Fluctuations are generally due to one of three major factors: 1) change in the volume of water stored in the aquifer, 2) changes in atmospheric pressure, and 3) changes caused by aquifer deformation. (And did you also know that many factors may affect river discharge, including dams and the diversion of water for agriculture and industry. The researchers found, however, that the reduced flows in many cases appear to be related to global climate change, which is altering precipitation patterns and increasing the rate of evaporation.)
