Mavil Aru (Mother River) is a waterway that supplies water to some regions of eastern Sri Lanka.
The closure by the Liberation Tigers of Tamil Eelam (LTTE), a separatist militant organization, of the sluice-gates of Mavil Aru on July 26, 2006, was a crucial turning point in the Sri Lankan Civil War. With the initiation of 'Operation Watershed', the Sri Lanka Armed Forces undertook to wipe out the LTTE. According to Gen. Sarath Fonseka, it was the correct place to start off the military battle to destroy the LTTE. The armed forces launched air strikes with the aim of capturing the waterway and sluice-gates. On August 11, 2006, the Sri Lankan Armed Forces announced that they had gained full control of the sluice gates of the reservoir.