Time Net for Ground-Water Flow in Idealized Coastal Wedge

Abstract

The classic Glover model for head and stream function in an idealized coastal wedge of fresh ground water in a homogeneous and isotropic aquifer is extended to estimate the length of time for fresh ground water to flow to the outflow face (“exit time"). An analytical solution is given for the exit time (τ) for water that travels the streamline that lies at sea level and τ's for water traveling deeper streamlines are found numerically by summing incremental travel times as water is tracked incrementally along a streamline. Results are given by dimensionless "time nets," which show streamlines and contours of dimensionless exit time, and thereby allow estimation of exit time for many combinations of hydraulic conductivity, porosity and fresh-water discharge. The model ignores the presence of an underlying transition zone and, therefore, applies only to the part of the wedge that lies shoreward of the effects of the lower boundary on the configuration of the interface and other isochlors.