Analysis of river flows from 7250 observatories around the world covering the years 1971-2010 and identified spatially complex patterns, with reductions in northeastern Brazil, southern Australia and the Mediterranean, and increases in northern Europe  . More than half of global rivers undergo periodic drying that reduces river connectivity . Increased frequency and intensity of droughts may cause perennial rivers to become intermittent and intermittent rivers to disappear , threatening freshwater fish in habitats already characterised by heat and droughts . In high-altitude/latitude streams, reduced glacier and snowpack extent, earlier snowmelt and altered precipitation patterns, attributed to climate change, have increased flow intermittency . Patterns in flow regimes can be directly linked to a variety of processes shaping freshwater biodiversity, so any climate change-induced changes in flow regimes and river connectivity are expected to alter
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report