A severe drought that has caused water levels in Southeast Asia’s Mekong River to drop to their lowest in more than 100 years could have devastating consequences for fish, as well as the tens of millions of people living and working along the river, experts warn.

The crisis began when critical monsoon rains, which usually start in late May in the Mekong region, failed to arrive. Dry conditions, driven by the El Niño weather phenomenon and exacerbated by climate change, persisted well into July. At that time, observers say, the situation was made worse by hydropower dam operators upstream, in China and Laos, withholding water for their own purposes.

Although the rains finally began to fall in the