SPATIAL AND TEMPORAL VARIABILITY OF SOIL HYDRAULIC CONDUCTIVITY IN RELATION TO SOIL-WATER DISTRIBUTION, USING AN EXPONENTIAL MODEL

An internal drainage experiment was conducted to examine soil water co ntent variability in space and in time. It is shown that the flux-grad ient model used to describe water flow in field soil profiles, based o n the Darcy-Buckingham equation, yielded results of extreme variabilit y and questionable validity. The problem lies in the representativenes s of a site due to soil variability, horizontally and vertically in ti me, which added to the character of the hydraulic conductivity versus soil water content relation, which in many cases can be approximated b y exponential functions, leads to coefficients of variation up to 170% in the estimation of soil hydraulic conductivity values. (C) 1998 Els evier Science B,V. All rights reserved.