Science Daily It's not uncommon for the Oak River, which flows through southwestern Manitoba, CA., to stop flowing at this control dam. A PinP photo. A new study found that between 51-60% of the 64 million kilometres of rivers and streams on Earth that they investigated stop flowing periodically, or run dry for part of the year. It is the first-ever empirically grounded effort to quantify the global distribution of non-perennial rivers and streams. The research, which was published today in Nature, calls for a paradigm shift in river science and management. Story here/