Influence of streambed and aquifer parameters on groundwater-surface water exchanging flux with groundwater flow parallel and perpendicular to the streamflow

Abstract:

Effective water resource management and its allocation require the quantification of groundwater (GW) and surface water (SW) exchanging flux. The exchange is a complex process, and the flux is either measured directly in the field or is quantified using numerical modelling techniques. Modelling techniques identifies two governing components a) streambed and b) the underlying aquifer. The studies have highlighted hydraulic conductivity, thickness and the width of the streambed and the underlying aquifer as key parameters. However, there are limited studies which highlight the effect of individual parameter on the exchanging flux. The present work aims to highlight the significance of individual parameter in a 2D, 2-component, homogeneous, steady-state symmetric stream-aquifer model setup. The parameters are grouped as the hydraulic and geometrical parameters. These parameters were compared individually with the exchanging flux. The streambed conductance (hydraulic conductivity/ thickness) and the hydraulic conductivity of aquifer were observed to follow the logistic relation with the exchanging flux. The higher thickness of the aquifer seems to have no effect on the exchanging flux, and the width of the aquifer defines the point of measurement of head or flux. The study further groups the parameters to a dimensionless factor – conductance ratio (streambed conductance to aquifer transmissivity) and compared it with relative flux (Flux/ Flux_max). The logistic behaviour of this curves suggests the significance of aquifer parameters in the exchanging flux quantification.

The 2D model was able to capture the individual influence of parameters, however, it is limited to the application of different boundary conditions. These boundary conditions represent the GW flow occurring in the underlying aquifer. This 2D model is extended as a 3D model to capture the effect of different setup boundary conditions (as flow parallel and perpendicular to the streamflow). The infiltrating flux follows a logistic relation in both the cases of GW flow. However, the flow parallel to the stream flow shows slight deviations at the higher values of the streambed conductance, which can be investigated in future modelling experiment.