Hydraulic Architecture of the Brazos River Alluvial Aquifer

Geophysical and hydrogeological data can be used to estimate aquifer hydraulic parameters and test alternative conceptual models of subsurface hydrology. Here we confirm the existence of a relic sand-dominated channel-belt in an alluvial floodplain using electrical resistivity tomography and time-domain electromagnetics. After converting the bulk resistivity structure to porosity, we use hydrological modeling to gain new insights into the hydraulics and compartmentalization of a heterogeneous alluvial floodplain aquifer system. We discovered that rainwater infiltration fills the initially dry channel-belt laterally rather than from direct infiltration from above. This new understanding of preferential flow paths around and into sand-dominated channel-belts outlines how the architecture of an alluvial floodplain determines its response to natural hydrologic disturbances, thereby providing an improved basis for making informed decisions about water management strategies.