Flow of Ground Water to a Well Near a Stream – Effect of Ambient Ground‐Water Flow Direction

Abstract

ABSTRACTAn analytical model has been developed to evaluate and improve our knowledge of steady‐state flow of ground water toward a well near a stream. This model differs from others in that the direction of ambient ground‐water flow (i.e., regional ground‐water flow) does not have to be perpendicular to a gaining stream, but can be oriented in any direction. Without using measured water levels, flow directions and rates can be calculated, i.e. estimated flow nets can be drawn based on the pumping rate, the ambient ground‐water flow rate and direction, and the location of the well and stream. The model can be used to help determine the minimum rate of pumping that will induce infiltration from a stream to a well, and the components of pumping that are derived from the stream and the aquifer. The areal distribution of flow includes: a zone of induced infiltration from a stream toward a pumping well denoted the stream capture zone, a zone that includes all ambient ground water captured by a pumping well called the aquifer capture zone, and a zone downstream of the stream capture zone where water flows from the stream into the aquifer and then back to the gaining stream called the zone of induced throughflow. Each zone could be distinct geo‐chemically. The concepts elucidated by the model are useful for ground‐water pollution studies and for planning purposes. Normalized curves are presented to quickly determine the estimated boundaries between the stream capture zone and the zone of induced throughflow. An example of induced streamflow from Albuquerque, New Mexico illustrates application of the model.