Characterizing basin-scale subsurface hydraulic heterogeneity with multiscale geological and hydrological measurements

Abstract

Mapping aquifer heterogeneity is a pressing need for managing regional groundwater resources. Many studies have shown that combining hydraulic tomographic surveys with point-scale geological information is viable for detailing meter-scale to kilometer-scale hydraulic heterogeneity of aquifers. However, due to the complexity of aquifer systems, few field investigations have been conducted on basin-scale systems. In this study, we collected datasets of stream stages, groundwater levels, and borehole logs from 35 wells in a river plain during the wet season, when flood events altered the groundwater flow fields. We then analyzed these datasets using correlation analysis and a geostatistical inverse model. The hydraulic transmissivity and storage coefficient distributions were inverted based on different numbers of geological zones. By validating the estimated parameter fields with independent datasets, we demonstrated that appropriate selection of the number of geological zones, using point-scale geological information and clustering, improved the estimated fields. Further increasing the number of zones beyond an appropriate number deteriorated the estimates at the basin-scale site. The proposed method offers a cost-effective approach for basin-scale characterization. The better knowledge of subsurface hydraulic heterogeneity can support water resource management decisions.