Overview

• The peer-reviewed analysis reconstructs about 1,300 years of streamflow and finds declines since the early 1990s unmatched by past mega-droughts.
• Two seven-year dry spells from 1991–97 and 2004–10 rank among the longest in the record, with the latter identified as the most severe in more than a millennium.
• The study attributes the fall mainly to reduced summer monsoon rainfall—about a 10% basin-wide decline since the 1950s—exacerbated by groundwater extraction, irrigation diversion and dams.
• Consequences already recorded include 2015–2017 low water that disrupted drinking supplies, irrigation, power and navigation for over 120 million people, with some summer reaches becoming impassable.
• Authors report most global climate models fail to reproduce the observed drying and urge improved monitoring, sustainable groundwater management, environmental flow releases and stronger India–Bangladesh–Nepal coordination.