sri Lanka are still damaged or completely destroyed by the consequences of the tidal waves that were triggered.
According to Tissa Illangasekare from the Colorado School of Mines in Golden, the tsunamis themselves are not solely responsible for the impairment of the drinking water supply, but subsequent clean-up attempts have also proved counterproductive. The force of the tidal waves damaged many wells near the sea and flushed large quantities of s alt water and pollutants into the mostly open shafts, so that the water was initially undrinkable. At the same time, percolating seawater also entered the aquifers through porous sediment layers made of limestone or sand.
The attempt was then often made to clean up these wells by removing the contaminated or s alty liquids. According to the researchers, however, this turned out to be counterproductive in many cases, as more s alt water could penetrate from the sea through heavy pumping. The subsoil also gave way several times due to falling groundwater levels and the walls of the well collapsed as a result. In most cases, the dirty and s alt water that was pumped out was not cleaned or at least discharged into the sea, but simply drained off in the vicinity of the well, so that it could subsequently get back into the groundwater.
Since many of Sri Lanka's aquifers are located in sandy sediment layers close to the surface, they are mainly replenished by rainwater - which is mostly the case on the island during the autumn monsoon. The regeneration of many wells is correspondingly slow, because they hardly receive any precipitation for most of the year. The monsoon in 2005 brought heavy rain, but the salinity of the aquifers studied only fell slowly. According to the researchers' estimates, the final rehabilitation will therefore take years.
However, there is also good news: The outbreak of diseases caused by contaminated water after the earthquake was prevented because the population was quickly informed about the problem and many wells were effectively disinfected.
