Mixing Enhancement Mechanisms in Aquifers Affected by Hydropeaking: Insights From Flow‐Through Laboratory Experiments

This study presents high-resolution flow-through experiments investigating transport processes in a laboratory setup mimicking an aquifer affected by hydropeaking (i.e., abrupt fluctuations the river stage release or storage of water reservoirs). Highly transient flow conditions were experimentally generated sudden changes level two rivers hydraulic contact with unconfined aquifer. High-resolution image analysis and depth-resolved, high-frequency sampling at outlet allowed monitoring spatio-temporal evolution breakthrough dye tracer plume porous medium. The spreading mixing quantified moment entropy-based metrics scalar field. We show that strongly enhances subsurface (up to 249.5% 41.8% these experiments) demonstrate relevance considering highly regimes properly capture mixing-controlled biogeochemical reactions surface - groundwater interface.