Hi Mehul,  I am inclined to ...

Hi Mehul, 

I am inclined to agree with Dave (and not just because I am also from South Africa) and Sameer's comments - the reason why the hyacinth is growing in the first place is because your river water is nutrient rich (or to put it bluntly - polluted with organic waste material). 

I believe Dave's solution will be your best bet in the long term - provided that you are able to implement a solution to eradicate the nutrient oversupply from the river - an example in South Africa where this has proven very difficult to achieve is the Hartebeespoort Dam, and the reason is that a lot of Johannesburg's wastewater is discharged into the dam's catchment rivers keeping the nutrient loading very high and encouraging Hyacinth growth. (Have a look at the site on Google earth) 

Sameer's solution, to manage the growth, in the short term, although it is a long term solution as well, is your best bet whilst the river is contaminated with excess nutrients. 

I can suggest a few options in this regard. If you're interested, contact me on email rob@selectra.co.za 

I look forward to hearing from you

Kind regards

Rob