Modelling of soil moisture movement and solute transport in an agriculture field - A case study

Pollution of ground water due to agricultural activities is probably the most difficult to model because it is governed by physical and chemical phenomena which need intensive field and laboratory investigations. Problem becomes more complicated when dealing with different kinds of soil with varying properties. Therefore, in the present study, an attempt has been made to understand the soil moisture movement and solute transport in different soils (black cotton and red soil) in two agricultural plots in Malaprabha catchment in Belgaum district, Karnataka. Soil hydrological parameters such as infiltration, hydraulic conductivity and moisture profiles were measured in the field during pre-monsoon and post-monsoon period. Soil moisture retention characteristics were determined in the laboratory using pressure plate apparatus. Data pertaining to application of fertilizers and their chemical constituent were obtained from the state agencies. Ground water recharge from rainfall has been computed using SWIM model. It is based on a numerical solution of the Richard's equation and the advection-dispersion equation, which can be used to simulate runoff, infiltration, redistribution, solute transport, deep drainage and leaching. Simulated soil moisture and solute concentration profiles during pre-monsoon and post-monsoon seasons were found to match reasonably with observed profiles. The model can therefore be used to predict the solute concentration profiles at different time scenarios in response to pre-determined application of fertilizers.