Travel time distributions derived from particle tracking in models containing weak sinks

Area of Science:

• * Hydrogeology and Groundwater Modeling
• * Computational Fluid Dynamics and Transport Phenomena

Background:

• * Particle-tracking analysis in groundwater models with weak sinks often yields uncertain travel time distributions.
• * The ambiguity arises from the unresolved behavior of particles at weak sinks: whether they are discharged or pass through.

Purpose of the Study:

• * To present a novel probability-based method for deriving objective travel time distributions in groundwater models with weak sinks.
• * To enhance the accuracy of groundwater travel time estimations by accounting for particle behavior at weak sinks.

Main Methods:

• * A probability-based method was developed, discharging a fraction of particles at weak sinks based on sink flux to influx ratio.
• * The method was tested on regional groundwater models with coarse (100x100m) and fine (25x25m) resolutions.
• * Travel time distributions were compared between particle-tracking analysis and a solute transport model in a subcatchment.

Main Results:

• * Coarse model particle-tracking underestimated travel times compared to transport solutions or fine model analysis.
• * This underestimation was attributed to the larger area of sink cells and less accurate flow patterns in the coarse model.
• * The probability-based method, especially with fine-resolution models, showed favorable comparison with solute transport solutions.

Conclusions:

• * The proposed probability-based method provides an accurate travel time distribution for groundwater models containing weak sinks.
• * Fine-resolution models are crucial for accurate flow patterns and, consequently, reliable travel time estimations.
• * This method offers an objective approach to resolve uncertainties in particle behavior at weak sinks, improving hydrological assessments.