2 Advances in characterizing groundwater, surface water, and their interactions

This session focuses on characterizing groundwater, surface water, and their interactions through fieldwork, modeling, and data synthesis. We welcome submissions addressing flow, transport, water quality, and water levels under both typical and extreme conditions.

Sunday, 22 March 2026
8:00 AM - 12:00 PM
CCC, Room 25

Improving Understanding of Fluvial Reach-Scale Solute Transport, Hyporheic Exchange, and Uptake Using Breakthrough Curve Fitting and Machine Learning

Paper number: 2-5
Program: Technical Sessions
Time: 9:25 AM – 9:45 AM

Authors

Abstract

Hyporheic zones adjacent to river systems play an important role in attenuating loads of dissolved nutrients and pollutants. Pulse-release breakthrough curves (BTCs) for conservative solutes can elucidate the travel time distribution of water passing through the linked surface water-groundwater system, but field measurements are sparse. To better leverage existing field measurements, we developed a novel curve-fitting model that successfully captured BTC characteristics (r2 ≥ 79%) and enabled the rapid comparison of transport parameters among 319 field studies obtained under a wide range of stream characteristics and flow conditions. Despite the diversity in field locations, study durations, and BTC shapes, optimized curve fitting parameters underscored the widescale prevalence of hyporheic exchange, with a median hyporheic zone mass transfer coefficient of 4 × 10--7 s-1. The same curve-fitting model also successfully represented BTC shape for a particle tracking model (PTM) that simulated the movement of solute parcels within an idealized river system following a pulse release. Finally, we developed a Random Forest (RF) machine learning model to predict reach-scale BTC shape parameters and nutrient uptake within stream systems. While the RF model provided accurate forecasts when much information was provided about stream transport and solute reactivity, its accuracy diminishes with fewer input parameters. Thus, field studies remain a necessary and important tool in understanding hyporheic exchange, though modern predictive tools can improve interpretation.  This work advances our understanding of the complex dynamics of solute movement and uptake in river systems, thus informing stream restoration projects, pollution control strategies, and water resource management.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411488

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