Groundwater Vulnerability Assessment to Contamination Using Soil Moisture Flow and Solute Transport Modeling

Abstract

The soil moisture flow and solute transport regimes of the vadose zone associated with specific hydrogeological conditions play a crucial role in pollution risk assessment of the underlying groundwater resources. An effort has been made to map the vulnerability of shallow groundwater to surface pollutants of Doon Valley, an intermontane watershed in North India situated between the lesser Himalayas and Shiwalik ranges, using soil moisture flow and contaminant transport modeling. The classical advection dispersion equation coupled with the Richard’s equation is numerically simulated at different point locations for assessing the intrinsic vulnerability of the valley. The role of soil type, slope, and land-use cover is considered for estimating the transient flux at the top boundary from daily precipitation and evapotranspiration data of the study area. The time required by solute peak to travel from the surface to the groundwater table at the bottom of the soil profile is considered as an indicator of vulnerability index. Results show a high vulnerability in the southern region, whereas low vulnerability is observed in the northeast and northern parts of the valley. These findings are in line with the observed low water table depths, less runoff, and higher hydraulic conductivity of the vadose zone material in the southern part of the valley. The study may assist in decision making related to planning of industrial locations and the sustainable water resources development of the valley.