(1) Lowering of the water table or piezometric surface caused by the extraction of groundwater by pumping, by artesian flow from a bore hole, or by a spring emerging from an aquifer.

(2) Local lowering of the water surface in an approach channel caused by the acceleration of the flow passing over an obstacle or through a control. (ISO/772)



UNESCO/WMO International Glossary of Hydrology (2nd revised ed., 1992)

Posted on February 10, 2014 .