POWER-LAW SCALING OF RESIDENCE TIMES: THE GEOMORPHOLOGICAL SIGNATURE OF GROUND WATER-SURFACE WATER CONNECTION AT NESTED SCALES

Groundwater and surface water are interconnected, and the quality and quantity of both resources are determined by fluxes and storage of water within each component. The interface between ground and surface water is complex and characterized by geomorphological features that vary across scale. Numerical simulations of surface water-ground water exchange across bedforms, bars, bends, and basins show that groundwater has a power-law residence time distribution through all these geomorphological features, providing a foundation and an explanation for temporal fractal behavior in stream chemistry. Since the geomorphological features considered here are typical of most fluvial systems, fractal stream chemistry may be the norm rather than an exception and that it is a natural consequence of ground water-surface water exchange across temporal and spatial scales.