Disconnected stream and groundwater interaction: a review

The phenomenon of a stream becoming disconnected from its underlying aquifer commonly occurs in arid and semiarid areas. The interaction between disconnected streams and aquifers is a popular research topic, and over the past few decades, new understanding and methods have emerged. In the present study, we first briefly analyzed the relationship between streams and aquifers. We then reviewed the physical processes and basic principles by which the stream-aquifer system changes from connected to transitional, and subsequently from transitional to fully disconnected, as well as the hydrogeological conditions required for disconnection to occur. For assessing the hydraulic connection between the stream and the aquifer, we synthesized field-based methods based on maximum infiltration rates, critical groundwater tables, or the fluctuations of stream water tables and groundwater tables. The advantages and disadvantages of these methods were analyzed. We also discussed the transient stream-aquifer exchange during disconnection and the effects of heterogeneity on disconnection. We conclude that the basic principles of disconnection are not fully understood. Convenient and reliable methods for assessing the connection status and the effects of heterogeneity on seepage from streams require further investigation in the future.