Catchment-Scale Characterization of Intermittent Stream Infiltration: a Geophysics Approach

In arid basins, infiltration through streambeds is considered the primary contributor to groundwater recharge; however, estimating streambed recharge at catchment scale remains a challenge. Moreover, a spatial understanding of streambed infiltration is crucial for estimating where and how much aquifer recharge occurs and where recharge could be enhanced. This study explored the use of continuously sampling shallow geophysical measurements over many kilometers of dry streambed in an intermittent stream basin. In total, approximately 30 km of streambed was traversed, capturing representative portions of first through fifth order stream reaches across the six major soil groups in the study area. The results show a general trend from lower to higher apparent conductivity with change in soil type along the catchment gradient, suggesting a general progression from sandy to clayey soils. The presence of a low permeability layer in the shallowest soils across most soil types and all orders of stream gradient suggests streambed clogging would impair recharge, and that cracking of clays and lateral infiltration is very likely to play an important role in aquifer recharge. This method provided a rapid and relatively simple way to gather information on potential areas for streambed infiltration at a larger scale than is possible with other methods.