Numerical simulation of groundwater flow and advective transport in an unconfined aquifer : a case study

Abstract

For an agricultural groundwater research site in Hoyt, New Brunswick, the properties of the unconfined aquifer were determined and a numerical model was created. The project objective was to develop a model of groundwater flow and advective transport that can be used to simulate the migration of pesticides and herbicides in the shallow aquifer. Pneumatic slug tests were conducted to determine the hydraulic conductivity at 19 piezometers located at the project site. Water levels were recorded at 23 these piezometers over a period of 16 months and the mean water level was calculated for each location. Using the computer program Flowpath II®, the field data was plotted and a finite-difference numerical model was created. The model was calibrated by varying the hydraulic conductivity coverage at the edges of the model and reiterating this procedure until the model best matched the actual field data. This model was then used to predict travel times for solutes in the shallow aquifer below the field site. It was found that travel times closely matched actual field data.