No trolling, Georg, just good old fashioned decades old experience backed up with science. The wiki article is very nice, and all that vegetation will end up scouring out and depositing in Erhai when there is a decent rain event. Horses for courses.

ummm...did someone happen to ask what will happen when there are big rains and the creeks get gouged and the suspended solids go into the lake? This work was about sustaining the shape of the canals. Plants removing nutrients? Yeah right, there would need to be a Brazilian rainforest there to even make a dent

I recall seeing some 5" gauge models of the steam engines in the old museum. These are real miniature working models, designed to run on ground level steel tracks, that had been constructed by model engineers, don't know from where.
Anyone know if they are they still on display?

Dianchi is there waiting to draw off, just need to clean it up. The present water supply resources and infrastructure are not enough to keep KM supplied in the future.

The history of the water hyacinth use in Dianchi reads like a school science experiment.
Water plants do have a place in the remediation process....if they are managed correctly. This is a popular concept with established wetlands as nutrient sinks.They will take up the nutrients as they grow but then have to be physically removed and processed into mulch, fertilizer or even low grade stockfeed. But they cannot be left to rot in the lake or else the whole nutrient cycle starts over again.
The density of the cover of waterplants also has to be carefully managed or else too much shading and oxygen depletion occurs and as Dan correctly states, they can be a problem.

Even with the best management processes, water plants merely make a very minor dent in the total nutrient loads and, with the basket case that is Dianchi, are at best a tiny contribution to the remediation process.