Characteristics of Stream-Groundwater Systems under Losing Streams without Clogging

Abstract:

The stream-groundwater system is one of the most important components of hydrologic cycle. Losing streams (either connected or disconnected) are widespread in arid and semi-arid regions, but have not been fully understood, especially for the disconnected type. This study is devoted to investigate the evolutional process of seepage flux, pressure head and flow states, and it constructs a new theoretical framework for characteristics of stream-groundwater system under losing streams without clogging. This study focuses on investigating the transition among different evolutional states and the critical conditions of transition between the connected and the disconnected states. The results show that there are three primary evolutional states of a stream-aquifer system: a disconnected state, a transitional state and a fully connected state. More specifically, this study shows that between the stream and aquifer, there is 1) a connected zero flux zone, 2) a disconnected zero flux zone and a connected unsaturated zone, 3) a connected saturated zone with a connected negative pressure zone, and 4) a connected saturated zone with a connected positive pressure zone. The corresponding critical conditions are that 1) the zero flux zone starts to disconnect, 2) the unsaturated zone starts to disconnect, and 3) the negative pressure zone starts to disconnect. Overall, this study provides a detailed quantitative analysis on the evolution of a stream-aquifer system from a connected state to disconnected state when the clogging layer is missing.