Stream Depletion due to Cyclical Pumping

Stream depletion is defined as the reduction in groundwater discharge flux to a stream resulting from extraction from an aquifer that is hydraulically connected to the stream. Many states regulate the maximum permitted amount of stream depletion, which is typically specified as a percentage of the pumping rate. To demonstrate that a proposed extraction well will not exceed the allowable amount of stream depletion, analytical or semi-analytical solutions are often used. These assume that the applied pumping rate is continuous; however, pumping rates typically vary throughout the year, following a cyclical pattern of high pumping rates in the summer and low pumping rates in the winter. In this work, a new semi-analytical expression was derived to calculate stream depletion resulting from a cyclical pumping pattern. The results of this method were compared to calculations based on a continuous pumping rate equal to the mean value of the cyclical pumping pattern.