Water-table fluctuation method for assessing aquifer recharge: application to Canadian aquifers and comparison with other methods

The water-table fluctuation (WTF) method is widely used to assess groundwater recharge but it is also criticized for certain limitations, namely that it is limited to calculating local recharge because most aquifers are relatively heterogeneous. This study aims at assessing groundwater recharge with the WTF method on a bigger spatial scale by comparing results from WTF with those obtained from different methods. The WTF method was thus applied to observation wells located in two aquifers in Eastern Canada for which groundwater recharge had previously been evaluated using several methods. Comparisons were conducted between WTF and other methods appropriate for regional assessments: (1) two water budget approaches, (2) hydrograph separation, and (3) an analytical regional solution based on Dupuit-Forchheimer assumptions. These showed that applying the WTF method to several observation wells and then calculating an average value can yield results that are comparable to those obtained on the scale of catchment areas. The study concludes that the WTF method can be used for the assessment of groundwater recharge at large regional scales if the aquifer is monitored by an appropriate network of observation wells.