Determination of soil hydraulic properties in a part of Hindon river catchment using soilprop software

Abstract

Mathematical models of hydrologic and agricultural systems require knowledge of the relationships between soil moisture content (8), soil water pressure (h) and unsaturated hydraulic conductivity (K). To model the retention and movement of water and chemicals in the unsaturated zone, it is necessary to know the relationships between soil water pressure, water content and hydraulic conductivity. It is often convenient to represent these functions by means of relatively simple parametric expressions. The problem of characterizing the soil hydraulic properties then reduces to estimating parameters of the appropriate constitutive model. A number of models for water retention function and unsaturated hydraulic conductivity are well reported in literature, the most popular being van Genuchten model and Brooks-Corey model. In general, the van Genuchten model matches experimental data more satisfactorily than Brooks-Corey model. However, the functional form of van Genuchten model is complicated and limits its usefulness for large number of analytical solutions available for infiltration and drainage problems. On the other hand, Brooks-Corey model yields conductivity and water retention functions that are easy to manipulate mathematically. For this study, 27 soil samples were collected from various locations as well as depths in different villages, namely Aurangabad, Kamalpur, Budhakhera, Gagalheri, Dudhil Bukhara in the upstream part of Hindon river catchment and laboratory investigations were carried out to determine bulk density and grain size distribution. Using these data as input to the SOILPROP software, van Genuchten and BrooksCorey parameters (a and n & hd and A.) were determined to derive the retention characteristic and unsaturated hydraulic conductivity. The values of a and n (van Genuchten parameters) were found to vary from 0.00004 to 0.00078 and 1.19 to 1.65 respectively. The values ofhd and A. (Brooks-Corey parameters) were found to vary from 860 to 20200 em and 0.189 to 0.538 respectively. These results (as necessary input for unsaturated zone modelling) will be helpful for prediction of soil moisture flow and groundwater recharge in the Hindon river catchment.