Hidden channels of groundwater flow in Tóthian drainage basins

• A stagnation point and streamline analysis is applied to Tóth’s 1963 model.
• Previously undiscovered flow channels are found.
• Regional recharge channels connect to nominal intermediate discharge zones.
• Intermediate recharge channels connect to nominal local discharge zones.
• Basinal centreline asymmetry of stream functions produces the channels.

The classic work of Tóth in 1963 on 2D, steady state, isotropic, basinal, flow modelling is revisited with a stagnation point and critical streamline analysis. It is found that narrow channels of groundwater flow may exist which have previously been undiscovered. Although these channels do not change the overall concept of dividing basinal flow into regional, intermediate and local flow zones, they do show that small portions of recharge areas in regional zones connect with predominantly intermediate discharge zones and also intermediate recharges connect with predominantly local discharge zones. Depending on basin depth and surface potential parameters, the size and capacity of these channels is determined by the existence of paired stagnation points relative to the basin vertical centreline and the degree of asymmetry of stream functions. These channels are likely to occur in other basinal models and will affect the assessment of discharge water temperature, age and chemical composition.