Lake Shihwa was notoriously called as ‘the Lake of Death’ after the completion of its tidal embankment in 1994. Lake Shihwa became a national synonym for water pollution and made a big impact on public recognition of the coastal environment. Water pollution in Lake Shihwa brought into social controversies and heated debates due to the negative side effects of reclamation projects.

After the construction of the seawall, the water quality of the lake quickly deteriorated as the industrial wastewater and domestic sewage from the area had come into the lake. In 1997 the record for the worst water quality was 18㎎/L of mean COD concentration. Seawater started being circulated through sluices to improve water quality and mean COD concentration decreased to 4~6 ㎎/L since 2000. However, seawater influx through sluices at the edge of embankment doesn’t reach the upstream of Lake shihwa and anoxia occurs repeatedly at the bottom of the lake every summer.

As a countermeasure to improve the water quality, the tidal power plant was built for the seawater circulation and has been operating at full capacity since December, 2011. With the operation, the annual mean water quality will be improved as same as the water quality of a faraway ocean and the creation of new tidal flats in the upstream will provide a habitat for various species including migratory birds. However, the possibility of side effects of the tidal power plant is present, so the marine environment is being closely monitored.