Mr Ta Van Son, Deputy Head of the Department said that the mud layer on the lake's bed was between 60 and 80 centimeters, which was the main cause for the polluted water.

The Hanoi authority has applied numerous measures to desilt the lake. The lake was repaired to ensure it did not receive waste water from sluices, but added about 500 to 800 cubic meters each day in the dry season, and dredged mud and rubbish from around the lake.

The results of the water quality analysis showed that pollution levels had dropped, the oxygen had increased, and the living environment for creatures had also improved.

However, he said, these were temporary measures and did not assure its sustainability.

According to the department, the removal of the mud would bring better results if it was implemented accurately.

In 2009, the city had used SediTurtle, a German-technology robotic sediment collector, as a pilot to dredge 114,000 square metres of the lake. The project had reportedly improved the lake while doing no harms to turtles./.

( VNF )