Last month in China, water levels in Asia’s longest river, the Yangtze, reached an all-time low, and hydroelectric power plants along its course had to slow down or shut down altogether, causing power outages to millions of people.

Over the past five years, fluctuations in surface water levels outside their natural range have been observed in one in five river basins. At the same time, rivers across South Asia are bursting due to increased rainfall and accelerated glacier melt, with the most recent devastating impact in Pakistan.

Although rivers make up a tiny fraction (0.49 percent) of surface freshwater, they play an important role in sustaining life on Earth and human development. Of all the liquid surface fresh water in the world, 87 percent is found in lakes, 11 percent in swamps, and only 2 percent in rivers.

Rivers are highly diverse and productive ecosystems that contribute to economic growth, food security, and human well-being. According to the World Wide Fund for Nature (WWF), globally, an estimated two billion people get their drinking water directly from rivers, and 500 million people (about one in 14 people on earth) live in river deltas that feed on river sediments.