RBFsim – A tool for early planning stage of riverbank filtration systems

Abstract

Riverbank filtration (RBF) is increasingly being considered an effective method to support the management of water supply and the management of groundwater-river water exchange. Literature, however, provides very limited methods for the initial evaluation of the RBF system. Specifically, initial evaluations need to rely on limited data, be cost-effective, and provide sufficient useful output. The paper provides the development of a tool called RBFsim, designed for the early assessment of flow hydraulics in a riverbank filtration (RBF) scheme during site selection and optimization of well operation. The developed tool allows simplified computation (based on the Analytical Element Method or AEM) of the flow field for single and multiple wells in a 2D homogeneous and isotropic aquifer with uniform flow. The tool superimposes analytical solutions for key RBF quantities such as residence time (the time required for river water to reach the well) and the proportions of water (contributed by the river and groundwater) in the well discharge. These solutions are superimposed on the developed flow field. Additionally, the tool can be used to evaluate the impact of riverbed clogging on the operation of the RBF system. The simplified computation due to AEM and limited data requirements allows the tool to be used in handheld (smartphones) or desktop devices with or without internet connection. RBFsim results are verified by comparing them with results from MODFLOW and MODPATH simulations, which are based on entirely different (finite difference) computational schemes. The obtained results from both these models match within the error margin of less than 5%. Further, the practicality and applicability of RBFsim are illustrated using synthetic and field data. While the tool provides a matching river water contribution ratio with field data, it demonstrates the best-fit residence times primarily for higher well discharge rates. These limitations are attributed to complexities observed in the field, such as a heterogeneous aquifer and nonuniform flow. Overall, the developed tool simplifies the complex computations required, particularly for assessing the feasibility and risk of RBF schemes. The developed tool’s methods and code are open-sourced (licensed under CC-BY 4.0), which promotes personalized modifications and extensions.