Estimating Exchange Fluxes Between Surface Water and Groundwater Using Stable Isotope and Radon Models

Posted by  Jason Lillywhite

I'm excited to share a recent paper by Lloyd Townley and Jeffrey Turner, which showcases the use of GoldSim software in modeling surface and groundwater interactions. The research introduces the Lake Water Balance Calculator (LWBC), a tool developed using GoldSim, to estimate groundwater-surface water flow rates. This tool leverages transient balance solutions for radon, coupled with volumetric flow equations, and presents results from multiple case studies.

LWBC dashboard in GoldSim

The paper emphasizes the complexities of groundwater flow patterns near surface water bodies and the importance of understanding these interactions. By providing a consistent conceptual and simulation modeling framework, the authors help practitioners better understand surface water-groundwater interactions and guide efficient field data acquisition. The LWBC is useful for designing and implementing short-term field studies, offering a powerful method for estimating groundwater inflows and outflows.

Link to paper: Consistent solutions for simultaneous dynamic water, solute, stable isotope and radon balances to estimate average exchange fluxes between surface water bodies and groundwater - ScienceDirect

GoldSim played an important role in this research by providing a high-level graphical programming environment that allowed the authors to represent balance equations and validate results. The LWBC enables users to estimate the magnitude of groundwater inflow and outflow, which cannot be measured directly.

Coupled balance of abundant and rare isotopes of hydrogen using GoldSim

Case Studies

The LWBC is demonstrated through three case studies: Perry Lakes East, Lake Jasper, and Georgetown Billabong in Australia. 

Perry Lakes East: The LWBC analyzed the recession stage over a short period, quantifying the relative magnitudes of evaporation and groundwater outflow, providing insights into the sustainability of artificial lake level maintenance.

LWBC results for Perry Lakes East: (a) volume fraction remaining, (b) chloride concentration, (c) field data compared to results.

Lake Jasper: The LWBC tested the conceptual flow-through model and quantified components of its water balance, providing a good fit for observed data and confirming the lake's flow-through characteristics.

Simulated and observed water level, Lake Jasper, Western Australia

Georgetown Billabong: The LWBC investigated surface water-groundwater interaction during the dry season, with radon as an additional constraint, providing a consistent match for water, chloride, stable isotope, and radon balances.

Volume fraction remaining for Georgetown Billabong

Conclusion

This research highlights the importance of a consistent approach to estimating exchange fluxes between surface water and groundwater. The LWBC GoldSim model provides a valuable tool for understanding these interactions, enabling practitioners to achieve a rapid initial understanding and guide efficient field data acquisition.