Unglaublich 😮
Nagdaha Lake was drowning in nutrient pollution. Nepal's fix was 40 floating rafts of bamboo, foam, and trash. Five months later, nitrate had fallen 94% and the fish were coming back.
Nagdaha Lake had once been used for irrigation, washing, and other daily tasks. But decades of household runoff, agricultural fertilizer, and waste from nearby settlements loaded the water with nutrients.
Nutrients don't sound all that bad, but when they build up, they feed runaway algae. When the algae die, microbes consume oxygen while breaking them down. The water can become hypoxic: fish and other aquatic animals are left trying to breathe in a lake with too little oxygen.
Local groups cleaned, dredged sediment and pulled invasive water hyacinth. But the nutrient load kept arriving, so the problem kept coming back.
At the end of 2022, researchers gave the lake something like an artificial root system. They built 40 floating rafts from bamboo, foam, coconut fiber and discarded materials, then planted them with native flowering plants.
The roots hung directly in the polluted water. The plants took up nutrients as they grew, while bacteria living around the roots transformed more of the pollution. Photosynthesis also returned dissolved oxygen to the water.
The rafts covered only 0.34% of the lake. After only five months, nitrate at the best-performing site had fallen by 94%. Iron fell by as much as 95%, and ammonia by as much as 68%.