An opposition lawmaker says North Korea gave no notice of plans to release water from the Imjin River and open the sluice gates of Imnam Dam to prevent flooding.

In a National Assembly hearing on the Korea Water Resources Corporation Thursday, representative Shim Jae-chul of the Grand National Party said that Pyongyang agreed in July of last year to give Seoul advance notice of such actions but has not done so since.

Shim claimed that the North must have opened the dam's sluice gates twice in June alone, citing sudden fluctuations in Imjin River water levels even when there was no rain in the region.

The lawmaker urged the government to overhaul its dam management system in areas downstream from the Imjin and Bukhan rivers in preparation for any unilateral dam operations by the North in the future.