Radial Flow Tracer Test to Investigate Coefficient of Transverse Dispersion in an Aquifer in the Eastern Niger Delta, Nigeria

The complex nature of flow dynamic of water at the subsurface makes it difficult to characterize directly the processes taking place in a porous medium. As a result, carrying out studies on the characteristics of contaminants at the subsurface often relies on indirect measurements of the parameters of the system. To overcome these difficulties and provide information on the subsurface, the continuous use of tracers in simulation studies to model hydrological characteristics at the subsurface has provided an important tool for understanding the flow and mixing dynamics of water resource systems. Results obtained from this radial flow tracer test shows coefficient of longitudinal and transverse dispersion of 2.104×10-3 m2s-1 and 1.54×10-3 m2s-1 respectively, longitudinal and transverse dispersivity of 1.73m and 1.27m respectively. Multidimensional transport in an aquifer involves both longitudinal and transverse dispersion in addition to advection process. Transverse dispersion in an aquifer spreads dissolved contaminant by molecular diffusion when flow velocity of groundwater is highly low. Initial concentration of dissolved contaminants at the point of release can produce an upstream spreading in a longitudinal transverse direction by molecular dispersion which is a diffusion-like process in an aquifer. Results obtained from tracer test can be used to characterize a site and for groundwater monitoring. Having basic knowledge of some physical processes taking place at the subsurface such as that produced from tracer test can also help in the design of environmental network to evaluate possible accidental migration of contaminants once it occur in aquifers and plan suitable mitigation actions to safeguard our water resource.