Finite Element Implementation of SAFE for Asymmetric Stream-Aquifer Flow Exchange

Area of Science:

• Hydrology
• Environmental Modeling
• Geosciences

Background:

• Interconnected stream-aquifer systems are increasingly impacted by climate change and human activities.
• Current integrated groundwater-surface water models often use empirical parameters for stream-aquifer exchange, limiting physical representation.
• Existing models struggle to capture asymmetric stream-aquifer exchange due to differing groundwater heads.

Purpose of the Study:

• To numerically implement the analytical Stream-Aquifer Flow Exchange (SAFE) formulation within the Integrated Water Flow Model (IWFM).
• To provide a physically based alternative to commonly used first-order exchange (FOE) formulations.
• To evaluate the impact of parameterization differences on simulated stream-aquifer exchange.

Main Methods:

• Numerical implementation of the SAFE formulation in the finite-element-based IWFM.
• Comparison of SAFE with traditional first-order exchange (FOE) formulations like MODFLOW's River Package.
• Testing through hypothetical scenarios and a large-scale regional application.

Main Results:

• The SAFE formulation allows for quantification of asymmetric stream-aquifer exchange.
• Differences in conductance and connectivity parameterizations significantly influence simulated exchange patterns.
• SAFE produces smoother temporal transitions and less short-term variability in simulated exchange compared to FOE.

Conclusions:

• Conceptual model formulation is crucial for accurate interpretation of simulated stream-aquifer exchange.
• The SAFE formulation provides a physically based approach for large-scale integrated modeling.
• SAFE enhances the representation of stream-aquifer interactions in hydrological models.