Abstract:
Soil hydraulic conductivity is simply the ability of a soil to transmit water impacts
almost every soil application. It is critical for understanding the complete water balance and
is also used for estimating groundwater recharge through the vadose zone. Agricultural
decisions are based on hydraulic conductivity for determining irrigation rates or to predict
erosion or nutrient leaching. And it is used to determine landfill cover efficacy. Hydraulic
conductivity is defined as the ability of a porous medium to transmit water under saturated or
nearly saturated conditions. Unsaturated soil hydraulic conductivity is a main parameter in
agricultural and environmental studies, necessary for predicting and managing water and
solute transport in soils which refers to a measure of soil's water-retaining ability
when soil pore space is not saturated with water.
The objective of this study was to compare unsaturated hydraulic conductivity of
different soils. Double ring infiltrometer experiment were conducted at KCAET, Tavanur
campus. It comes under Malappuram District of Kerala state in India. Two sets of infiltration
readings were collected from two different locations coming under different soil groups.
HYDRUS 1-D software is used to calculate unsaturated hydraulic conductivity of soil
by inverse modelling. The HYDRUS program numerically solves the Richards equation for
variably saturated water flow and advection-dispersion type equations for heat and solute
transport. The cumulative infiltration flux across a boundary at different time was used as the
input variable to optimise the soil hydraulic parameters. Hydrus-1D software is used for
inversion of six soil hydraulic parameters including saturated water content (θ s ), residual
water content (θ r ), saturated hydraulic conductivity (K s ), soil water retention parameter (n),
inverse of air entry value (α) and pore connectivity parameter (l) which is further optimized
using Marquardt-Levenberg optimization algorithm. The optimised parameters were fitted to
the empirical models proposed by van Genuchten (1980) for finding the unsaturated
hydraulic conductivity (K) of the proposed soils. The study gives the conclusion that
unsaturated hydraulic conductivity of sandy loam soil is greater than the clay soil.
