Physical Considerations in Managing and Modeling Stream-Aquifer Systems

Aquifers overlain by streams are common throughout the US. The degree to which the streams connect hydraulically with the aquifer is critical to managing the coupled resource. Hydraulic connection controls the rate of exchange of water between the aquifer and stream, and vice versa. Hydraulic connection at a location may vary due to water table depth related to geology or to drawdown in the aquifer, it may vary with distance along the stream channel, and it may vary temporally with stream discharge rate and sediment load. Hydraulic disconnection may occur when there is an unsaturated zone beneath the channel or when a clogging layer develops. This presentation will briefly review the evolution of conceptual models of stream-aquifer hydraulic connections and the implications for resource management. Examples will e provided of data collected along selected western perennial and ephemeral streams.