Digital Model of Alluvial Aquifer

The evaluation of an alluvial aquifer as a water supply for the Town of Antigonish, Nova Scotia, has demonstrated the versatility of the digital model as a tool in groundwater development and management. The digital model, which uses an alternating-direction implicit technique to solve the finite-difference approximation of the flow equation, is limited in size only by the available hydrogeologic data, the amount of computer storage, and availability of computer time. The model of the Antigonish aquifer, which is hydraulically connected to a river, was adjusted within the constraints dictated by the geology until the model response to a pumping stress approached the field response. The most critical factor was the river-bed hydraulic conductivity to thickness ratio which governs the drawdown required to induce enough water from the river to sustain well production. The adjusted model was used to predict the effect of establishing a multiple well field designed to meet the town's requirements.