Here in Thailand, and especially around Bangkok, we have a huge network of canals (khlongs) that provide both irrigation and drainage that eventually lead into the mighty Chao Praya river and away into the Gulf of Thailand.
This whole network was created over hundreds of years to protect the capital from flooding as the majority of the area in the central plains around Bangkok sits around sea level. However, there's a problem.
Back in the early twentieth century, an unnamed member of the Royal family, introduced an invasive species of the plant into Thailand from Indonesia, the Water Hyacinth, which in turn had originated in South America. It is said to be one of the fastest growing plants in the world and flourished in Thailand's inland waterways to such an extent that each year, thousands of miles of canals and rivers become carpeted and clogged by this herbaceous imposter. Its main growing season happens to coincide with the rainy season and chaos ensues with flash floods almost day as the Water Hyacinths block drainage channels and water gets backed up.
Time to send out the local council. Better late than never boys!
I was hoping to see a few snakes pop out, or even a huge water monitor lizard but I guess the sound of the diggers and weird harvester boat thing had them all running for cover. The smell though was terrible as they crap on the bottom of the canal got stirred up. These canals are so dirty and full of crap it's untrue.
Hundreds of thousands of tonnes are cleared annually but the good news is, that not all of this ends up in a landfill. Upon reading up, it appears this is quite a useful plant and can be turned into all manner of eco-friendly 'stuff' like cardboard, packaging, and even oil. It just cost me two hours of my life as followed the links and is worth an article in its own right at some time. For now, enjoy the sight of other people doing some serious graft for $12 a day as you sit behind your PC, nursing your Starbucks Frappucino!
Not a problem we have back home in Yorkshire on the Aire and Calder Navigation!

When they arrived, you couldn't see the water as the whole of the surface was carpeted.
The guy on this harvester was dragging the water hyacinths out and pushing them down to where the grab was scooping them out and into trucks.
I'd hate to imagine the number of wee, not-so-timid beasties in each grab load!
And this is how it looks after. Still disgusting and dirty but without the covering. At least now, the water can flow again.
1 HBI share if you can spot the wife in this picture.
Trucks were lining up to be filled. One after another.