Groundwater discharge from areas with a variable specific drainage resistance

Based on schematic representations of hydrogeological conditions, related to the structure of the formations and topographical features, analytical solutions were derived for the behaviour of groundwater discharge in terms of a time-variable drainage resistance. This led to a general equation of the drainage resistance as a function of groundwater discharge. This physically based equation was implemented in a simple non-distributed conceptual runoff model in order to analyse continuous time series of runoff with intermittent rainfall. Application of the model to different physiographic environments, varying from high Alpine mountainous catchments to the low lying areas of the Netherlands, showed that ignoring the time-variable nature of drainage resistance may lead to significant errors in the analysis and prediction of both baseflow and direct runoff.