In­va­sive wa­ter let­tuce clog­ging Yangtze

China Daily (Hong Kong) - - CHINA - By TAN YINGZI in Chongqing tany­ingzi@chi­nadaily.com.cn

In re­cent days, a large quan­tity of in­va­sive wa­ter let­tuce has ap­peared on the sur­face of the Yangtze River in Chongqing, clog­ging water­ways and threat­en­ing the safety of boats.

Af­ter heavy rains on the up­per reaches of the river last week, the plants washed into Chongqing on Satur­day at about noon. Large amounts soon gath­ered in the mid­dle of the river and along the banks.

On Tues­day, the city’s maritime de­part­ment is­sued a warn­ing and asked boats to avoid the float­ing plants.

The species, in­tro­duced from over­seas, is among the world’s most pro­duc­tive fresh­wa­ter plants. It is found in nearly all trop­i­cal and sub­trop­i­cal fresh­wa­ter ar­eas.

As it of­ten grows into dense

In some back­wa­ter bays, the plants were so dense that a man could stand on them.” Di Hong­wei, em­ployee of Chongqing Wa­ter En­vi­ron­ment Co

mats that clog chan­nels, China has listed it as one of its 100 most dan­ger­ous in­va­sive species. In ad­di­tion, wa­ter let­tuce will also block the ex­change of air, re­duc­ing oxy­gen in the wa­ter and killing fish. Large mats can also block light and al­ter un­der­wa­ter plant com­mu­ni­ties.

At present, the main way to con­trol wa­ter let­tuce is to phys­i­cally re­move it and trans­port it to on­shore dis­posal ar­eas.

This is “the sec­ond time this year” that wa­ter let­tuce has been found in down­town Chongqing, said Di Hong­wei, of Chongqing Wa­ter En­vi­ron­ment Co, which cleans the city’s water­ways.

The com­pany scoops out garbage and storm de­bris to make water­ways more scenic and eas­ier to nav­i­gate.

Flood sea­son is the busiest time of year for river clean­ers. Last month, the com­pany re­moved more than 1,000 met­ric tons of wa­ter let­tuce from the river. The work took a week.

“We didn’t find wa­ter let­tuce last year,” Di said. “But there was a large quan­tity of it in 2015. In some back­wa­ter bays, the plants were so dense that a man could stand on them.”

To speed up the clean­ing, the com­pany has sent three large refuse re­moval boats and hired an­other four to re­move the plants around the clock. It ex­pects to take a week to fin­ish the work.

Chongqing, a megac­ity of 30 mil­lion peo­ple, is lo­cated on the up­per reaches of the Yangtze, the world’s third-long­est river at 6,300 kilo­me­ters.

Since the Three Gorges Dam was built, the river’s wa­ter level rises in win­ter and drops in sum­mer, op­po­site the nat­u­ral cy­cle.

Garbage on the river’s sur­face cre­ates un­pleas­ant scenery and dif­fi­cult nav­i­ga­tion for ships. Trash can even af­fect the pro­duc­tion of elec­tric­ity at the dam. In re­cent years, Chongqing has re­moved more than 5 mil­lion tons of garbage from the river.

RAN WEN / FOR CHINA DAILY

Work­ers deal with wa­ter let­tuce on a refuse-re­moval boat in Chongqing on Sun­day.

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