MODELLING SOIL MOISTURE FLOW AND SOLUTE TRANSPORT THROUGH VADOSE ZONE OF GWALIOR, INDIA

Abstract

The sub-surface solute and moisture flow at any particular site is governed by the prevailing hydrogeological conditions of that area. In the present study an effort has been made to consider these conditions using a mechanistic model to study the behavior of moisture movement and solute migration to the underlying groundwater resources. The area of study is the Gwalior District of MP having total area of 780 km2. Simulation employs the universally used Richards equation for moisture flow through the vadose zone and fickian based adjective-dispersive equation for solute transport. Seven sites namely BEHAT, MAGRORA, SULAKHARI, SIRSULA, RAMPRASADPURA, BERJA, JORASI having detailed lithologs are selected for simulating the subsurface movement of applied pollutant. The physical and hydraulic parameters used in the modeling like moisture content, hydraulic conductivity, curve fitting parameters etc. used in this modeling are representative of actual subsurface conditions of the study domain to replicate the natural process closely. Conventionally, uniform flow is considered for predicting soil moisture and contaminant transport through vadose zone considering it as a completely homogeneous zone. However preferential flow takes place due to heterogeneous nature of the soil profile in real field conditions. Therefore, in this study, simulation runs are carried out for the vadose zone of Gwalior district considering preferential flow. For comparative analysis, both single and dual porosity approaches are considered under constant flux and atmospheric boundary conditions using Hydrus 1d. ArcGIS is used for preparing vulnerability maps using the simulated time required by the applied solute to traverse from surface to the groundwater table. The obtained vulnerability maps provide the general idea of all the considered locations against contamination in Gwalior. It was found that Berja is highly vulnerable under constant as well the atmospheric Boundary condition and Jorasi falls under the least vulnerable zone to contamination under both conditions. The findings of this study may assist in planning of Industrial locations and for sustainable development of ground water resources of Gwalior district.