As many have stated, there ...

As many have stated, there are many uses of water hyacinth.  The challenge however is the harvesting of it from the water bodies.  Also as David Hughs has said, the hyacinth is proliferating due to excessive nutrients in the water bodies, so if you harvest the hyacinth, another macrophyte will take over such as algae, duckweed, etc.  So a holistic approach is necessary whereby sanitation and farming practices are targeted to reduce runoff of untreated or poorly treated wastewater to the streams and rivers, the adoption of control measures on the dams and reservoirs, and sustainable harvesting which is able to produce a useful by-product such as compost, animal feed, biogas, etc.  In South Africa a large dam (Hartbeespoort Dam) infested with hyacinth has been extensively studied  with a number of control measures assessed and some tested including selective fish harvesting (especially bottom feeders that stir up the sediments), introduction of floating wetlands (to create mini- ecosystems) dredging of sediments (which contain some 60 - 70% of the nutrients during the summer stratification), harvesting of both hyacinth and algal mats. Recent activities include compost making in a special process that ensures a commercially acceptable nutrient content of the compost.