Technical ArticlesESTIMATING SATURATED SOIL HYDRAULIC CONDUCTIVITY USING WATER RETENTION DATA AND NEURAL NETWORKSPachepsky, Yakov A.1; Timlin, Dennis J.1; Ahuja, Lajpat R.2Author Information 1USDA-ARS, Remote Sensing and Modeling Laboratory, Bldg. 007, Rm. 008, BARC-West, Beltsville, MD 20705. Dr. Pachepsky is corresponding author. E-mail: [email protected] 2USDA-ARS, Great Plain Systems Research Laboratory, Fort Collins, CO. Received Jan 11, 1999, accepted April 13, 1999. Soil Science: August 1999 - Volume 164 - Issue 8 - p 552-560 Buy Abstract The modified Kozeny-Carman equation Ksat =Bφen is used to relate soil saturated hydraulic conductivity Ksat to effective porosity φe. However, different values of the coefficient B and the exponent n are found in different data sets. Our objective was to find out whether and how B and n are related to Brooks-Corey's air entry pressure hb and pore distribution index λ. The Southern Region soil hydrologic database of about 500 samples was explored. All soils had both silt and clay content < 70%. Neural networks were used to relate B and n to hb and λ, and a genetic algorithm was applied to find weights in neural networks. Dependencies of B and n on hb and λ had similar shapes. Values of B and n were almost constant for values of λ greater than 1 and were close to 2.6 × 10−3 m s−1 and 2.5, respectively. As the values of λ decreased from 1 to 0, values of B and n decreased. The larger the air-entry pressure, the steeper was the decrease in B and n. © 1999 Lippincott Williams & Wilkins, Inc.