CONDUIT FLOOD PULSES AS DRIVERS OF DYNAMIC GRADIENTS

Flood pulses through a karst conduit can cause dynamic gradients of head, chemistry and temperature in the conduit and matrix rock. We present a computational fluid dynamics model of a flood pulse in a phreatic karst conduit and adjacent matrix. Dynamic changes in head, non-reactive solute concentration and temperature are tracked. In the matrix, the flood pulse follows a gradient law analogous for bank storage in surface streams. This gradient law dictates the water moves into the matrix rock much faster than it returns. The dynamic patterns of pressure, solute concentration and temperature in the matrix, and time dependent conduit recession curves for these properties are described for the variables of conduit and matrix recharge flow rate, solute and temperature.