Hanoi People's Committee said changeable weather and discharged waste water are the main causes that killed huge amounts of fish in many lakes in the city.

 About 400 kilograms of fish died in Linh Dam Lake in late October, 2016. 

According to Hanoi People's Committee, changeable weather had lowered the level of dissolved oxygen in the water. Large numbers of people also keep throwing waste into the lakes. Unmanaged fish farming and other businesses on the lakes are also causing pollution.

Statistics from Hanoi Centre for Environmental and Natural Resources Monitoring from 2011-2016 show that the water quality at Hanoi's lakes is getting worse with Van Quan and Giap Bat lakes top the list. The concentration levels of many substances are over the permitted levels.

Hanoi has 117 lakes but most are polluted. Around the lakes are numerous restaurants that throw waste into the lake.

The lakes are also becoming smaller as they absorb more waste.

Hanoi’s authorities asked Hanoi Sewerage and Drainage Company to clean the lakes with Redoxy-3C technology from Germany this year. Businesses around the lakes are also being monitored while projects to improve and control water quality at Hoan Kiem, West Lake and other lakes in the city are urged to speed up.

In the past months, tonnes of fish in many lakes including Dong Da, Linh Dam and Van Quan lakes have died. The most serious case was when 200 tonnes of fish at West Lake died in early October.

Dtinews