Pedotransfer functions for soil hydraulic properties developed from a hilly watershed of Eastern India

Abstract

Saturated hydraulic conductivity ( K s) and water retention characteristics (θ − h) of soil are needed to characterize the hydrological response of watersheds. Direct measurement of these two hydraulic properties at multiple locations in a watershed is time-consuming and costly. Alternatively, pedotransfer functions (PTFs) may be used to indirectly estimate these properties from easy-to-measure soil properties. However, in many developing countries such PTFs are not available because of the lack of large databases typically required to develop PTFs. In this study, PTFs were developed from a limited number of soils collected from a hilly watershed located in the Western Catchment of the Chilika Lake, Orissa, India. Point PTF for K s and parametric PTFs for the parameters of van Genuchten water retention model were developed through multiple linear regression technique. Soil texture, organic carbon contents, pH, and elevation were used as the input variable for these new PTFs. These PTFs were validated against the two national datasets on the Benchmark Soils of India and those representing the Indo-Gangetic Plains. All the three PTFs showed the best performance when applied to soils of the watershed from where the PTFs were developed. When applied to soils outside the study area, these PTFs performed similar to established PTFs, which are generally derived from very large databases. A significant result of this study is that robust PTFs may be developed from a limited number of soil samples provided there is sufficient variability in soil properties. This study shows that soils collected from hilly watersheds may possess such variability. Small area of a watershed is also convenient to collect large number of soil samples needed to develop robust PTFs.