A new study by scientists from McGill University and INRAE ​​found that 51% to 60% of the 64 million kilometers of rivers and streams on Earth periodically stop flowing at least once a year.

The new study is the first-ever empirically based attempt to quantify the global distribution of volatile rivers and streams. The map of variable freshwater sources resulting from this work, the first of its kind, also provides important baseline information for assessing future changes in river flow intermittency. And also to determine and monitor the role of these rivers and streams in global aquatic and biochemical systems.

Continuous rivers and streams are very valuable ecosystems as they are home to many different species that are adapted to the cycles of the presence and absence of water. In addition, these rivers are vital as sources of fresh clean water and food for people. The authors of the study note that the problem is that more often than not, these resources are mismanaged or completely excluded as irrelevant when it comes to conservation laws.

Given the ongoing global climate and land-use change, an increasingly significant portion of the global river network is expected to stop seasonal flow in the coming decades.

The study found that many previously flowing rivers and streams over the past 50 years dry up at least once a year due to climate change, land-use change, or temporary or permanent withdrawal of water for human and agricultural use.