Guangxi is in a traditional karst region, where natural depressions caused by
groundwater recession and erosion are not uncommon.
The critical time is the time it takes the
groundwater recession curve to reach a stable shape after the recharge period.
The shape of the
groundwater recession curve (linear rather than concave or convex) after the 8 August rainfall event suggests that water movement from this aquifer is a combination of vertical and horizontal fluxes (Smith and Hebbert 1983).