SIMULTANEOUS SCALING OF SOIL-WATER RETENTION AND HYDRAULIC CONDUCTIVITY CURVES

Previously, soil water retention and hydraulic conductivity curves have been scaled independently with separate scale factors calculated for each curve. Here we provide a method to scale both hydraulic functions simultaneously to yield a single set of scaling factors. An algorithm was developed to scale the hydraulic data, either as a function of degree of saturation S, or normalized water content-THETA. Optimization using Powell's method in combination with a Newton-Raphson procedure resulted in one set of parameters representing the scaled mean hydraulic functions and one set of scale factors describing the variability of both the retention and conductivity relationships. We present and compare results obtained from (1) scaling water retention data only; (2) scaling hydraulic conductivity data only; (3) simultaneous scaling of soil water pressure head h and the natural logarithm of hydraulic conductivity K; and (4) simultaneous scaling of the logarithms of both h and K. Sets of scale factors for two data sets were analyzed for distribution type and autocorrelation.