ON THE DETERMINATION OF UNSATURATED HYDRAULIC CONDUCTIVITY FROM SOIL MOISTURE PROFILES AND FROM WATER RETENTION CURVES

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Abstract

When solving water flow in a soil using Darcy-Richards' equation, information about the unsaturated hydraulic conductivity of the soil is necessary. However, direct measurement of unsaturated hydraulic conductivity is time consuming and expensive. Therefore, instantaneous profile methods and/or models to estimate the unsaturated hydraulic conductivity from water retention data are preferable. However, results of the instantaneous profile methods are often influenced by how precise we express the relation of measured volume wetness with time and the relation of measured hydraulic heads with soil depth. Here, we introduce three regression functions for expressing these relationships. In addition, an empirical model relating the measured unsaturated hydraulic conductivity with volume wetness was also developed. Evaluations of Burdine and Mualem models to predict the unsaturated hydraulic conductivity from the water retention curves were conducted. The results show Burdine and Mualem models can estimate the unsaturated hydraulic conductivity better for the tested soils at lower volume wetness.

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