Control of water hyacinth is desperately needed. This plant, along with the other aquatic weeds, is dessicating your continent. Figure out how large a market there is for the plant's products, how much of the lake can satisfy that demand, and completely clear the rest, controlling the remaining plant by continuous harvest. Note that the plant is nearly ideal for digestion into methane for a fuel source, and can be processed along with human, food and agricultural waste. Less water for weeds- more water for farms, gardens and drinking cups.