Flow and residence time in a two-dimensional aquifer recharged by rainfall

Abstract

Abstract

Soft matter physics of the ground beneath our feet

“…Even in steady-state, the residence time of water in an aquifer is not just inversely proportional to the rainfall rate, because the volume of groundwater needs to accommodate the flux it carries -V is a function of R, and the determination of this function is still an open problem. 287,293 In reality, of course, precipitation is intermittent, and so is the rainfall it generates. Since the groundwater flow is nonlinear, one cannot expect that a time average will gracefully propagate through the equations, as it would in a linear system.…”

“…How long does the subsurface part of this travel take? The residence time of water in an aquifer is where V is the groundwater volume, A is the area of the catchment, and R is the rainfall rate 287 (typically expressed in mm year −1 ). Residence time is thus tantamount to storage.…”

“…11 shows the stationary flow of groundwater through deep, unconfined aquifers that discharges into neighboring streams. 287 As the rainfall rate increases, the water table rises. The domain over which the flow equations need to be solved thus expands, and this makes the problem non-linear.…”

“…Even in steady-state, the residence time of water in an aquifer is not just inversely proportional to the rainfall rate, because the volume of groundwater needs to accommodate the flux it carries – V is a function of R , and the determination of this function is still an open problem. 287,293…”