Seepage Flux
Seepage Flux is the magnitude and direction of water movement at the interface between surface water and groundwater systems.
In connected water resources, the flow of water between the surface water feature and the aquifer is termed the seepage flux. The term seepage usually relates to the flow of water through porous medium (such as sediments). The term flux relates to the flow rate of fluid (or particles or energy) through a given surface area. Hence seepage flux relates to the direction and rate of water movement through the stream-aquifer interface (such as the stream bed). This is measured in terms of volume per unit area per unit time. In SI units this translates to m3/m2/day or alternatively m/d, however other units of measurement reported from studies include m/s, L/m2/d, mm/d or cm/d. Flux can also be aggregated over the area of the surface water feature. For example, seepage flux for a stream reach is often expressed in units of m3/d/km (or ML/d/km) by incorporating stream channel width. The convention is that positive seepage flux values indicate flow of groundwater to the surface water feature (also referred to as discharge or outflow) and negative flux values indicate flow from the surface water feature to the aquifer (also referred to as recharge, reverse flow or inflow), refer Figure 1
Figure 1: Vertical directions of seepage flux (from Sebestyen & Schneider, 2001)
References
Sebestyen SD, Schneider RL, 2001. Dynamic temporal patterns of nearshore seepage flux in a headwater Adirondack lake. Journal of Hydrology 247:137-150.