Study finds most water flowing into oceans is from groundwater, not rivers

Most water flowing back to the ocean from land is not from rivers, according to a press release from the University of South Carolina. Professor Willard Moore has found the largest source of terrestrial water is actually groundwater, challenging people’s assumptions about water and nutrient flow everywhere.

Moore knew that rocks contain uranium and thorium, which gradually decays into water-soluble radium, which then dissolves into ocean water. Water at varying distances from sea rocks tends to have predictably varying levels of radium. Looking at the actual variation compared to the projected, clues about the water’s flow can be obtained.

Moore also came up with a way of concentrating radium in water samples, as a 200 gallon water sample was needed previously to test for radium. In his new method, Moore was able to concentrate radium from seawater using a manganese solution.

The radium level model he and his colleagues created showed that the only way the levels of radium they were seeing could be reasonable is if the water they were analyzing was not primarily freshwater from rivers and creeks, which typically has much lower amounts of radium, but was instead from groundwater, which has higher levels due to rock exposure.