The Tortuous Path of Water Molecules through Soil and the Hydraulic Conductivity Function.

Water molecules in soil are driven along a tortuous pathway by a variety of forces. The macroscopic result is a flux of water that is related to the hydraulic gradient via the hydraulic conductivity. Since the early 50’s great progress has been made to predict the hydraulic conductivity function from hydrostatic data. The Burdine and Mualem integrals provide the basis for this prediction. Solutions for these integrals are now readily available on PC’s in terms of incomplete gamma functions. There is no further need for assumed relations between the hydrostatic parameters leading to closed-form (analytical) solutions. The remaining unsolved mysteries are of a microscopic, geometric nature. They may be called "tortuosity" or "connectivity". "Patterns of behavior" will be presented showing the macroscopic (cumulative) effects of these microscopic intricacies.