Donald A. Walter Jennifer G. Savoie John P. Masterson 1996 <p>A steady-state, three-dimensional numerical model coupled with a particle-tracking algorithm was developed to simulate the complex hydrogeologic conditions affecting ground-water flow and contaminant migration in the Cape Cod aquifer beneath the Massachusetts Military Reservation, Massachusetts. The known extents of the contaminant plumes beneath the reservation were incorporated into a particle-tracking analysis to improve model calibration. Particle tracking was used to evaluate the effects of simulated changes in hydraulic properties and in simulated hydrologic boundaries such as ponds and streams.</p><p>The model simulations made during the calibration process indicated that changes in simulated hydraulic properties and hydrologic boundaries resulted in small changes in the water-table and pond altitudes and in streamflows, yet had a substantial effect on model-calculated groundwater flowpaths. Therefore, the characterization of contaminant migration using a model calibrated only on the basis of ground-water heads and flux may be inaccurate.</p><p>The results of model simulations for the analysis of the effects of pumping and recharge on ground-water flow and contaminant migration indicated that ground-water flowpaths were greatly affected by subtle shifts in hydraulic gradients. These changes in the ground-water-flow system in response to hydrologic stresses such as pumping and recharge can be determined by the use of a particle-tracking analysis.</p> application/pdf 10.3133/ofr96214 en U.S. Geological Survey Use of particle tracking to improve numerical model calibration and to analyze ground-water flow and contaminant migration, Massachusetts Military Reservation, western Cape Cod, Massachusetts reports