There are three types of ...
Published by Luis Bravo-Inclán, Senior researcher at Mexican Institute of Water Technology
There are three types of water hyacinth control: Mechanical, chemical or biological. The first two are the ones that give more rapid results for tropical high infested lakes and reservoirs (as your own example in Africa). Note, do not, I mean do not use chemical control if the water is used as a drinking source. Biological control is the less a an enviromental and antrophogenic problem issue, but it is used for mild, not excesive weed infestations, as a maintenance activity.
In Mexico, this problem have been a tough experience, with a high nutrient level in lakes and a warm water tropical scenario. There has been a lot of studies in relation to the possibility of gaining money (or at least, good economical control action) with, for example, use the weed for making a compost, or a biofuel, cattle food, etc. but the reality is that --after a lot of research-- the practical use of this weed is way high more expensive and difficult that the conventional practices, so this has been a hard situation.
Weeds are related to eutrophication problems in your lake so, besides having a strong water weed mechanical control, for example, there is the need to control the nutrients (P and N) that enter this water body, specially the waste water pollution, and other point pollutions that could be, in the first time, more easily to monitor and also to control with very low levels of nitrogen and phosphorous. After that, you need to study your basin, and to implement good practices that limit the entrance of solids, organic matter and nutrients in your lake.
Good luck! Luis
P.D.- This article might help you,