How Ewald Oldekop discovered the discharge-aridity relationship
Résumé
The recent years have seen a renewed interest in the use of simple mathematical relationships relating streamflow to aridity. Similar or identical formulas have been proposed independently in different places of the world. We wish here to revisit the precursor work of Ewald Oldekop (1911) who was the first to understand the interest of using the aridity index in his formula relating streamflow to precipitation and evapotranspiration.