People living along the banks of the Mekong River in Laos and Thailand were recently amazed to see the river’s water turn light blue and become so transparent that they could see the sandbars underneath. It was an eye-catching sight and the phenomenon boosted tourism to the area.
Yet the water turning blue is bad news. It shows the river is undergoing an ecological catastrophe.
The Mekong is usually reddish-brown in color as a result of nutrient-rich silt and sediments that permeate the river’s water. Silt-absorbing nutrients like phosphorus and nitrogen are carried by the water flow from upstream to downstream all the way to the open sea in the Mekong Delta in Vietnam.
Along the way the waterborne nutrients nourish aquatic species in the river as well as in its floodplains. This natural sediment system helps support an abundance of agriculture and fisheries in the region where tens of millions of people rely for their daily livelihood on the Mekong across several countries: China, Myanmar, Laos, Thailand, Cambodia and Vietnam.